United States of America v. Okello T. Chatrie

Certiorari granted by Supreme Court, January 20, 2026
ON REHEARING EN BANC
PUBLISHED
UNITED STATES COURT OF APPEALS
FOR THE FOURTH CIRCUIT
No. 22-4489
UNITED STATES OF AMERICA,
Plaintiff − Appellee,
v.
OKELLO T. CHATRIE,
Defendant – Appellant.
------------------------------
THE REPORTERS COMMITTEE FOR FREEDOM OF THE PRESS; AMERICAN
CIVIL LIBERTIES UNION; AMERICAN CIVIL LIBERTIES UNION OF
VIRGINIA; EIGHT FEDERAL PUBLIC DEFENDER OFFICES WITHIN THE
FOURTH CIRCUIT; TECHNOLOGY LAW AND POLICY CLINIC AT NEW
YORK UNIVERSITY SCHOOL OF LAW; ELECTRONIC FRONTIER
FOUNDATION,
Amici Supporting Appellant.
PROJECT FOR PRIVACY AND SURVEILLANCE ACCOUNTABILITY, INC.,
Amicus Supporting Rehearing Petition.
Appeal from the United States District Court for the Eastern District of Virginia, at
Richmond. M. Hannah Lauck, District Judge. (3:19−cr−00130−MHL−1)
Argued: January 30, 2025 Decided: April 30, 2025

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Before DIAZ, Chief Judge, and WILKINSON, NIEMEYER, KING, GREGORY, AGEE,
WYNN, THACKER, HARRIS, RICHARDSON, QUATTLEBAUM, RUSHING,
HEYTENS, BENJAMIN, and BERNER, Circuit Judges.
Affirmed by published per curiam opinion in which Chief Judge Diaz, Judge Wilkinson,
Judge Niemeyer, Judge King, Judge Agee, Judge Wynn, Judge Thacker, Judge Harris,
Judge Richardson, Judge Quattlebaum, Judge Rushing, Judge Heytens, Judge Benjamin,
and Judge Berner joined.
Chief Judge Diaz wrote a concurring opinion. Judge Wilkinson wrote a concurring
opinion, in which Judge Niemeyer, Judge King, Judge Agee, and Judge Richardson joined.
Judge Niemeyer wrote a concurring opinion. Judge King wrote a concurring opinion.
Judge Wynn wrote a concurring opinion, in which Judge Thacker, Judge Harris, Judge
Benjamin, and Judge Berner joined in full, and in which Judge Gregory joined except as to
footnote 1. Judge Richardson wrote a concurring opinion, in which Judge Wilkinson,
Judge Niemeyer, Judge King, Judge Agee, Judge Quattlebaum, and Judge Rushing joined.
Judge Heytens wrote a concurring opinion, in which Judge Harris and Judge Berner joined.
Judge Berner wrote a concurring opinion, in which Judge Gregory, Judge Wynn, Judge
Thacker, and Judge Benjamin joined in full, and in which Judge Heytens joined as to Parts
I, II(A), and II(B).
Judge Gregory wrote a dissenting opinion.
ARGUED: Michael William Price, NATIONAL ASSOCIATION OF CRIMINAL
DEFENSE LAWYERS, Washington, D.C., for Appellant. Nathan Paul Judish, UNITED
STATES DEPARTMENT OF JUSTICE, Washington, D.C., for Appellee. ON BRIEF:
Geremy C. Kamens, Federal Public Defender, Alexandria, Virginia, Laura J. Koenig,
Assistant Federal Public Defender, OFFICE OF THE FEDERAL PUBLIC DEFENDER,
Richmond, Virginia, for Appellant. Kenneth A. Polite, Jr., Assistant Attorney General,
Richard W. Downing, Deputy Assistant Attorney General, UNITED STATES
DEPARTMENT OF JUSTICE, Washington, D.C.; Jessica D. Aber, United States Attorney,
Kenneth R. Simon, Jr., Assistant United States Attorney, Peter S. Duffey, Assistant United
States Attorney, OFFICE OF THE UNITED STATES ATTORNEY, Richmond, Virginia,
for Appellee. Jennifer Lynch, Andrew Crocker, Hannah Zhao, ELECTRONIC FRONTIER
FOUNDATION, San Francisco, California; Jacob M. Karr, Technology Law and Policy
Clinic, NEW YORK UNIVERSITY SCHOOL OF LAW, New York, New York, for Amici
Technology Law and Policy Clinic at New York University School of Law. Jennifer Stisa
Granick, San Francisco, California, Nathan Freed Wessler, Ashley Gorski, Patrick Toomey,
Brandon Buskey, Trisha Trigilio, Laura Moraff, Brett Max Kaufman, AMERICAN CIVIL
LIBERTIES UNION FOUNDATION, New York, New York; Eden B. Heilman, Matthew
W. Callahan, AMERICAN CIVIL LIBERTIES UNION FOUNDATION OF VIRGINIA,

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Richmond, Virginia; William F. Nettles, IV, Federal Public Defender, Columbia, South
Carolina, G. Alan Dubois, Federal Public Defender, Raleigh, North Carolina, Louis Allen,
Federal Public Defender, Greensboro, North Carolina, Juval O. Scott, Federal Public
Defender, Roanoke, Virginia, Brian J. Kornbrath, Federal Public Defender, Clarksburg,
West Virginia, John Baker, Federal Public Defender, Charlotte, North Carolina, James
Wyda, Federal Public Defender, Baltimore, Maryland, Wesley P. Page, Federal Public
Defender, OFFICE OF THE FEDERAL PUBLIC DEFENDER, Charleston, West Virginia,
for Amici American Civil Liberties Union, American Civil Liberties Union of Virginia, and
Eight Federal Public Defender Offices Within the Fourth Circuit. Bruce D. Brown, Katie
Townsend, Gabe Rottman, Grayson Clary, Emily Hockett, REPORTERS COMMITTEE
FOR FREEDOM OF THE PRESS, Washington, D.C., for Amicus The Reporters
Committee for Freedom of the Press. Gene C. Schaerr, Erik S. Jaffe, Aaron C. Ward,
SCHAERR | JAFFE LLP, Washington, D.C., for Amicus Project for Privacy &
Surveillance Accountability, Inc.

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PER CURIAM:
The judgment of the district court is
AFFIRMED.

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DIAZ, Chief Judge, concurring:
I join in affirming the district court’s denial of Okello Chatrie’s suppression motion,
but solely on the court’s finding of good faith. See United States v. Chatrie, 590 F. Supp.
3d 901, 936–41 (E.D. Va. 2022). My colleagues have widely divergent views on the
intersection of the Fourth Amendment and the groundbreaking investigative tool at issue
here. I respect the care and attention they’ve devoted to this matter. But judicial modesty
sometimes counsels that we not make grand constitutional pronouncements merely because
we can.
This is such a case.
I.
A.
Today we consider the constitutionality of geofence warrants, a novel and powerful
technology that law enforcement has increasingly used to investigate crime. In simple
terms, a geofence warrant requires a service provider to produce location data from cell
phone users who were near the scene when a crime occurred.
Like a traditional warrant, law enforcement (as here) may apply for a geofence
warrant from a judge. If granted, law enforcement can then serve the warrant on the
provider (here, Google).1
1 The district court explained: “Other companies such as Amazon and Apple
invariably retain users’ location data as well. But Google, whose services function across
Apple and Android devices . . . , seems to be subject to more geofence requests than other

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Google collects the Location History of over 500 million users, and it’s this data
that law enforcement accesses via a geofence warrant. Location History “appears to be the
most sweeping, granular, and comprehensive tool—to a significant degree—when it comes
to collecting and storing location data.” Chatrie, 590 F. Supp. 3d at 907 (emphasis
omitted).
It’s also remarkably extensive, “log[ging] a device’s location, on average, every two
minutes,” even “in terms of elevation.” Id. at 908. If a device is in a building, for example,
its Location History can show on which floor.
When presented with a geofence warrant, Google applies an internally developed
three-step process, providing to law enforcement an anonymous “list of all Google users
whose Location History data indicates were within the geofence during a specified
timeframe.” Id. at 915 (cleaned up). To do this, “Google must search all Location History
data to identify users,” regardless of whether the users “saved Location History data.” Id.
(cleaned up).2 After narrowing the list to users who had their Location History enabled,
Google also provides “the date and time, the latitude and longitude, the geolocation source
companies.” Chatrie, 590 F. Supp. 3d at 907 n.8. What’s more, “[c]ompanies such as
Apple, Lyft, Snapchat, and Uber have all received geofence warrant requests, but Google
is the most common recipient and ‘the only one known to respond.’” United States v.
Smith, 110 F.4th 817, 821 n.2 (5th Cir. 2024) (cleaned up).
2 Location History “is off by default” on a cell phone, though it’s “‘possible that a
user would have seen the option’ to opt into Location History multiple times across
multiple apps.” Id. at 908–09.

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used, and the map display radius (i.e., the confidence interval)” for the relevant accounts.
United States v. Smith, 110 F.4th 817, 824–25 (5th Cir. 2025).
At the second step, law enforcement may “compel Google to provide additional
location coordinates beyond the time and geographic scope of the original request,”
ostensibly to “assist . . . in eliminating devices.” Chatrie, 590 F. Supp. 3d at 916 (cleaned
up). But while law enforcement may widen the geographic scope of the request, Google
“typically require[s] law enforcement to narrow the number of users for which it requests
[additional] data.” Id.
Finally, at the third step, law enforcement “‘can compel Google to provide account-
identifying information’ for the users ‘the [g]overnment determines are relevant to the
investigation.’” Id. (cleaned up). “This ‘account-identifying information’ includes the
name and email address associated with [an] account.” Id.
B.
The police charged Chatrie with two crimes related to a bank robbery based on
information obtained from Google through a geofence warrant. Detective Joshua Hylton
prepared the warrant, which “drew a geofence with a 150-meter radius—with a diameter
of 300 meters, longer than three football fields—in an urban environment.” Id. at 918.
That radius included the bank and a nearby church. Id. The warrant “sought location data
for every device present within the geofence” for an hour around the time of the robbery
(i.e., thirty minutes before and thirty minutes after). Id. at 919.

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In the warrant, Detective Hylton described Google’s three-step process, explaining
that he would “‘attempt to narrow down’ the list of users for which the [g]overnment would
obtain the most invasive information.” Id.
First, the warrant directed Google to “‘provide “anonymized information” regarding
the Accounts that are associated with a device that was inside the described geographical
area’” in the hour around the robbery. Id. Next, “[l]aw enforcement would return a list of
accounts that they had attempted to narrow down,” so that “Google would then ‘produce
contextual data points with points of travel outside of the geographical area.” Id. (cleaned
up). To do so, “the warrant expanded the timeframe to include thirty minutes before and
thirty minutes after the initial hour-long window”—covering a two-hour total window. Id.
Finally, law enforcement would direct Google to provide identifying information for
certain accounts.
In his affidavit supporting the warrant, Hylton added that the geofence process could
identify not only the robber but also “potential witnesses and/or [other] suspects.” Id. at
920. This was because the detective had observed on surveillance footage that the robber
“had a cell phone in his right hand and appeared to be speaking with someone else on the
device”—someone with whom the robber may have been “act[ing] in concert.” Id. Using
the warrant and the subsequent information Google provided, law enforcement identified
Chatrie as a suspect.
After his arrest, Chatrie, who had opted to share his Location History with Google,
moved to suppress the location information, arguing that the warrant violated the Fourth
Amendment. The district court agreed that this geofence warrant “plainly violate[d]” the

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Constitution,3 id. at 905, but nonetheless declined to suppress it under the good-faith
exception to the Fourth Amendment, id. at 936–41.
The district court emphasized that “evidence obtained pursuant to a search warrant
issued by a neutral magistrate need not be excluded if the officer’s reliance on the warrant
was ‘objectively reasonable.’” Id. at 937 (cleaned up). Ticking through the factors the
Supreme Court outlined in United States v. Leon, 468 U.S. 897 (1984), that we have since
applied, see, e.g., United States v. Doyle, 650 F.3d 460, 467 (4th Cir. 2011), the district
court found that the instant warrant passed the good-faith bar. Chatrie, 590 F. Supp. 3d at
937.
When Detective Hylton applied for the geofence warrant in this case, no court had
ruled on the legality of such warrants generally. So he relied on his experience, having
successfully obtained three other geofence warrants after consulting with prosecutors
before seeking them. Id. at 938.
Hylton also obtained approval from a state magistrate for the warrant. See id. at
938–39. To be sure, neither the detective nor the magistrate performed their duties
perfectly.
Inexplicably, Detective Hylton submitted a search warrant return—which “notifies
the Court when an officer executes a search warrant” and describes “what items [the
3 The Fifth Circuit has held “that geofence warrants are general warrants
categorically prohibited by the Fourth Amendment.” Smith, 110 F.4th at 838. But like the
district court here, the Fifth Circuit in Smith declined to suppress the challenged warrant
on good-faith grounds. Id. at 838–40.

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officer] gathered during the search”—to the magistrate before he had even served the
warrant on Google. Id. at 920. In that return, Hylton “stated that he had executed the
warrant,” even though, again, he hadn’t yet sent it to Google. Id. And he wrote that he
had seized “Data,” when, in fact, he seized “what would be a sizable amount of precise
location information on at least nineteen device users.” Id. (cleaned up).
As for the magistrate, he “asked no questions” of Detective Hylton. Nor did he
“seek to modify anything” in the accompanying affidavit, even though this appears to be
the first geofence warrant application the magistrate had considered. Id. at 918.
Still, the district court was satisfied that the warrant was “not so lacking in indicia
of probable cause as to render official belief in its existence entirely unreasonable.” Id. at
937 (cleaned up). The good-faith exception thus saved the warrant from suppression.
I would adopt that narrow holding here.
II.
A.
Geofence warrants are an extraordinary investigatory advancement, born out of
technological developments enabling the relentless collection of eerily precise location
data. But questions remain about the technology enabling such warrants as well as
Google’s process for responding to them. It’s no mystery then that applying our legal
precedents to this rapidly evolving technology is precarious. Indeed, as the district court
noted, “[t]his case implicates the next phase in the courts’ ongoing efforts to apply the

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tenets underlying the Fourth Amendment to previously unimaginable investigatory
methods.” Chatrie, 590 F. Supp. 3d at 905.
Earlier cases applied the Fourth Amendment to “recording devices in public
telephone booths,” “thermal-imaging equipment” aimed at homes, “and, most recently, to
cell-site location data.” Id. (summarizing cases). The cases have protected “data that
provides an intimate window into a person’s life, revealing not only his particular
movements, but through them his ‘familial, political, professional, religious, and sexual
associations,’” if that data hasn’t been meaningfully disclosed to a third party. Carpenter
v. United States, 585 U.S. 296, 311, 314–15 (2018).4
We’ve then used this precedent to “solidif[y] the line between short-term tracking
of public movements—akin to what law enforcement could do prior to the digital age—
and prolonged tracking that can reveal intimate details through habits and patterns.”
Leaders of a Beautiful Struggle v. Balt. Police Dep’t, 2 F.4th 330, 341 (4th Cir. 2021) (en
banc) (cleaned up). The latter “invades the reasonable expectation of privacy that
individuals have in the whole of their movements and therefore requires a warrant.” Id.
4 The Court opined that whether and how the Fourth Amendment applied to cell-
site records existed “at the intersection of two lines of cases, both of which inform[ed] [its]
understanding of the privacy interests at stake.” 585 U.S. at 306. “The first set of cases”—
including United States v. Knotts, 460 U.S. 276 (1983), and United States v. Jones, 565
U.S. 400 (2012)—“address[ed] a person’s expectation of privacy in his physical location
and movements.” Carpenter, 585 U.S. at 306–07. “In a second set of decisions”—
including Smith v. Maryland, 442 U.S. 735 (1979)—“the Court [drew] a line between what
a person keeps to himself and what he shares with others,” which is the guiding principle
for the third-party doctrine. Carpenter, 585 U.S. at 307–09.

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Still, the Supreme Court has recognized that our existing Fourth Amendment
frameworks—like the third-party doctrine—may be “ill suited to the digital age,” United
States v. Jones, 565 U.S. 400, 417–18 (2012) (Sotomayor, J., concurring), particularly
when applied to cell phones, which can enable law enforcement to “achieve[] near perfect
surveillance,” Carpenter, 585 U.S. at 312.5 On top of that, cell phones have become
“almost ‘a feature of human anatomy’” that individuals “compulsively carry . . . with them
all the time.” Id. at 311 (cleaned up).
So what happens when (as here) there are serious questions about the scope of a
defendant’s consent to a third-party’s use of his data given the breadth of the third party’s
“detailed, encyclopedic, and effortlessly compiled” data collection methods? Id. at 309;
see also id. at 315 (commenting that exposure of data may not be meaningfully voluntary
when the user doesn’t “‘assume the risk’ of turning over a comprehensive dossier of his
physical movements” (cleaned up)). Or when (again as here) a “brief snapshot” of location
information, even if it doesn’t capture a pattern, still “expose[s] highly sensitive
information—think a visit to ‘the psychiatrist, the plastic surgeon, the abortion clinic, the
AIDS treatment center, the strip club . . . , [or] the mosque, synagogue[,] or church’”?
Smith, 110 F.4th at 833 (cleaned up); see also Carpenter, 585 U.S. at 311 (“A cell phone
5 Even Google—in an amicus brief—argued “that a geofence is certainly a ‘“search”
within the meaning of the Fourth Amendment’ because ‘users have a reasonable
expectation of privacy in the [Location History] information, which the government can
use to retrospectively reconstruct a person’s movements in granular detail.’” Chatrie, 590
F. Supp. 3d at 907 n.5 (cleaned up).

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faithfully follows its owner beyond public thoroughfares and into private residences,
doctor’s offices, political headquarters, and other potentially revealing locales.”).
Despite the district court’s best efforts to develop the record, our understanding of
Google’s data collection policy and its internal geofence warrant process remains imperfect
and incomplete.6 It’s no surprise then that the parties vigorously debate—as my colleagues
do—the potentially sweeping implications of any decision.
One camp insists that disallowing geofence warrants would contravene our
precedent, hamstring law enforcement in investigating crimes, and chill innovation at any
private company that handles a large database of users. The other camp is just as adamant
that granting blanket approval to these warrants would contravene our precedent and
compromise the privacy interests of cell phone users.
The balance, ever so delicate, swings from law enforcement and public safety to
liberty and privacy interests depending on the record facts. Yet despite a shallow well of
information and legal authority and a litany of unanswered questions as to our decision’s
6 To add more uncertainty, Google intends to change its Location History policy so
that it will no longer be able to respond to geofence warrants. See Smith, 110 F.4th at 822
n.3.; see also Marlo McGriff, Updates to Location History and New Controls Coming
Soon to Maps, Google (Dec. 12, 2023), https://blog.google/products/maps/updates-to-
location-history-and-new-controls-coming-soon-to-maps/ [https://perma.cc/7ZMS-
RHF9].

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reach, my colleagues choose to write broadly. At least in this case, I would opt for restraint
and rest on the good-faith exception to the Fourth Amendment.7
B.
The good-faith exception is reason enough to affirm the district court without
stunting our ability to respond down the line to Fourth Amendment issues that are presently
“unimaginable.” Chatrie, 590 F. Supp. 3d at 905. Arising out of the exclusionary rule, the
exception broadly queries the deterrent benefits of suppressing an otherwise
constitutionally infirm search. See, e.g., Davis v. United States, 564 U.S. 229, 236–37
(2011).
Generally, “[t]o trigger the exclusionary rule, police conduct must be sufficiently
deliberate that exclusion can meaningfully deter it, and sufficiently culpable that such
deterrence is worth the price paid by the justice system.” Herring v. United States, 555
U.S. 135, 144 (2009). And ‘“[u]sually, ‘a warrant issued by a magistrate . . . suffices to
establish’” that a law enforcement officer has “acted in good faith in conducting the
search.” Doyle, 650 F.3d at 467 (quoting Leon, 468 U.S. at 922).
To better measure any deterrent benefits, courts consider four circumstances in
which good faith won’t shield even a search made pursuant to a warrant:
(1) If the magistrate or judge in issuing a warrant was misled by information
in an affidavit that the affiant knew was false or would have known was false
7 See, e.g., Ashwander v. Tenn. Valley Auth., 297 U.S. 288, 347 (1936) (Brandeis,
J., concurring) (“The Court will not pass upon a constitutional question although properly
presented by the record, if there is also present some other grounds upon which the case
may be disposed of.”); Camreta v. Greene, 563 U.S. 692, 707 (2011) (“In general, courts
should think hard, and then think hard again, before turning small cases into large ones.”).

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except for his reckless disregard of the truth; (2) if the issuing magistrate
wholly abandoned his judicial role . . . ; (3) if the affidavit supporting the
warrant is so lacking in indicia of probable cause as to render official belief
in its existence entirely unreasonable; and (4) if under the circumstances of
the case the warrant is so facially deficient—i.e., in failing to particularize
the place to be searched or the things to be seized—that the executing officers
cannot reasonably presume it to be valid.
Id. at 467 (cleaned up). None defeat good faith here.
As to the first, Hylton’s occasional sloppiness aside, there’s no evidence that Hylton
gave false information to the magistrate when seeking the geofence warrant. And I agree
with the government that Chatrie expressly disclaimed any challenge under Franks v.
Delaware, 438 U.S. 154 (1978), that Detective Hylton “intentionally or recklessly omitted
material information from the affidavit.” See Appellee’s Br. at 50 (quoting United States
v. Pulley, 987 F.3d 370, 376 (4th Cir. 2021)); see also Appellant’s Br. at 11 n.2.
Nor is there evidence that the magistrate didn’t review the warrant application and
Hylton’s affidavit before issuing the warrant, or that the magistrate at any time
“overstepped his . . . judicial responsibilities and compromised his judicial neutrality.”
Chatrie, 590 F. Supp. 3d at 938 (cleaned up). Chatrie’s citation to Lo-Ji Sales, Inc. v. New
York, 442 U.S. 319 (1979), in which the magistrate became “a member, if not the leader,
of the search party which was essentially a police operation,” id. at 327, is a far cry from
the magistrate’s performance here.
At best, Chatrie has “perhaps[] shown that [the magistrate] should have considered
the implications of the [w]arrant more carefully.” Chatrie, 590 F. Supp. 3d at 938. But
our standard for good faith is not so exacting. The magistrate remained a neutral authority

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who reviewed a warrant application describing a novel investigative tool with a “dearth of
court precedent to follow.” Smith, 110 F.4th at 840.8
Chatrie’s fight isn’t really with the police or the magistrate. Rather than allege any
malfeasance by either, Chatrie repackages his attack on the warrant’s probable cause and
particularity to suggest that both acted in bad faith. See, e.g., Appellant’s Br. at 29–30, 32–
33, 38–39. He argues that the warrant was “‘completely devoid’ of probable cause,” id. at
23, and so “profoundly lacking in particularity,” id. at 34, as to render it a “despised” (and
illegal) general warrant, id. at 35.
A few points bear repeating. Hylton reviewed surveillance footage showing that the
robber used a cell phone, so he knew that a geofence could reveal both the robber’s identity
and any potential co-conspirators. The detective also limited the warrant geographically
and temporally. Hylton, of course, could have further limited the warrant to a smaller
radius around the Bank or a closer time to the robbery. But given the “dearth of . . .
precedent to follow,” Smith, 110 F.4th at 840, nothing required or cautioned him to do so.
Without any directly governing case law, Hylton understandably relied on the
previous guidance he had been given, which is, as my colleague explains, “what we expect
reasonable officers to do when faced with such uncertainty.” Opinion of HEYTENS, J., at
87 (concurring). Magistrates and prosecutors had approved three of Hylton’s “mostly
similar” prior warrants—“all but one [of which] incorporated a roughly 150-meter radius.”
8 Despite holding that geofence warrants are categorically unconstitutional general
warrants, our sister circuit declined to suppress the evidence under the good-faith
exception. Smith, 110 F.4th at 840.

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Chatrie, 590 F. Supp. 3d at 938. As the district court found, “[e]ven accounting for his
miscues, in light of the complexities of this case, Det[ective] Hylton’s prior acquisition of
three similar warrants, and his consultation with [g]overnment attorneys before obtaining
those warrants, the [c]ourt cannot say that [his] reliance on the instant warrant was
objectively unreasonable.” Id. (emphasis added).
Chatrie insists that even a warrant “cloaked” in new technology must still be
supported by probable cause and be sufficiently particularized as to the places to be
searched and things to be seized. Appellant’s Br. at 24. I agree with him. But Detective
Hylton limited the places to be searched—both by geography and time—as well as the
location information to be seized—to those cell phone users within the parameters of the
geofence warrant.
To the extent that Chatrie complains that law enforcement didn’t know his identity
in seeking the warrant (or until well into Google’s three-step process), I’m not persuaded
that carries the day, especially when assessing good faith. For many warrants, after all, the
point is to identify a suspect, which is why the warrant requirement focuses on the places
to be searched and things to be seized. See Zurcher v. Stanford Daily, 436 U.S. 547, 555
(1978) (“Search warrants are not directed at persons; they authorize the search of ‘places’
and the seizure of ‘things,’ and as a constitutional matter they need not even name the
person from whom the things will be seized.” (cleaned up)).
Take Zurcher v. Stanford Daily, 436 U.S. 547, in which law enforcement executed
a search warrant of the student newspaper’s offices to seize “negatives, film, and pictures
showing the events and occurrences at the [Stanford University Hospital] on the evening”

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that demonstrators allegedly assaulted police officers. Id. at 551. Law enforcement
secured the warrant “on a finding of ‘just, probable and reasonable cause for believing
that’” the things seized—negatives, photographs, and films—would reveal “evidence
material and relevant to the identity of the perpetrators.” Id. And the warrant was issued
even though the affidavit “contained no allegation or indication that members of the Daily
staff were in any way involved in unlawful acts at the hospital.” Id.
No doubt, the initial search here of over 500 million cell phone users is—to put it
mildly—broader than the search of a handful of college students, but both warrants were
issued to help identify the suspect of the crime. And in this case, law enforcement narrowed
down the list of potential perpetrators at each step of the process from millions to dozens
to a few based on the other relevant evidence. That rings in probable cause sufficient for
me to find good faith.
Geofence warrants may differ from traditional warrants, working in reverse by
specifying the time and place of a crime rather than the identity of the perpetrator, but that
doesn’t automatically render them “facially deficient,” Doyle, 650 F.3d at 467 (cleaned
up). Indeed, most Internet or mass database searches would be cut from the same cloth.
All this is to say that it’s not clear what conduct suppression of the evidence would
“meaningfully deter” here. Herring, 555 U.S. at 144; accord Chatrie, 590 F. Supp. 3d at
938. Whatever the warrant’s shortcomings, I agree with the district court that the warrant
wasn’t “so lacking in indicia of probable cause” as to justify suppressing it here. Chatrie,
590 F. Supp. 3d at 937 (cleaned up).

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III.
When confronted with another opaque and “transformative” piece of technology,
the Supreme Court recently reminded us that
[t]his challenging new context counsels caution on our part. As Justice
Frankfurter advised 80 years ago in considering the application of established
legal rules to the “totally new problems” raised by the airplane and radio, we
should take care not to “embarrass the future.”
TikTok Inc. v. Garland, 145 S. Ct. 57, 62 (2025) (per curiam) (cleaned up).
My colleagues have done their level best to cut through the Fourth Amendment fog
in this case. In contrast, some may say that I’ve done nothing more today than kick the
geofence warrant can down the road. Others may complain that I’ve offered no guidance
to law enforcement and magistrates about the reach of the Fourth Amendment in the digital
age, or worse still, that I’ve resorted to “judicial abdication,” opinion of WYNN, J., at 35
(concurring).
But what guidance have my colleagues given today? Instead of a Fourth
Amendment compass, we’ve gifted law enforcement (and the public) a labyrinth of—by
my count, nine—advisory opinions, many pointing in different directions.9 See, e,g., Riley
v. California, 573 U.S. 373, 398 (2014) (expressing a “preference” for “provid[ing] clear
guidance to law enforcement” under the Fourth Amendment); Felix Frankfurter, A Note on
9 Even the Fifth Circuit’s opinion, though issued in one voice, has left legal scholars
concerned about its fidelity to the Supreme Court’s Fourth Amendment precedent, and its
implications for all manner of law enforcement investigative tools. See, e.g., Orin S. Kerr,
The Fifth Circuit Shuts Down Geofence Warrants—And Maybe a Lot More, The Volokh
Conspiracy (August 13, 2024), https://reason.com/volokh/2024/08/13/fifth-circuit-shuts-
down-geofence-warrants-and-maybe-a-lot-more/ [https://perma.cc/3G5V-WE7F].

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Advisory Opinions, 37 Harv. L. Rev. 1002, 1008 (1942) (“It must be remembered that
advisory opinions are not merely advisory opinions. They are ghosts that slay.”). I don’t
see the utility in that, as it assumes (wrongly) that we must give a full answer now.
In short, there are times to make sweeping constitutional pronouncements (with
attendant consequences) and times to wait. Humility in the face of the unknown—whether
it be the legal ramifications or practical consequences of our decision, or Google’s own
changing policies—“counsels caution.” TikTok, Inc., 145 S. Ct. at 62.
* * *
A brief coda. I expect law enforcement to exercise good faith in using powerful,
revolutionary technologies to investigate crimes, and, indeed, that their first instinct will
be to use and not abuse the information this technology reveals. And I echo the district
court’s warning that “[d]espite . . . finding good faith here, . . . this exception may not carry
the day in the future.” Chatrie, 590 F. Supp. 3d at 941.
By my measure, today “our judicial obligation” can “be captured by a much older
rule, familiar to every doctor of medicine: ‘First, do no harm.’” Denver Area Educ.
Telecomms. Consortium, Inc. v. F.C.C., 518 U.S. 727, 778 (1996) (Souter, J., concurring).

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WILKINSON, Circuit Judge, with whom NIEMEYER, KING, AGEE, and
RICHARDSON, Circuit Judges, join, concurring:
With due regard for my fine colleagues, there was no search here. And even if one
were to assume there was a search, there are many good reasons why courts should
respectfully reject the assault on geofence warrants mounted by appellant, several of my
colleagues, see opinion of WYNN, J. (concurring), and the Fifth Circuit Court of Appeals,
see United States v. Smith, 110 F.4th 817 (5th Cir. 2024).
I.
There was no search because this case involved a straightforward application of
Smith, 442 U.S. 735 (1979), and Miller, 425 U.S. 435 (1976). Just like in those cases,
Chatrie volunteered incriminating information about himself to a third party. His
expectation of privacy was comparatively small. Miller, for instance, involved months of
financial transaction history, which undeniably exposes many intimacies of one’s life. If
that request for bank records was permissible, surely this request for a two-hour snapshot
of one’s public movements, which hardly reveals one’s habits, is okay.
There are many good reasons why the Supreme Court did not discard the third-party
doctrine for all location data requests. Of course the concern for privacy in all of its
dimensions was central to the Framers’ contemplation. But the Fourth Amendment, to state
the obvious, calls also for a balance between individual privacy and public safety. Favoring
one over the other is at odds with the textual “touchstone” of the Amendment, which is
reasonableness. See Maryland v. King, 569 U.S. 435, 448 (2013). Respecting Fourth
Amendment balance means protecting “that degree of privacy against government that

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existed when the Fourth Amendment was adopted.” Carpenter v. United States, 585 U.S.
296, 305 (2018). Not less, of course. But also not more.
So yes, the Bill of Rights stands vigilant guard against the abuses of the state. The
Fourth Amendment is itself a prime illustration of its function. Yet privacy is also
threatened by, say, a theft of personal items. And privacy is in part a peace of mind. The
prospect of criminal malefactors intruding on that peace can only mean our privacy has
been compromised. That the transgression is attributable to private actors does not mean it
cannot be part of the calculus of reasonableness which, again, is our Fourth Amendment
touchstone. Seen in this light, privacy is not invariably in an adversarial relationship with
the state, but something the state can take measured steps to protect and provide.
II.
Even if there was a search, there is no room for emergent judicial hostility toward
this new investigative tool. Disabling the government from using geofence location data
would spurn the basic Fourth Amendment balance and undermine legitimate law
enforcement in at least three basic ways.
One, this restraint on investigative tools would frustrate law enforcement’s ability
to keep pace with tech-savvy criminals. Lawless actors of all kinds are growing more
sophisticated and leveraging new technologies to commit crimes and evade detection.
Transnational criminal organizations rely on digital currencies and encrypted
communications to conceal their violence and fraud. 2023 W HITE H OUSE STRATEGY TO
COMBAT T RANSNATIONAL O RGANIZED CRIME 3–4, 21 (2023). Terrorists likewise deploy
emerging technologies like encryption, biotechnology, and artificial intelligence. Ian Moss,

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U.S. Dep’t of State, Opening Remarks on Addressing Emerging Technology in the Realm
of Racially or Ethnically Motivated Violent Extremism (Feb. 14, 2024). Even small-time
pimps encrypt their devices to block lawful access to their databases of sex-trafficking
victims. See Lawful Access, Office of Legal Policy, U.S. Dep’t of Justice (Nov. 18, 2022).
Examples abound. In this age of innovation, those who would break the law spare no
expense to employ the latest and greatest technological tools.
All the while, under appellant’s view, local, state, and federal officers would lose
the tools they need to protect the public from the modern-day criminal. More cold cases
would go unsolved. Think of a murder where the culprit leaves behind his encrypted phone
and nothing else. No fingerprints, no witnesses, no murder weapon. But because the killer
allowed Google to track his location, a geofence warrant can crack the case. See Damien
Christopher & Nick Penzenstadler, Cold Cases Cracked by Cellphones: How Police Are
Using Geofence Warrants to Solve Crimes, USA TODAY (Sept. 8, 2022). Taking this tool
of last resort out of law enforcement’s hands would leave these case files collecting dust.
The Fourth Amendment does not require allowing criminals to take advantage of cutting-
edge technologies while preventing the government from doing the same. Technology
enables the lawbreaker. Courts disable the government. This imbalance will only grow with
time.
Two, law enforcement under appellant’s view would be robbed of valuable channels
of communication with the private sector. This case is a good example of those channels
at work. Chatrie, like one-third of Google users, signed up for a program that shared his
location data with Google. In return he got a “virtual journal of his past travels” and “real-

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time traffic updates.” United States v. Chatrie, 107 F.4th 319, 322 (4th Cir. 2024), panel
opinion vacated by order of the en banc court (Nov. 1, 2024). And because he brought his
phone to the robbery, the government was able to place Chatrie at the crime scene with
Google’s help.
Chatrie would shut down this kind of sensible public-private cooperation. Doing so
would override the equilibrium between user privacy and public safety that has emerged
organically, without judicial intervention, from an ecosystem of customers, companies, and
law enforcement. Critics seem to presuppose that private companies such as Google are
naturally disposed to compromise the privacy of their users. Quite the contrary. Google has
every incentive to protect the privacy of those who utilize its services. Not to do so risks
damaging its business.
The procedures used by Google here prove the point. In responding to the
government’s location data request, Google insisted on a rigorous “three-step process” to
protect user privacy. Chatrie, 107 F.4th at 324. It kept all data anonymized until officers
were able to zero in on a small group of suspects. Only then did Google disclose the
identities of Chatrie and two others. Far from a “digital dragnet,” the process used here
reflected the reasonable balance between privacy and safety that the Fourth Amendment
envisioned. By urging us to rule broadly that geofence warrants are impermissible, Chatrie
would unleash a fear of legal liability that would chill data sharing between public and
private sectors and foreclose fruitful communication over the respective values of personal
privacy and effective law enforcement.

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Three, some of my colleagues go down a dangerous road by casting the use of
geofence data as some new monster. True, the technology is new, but the technique is a
familiar one. In fact the technique is not too different from the traditional winnowing
methods that criminal investigators have always used. Investigations often start out broad.
Culprits are not always known, crime scenes may be crowded, and detectives have to start
somewhere. They canvass the surroundings, review security footage, and pick out and rule
out persons of interest. Analysis of geofence data follows this same narrowing progression.
So too do keyword searches and tower dumps. Will courts put a stop to those too? See Orin
Kerr, The Fifth Circuit Shuts Down Geofence Warrants—And Maybe a Lot More,
L AWFARE (Aug. 14, 2024). Will courts seek to disable law enforcement in cases where
there are no eyewitnesses and few forensic clues? If so, they are far ahead of the Supreme
Court in Carpenter, which ruled on seven days’ worth of location data, not the snapshot
before us now.
III.
There is a further difficulty with categorically invalidating geofence warrants,
namely that of extending the exclusionary rule with no regard to its costs. In Hudson v.
Michigan, 547 U.S. 586 (2006), the Supreme Court cautioned against the rule’s
“indiscriminate application” and reiterated that it should apply only when the “deterrence
benefits” outweigh the “social costs.” Id. at 591. The social costs here are significant. As
we have explained, geofence location data is often the only way to identify and convict
perpetrators like Chatrie. Excluding this evidence from trial gives these criminals, in the
words of the Supreme Court, “a get-out-of-jail-free card.” Id. at 595. A reflexive expansion

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of the exclusionary rule ignores the primary allegiance of courts to probative evidence and
neglects the Supreme Court’s clear instructions in Hudson.
The creation of remedies involves the weighing of costs and benefits, which often
falls within the domain of legislators. Indeed, legislatures routinely enact laws balancing
the competing considerations of personal privacy and public safety. For instance, the
Electronic Communications Privacy Act, Pub. L. No. 99–508, 100 Stat. 1848 (1986),
authorizes the government to collect people’s communications and digital data for law
enforcement purposes. But the law offers a range of procedural safeguards—anything from
an administrative subpoena to a court-issued warrant based on probable cause—and
remedies depending on the nature of the data. This type of compromise is a classic
legislative task. Applying the exclusionary rule categorically to geofence warrants
preempts legislative input in an area whose real impact upon the body politic would seem
to invite some measure of popular participation.
IV.
As we contemplate the future, Fourth Amendment interpretation leads to twin risks.
One is the risk that privacy will succumb to the evermore invasive technological
capabilities at the hands of an evermore intrusive state. The other risk, which is just as real,
is that of privileging those who break the law over those who would enforce it. Either future
portends stark consequences for society where individual dignity cannot in the end be
divorced from an intuitive sense of personal safety.
The facts of this case are illustrative. Chatrie terrorized the employees and patrons
of the Call Federal Credit Union in Midlothian, Virginia. He walked into the bank armed

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with a handgun, told the teller that he had accomplices outside and that he was holding her
family hostage, and threatened to “hurt[] everyone in sight” if she called the cops. United
States v. Chatrie, 590 F. Supp. 3d 901, 905–06 (E.D. Va. 2022). Brandishing his gun, he
forced everyone to the ground and ordered the manager to empty the safe. Chatrie was able
to escape with $195,000. Because he was not apprehended at the scene, he eluded law
enforcement for months. Officers were out of traditional leads. Only the geofence warrant
eventually allowed police to track Chatrie down and restore a sense of resolution to the
community. Without geofence location data, crimes even more serious than this one will
escape detection.
The sheer breadth of appellant’s position is disquieting. Those who support it seek
a broad judicial declaration that geofence warrants would be unconstitutional in all their
forms, no matter how specific and particularized. The geofence warrant here was closely
confined to a particular time, place, and incident. There can be abuses to be sure, but courts
can review the temporal and spatial character of these warrants as we would any Fourth
Amendment claim. To strike the warrant down here comes pretty nearly to invalidating it
everywhere. No matter says appellant. All such warrants are on the chopping block.
Crime invades privacy. Crime limits freedom and narrows space. The fact that the
Fourth Amendment exists to check the undeniable excesses of the modern state does
nothing to diminish the fact that crime imperils the very values the Fourth Amendment
exists to protect. The Framers resolved this dilemma by making reasonableness the
Amendment’s touchstone. It is dispiriting that some would proceed with nary a thought

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given to that two-sided balance which reasonableness above all denotes. It will never do to
see the future with but a single eye.

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NIEMEYER, Circuit Judge, concurring:
I am pleased to join the opinions of Judge Wilkinson and Judge Richardson in full.
Today’s Fourth Amendment caselaw often starts with a pre-Internet analogy. See
Carpenter v. United States, 585 U.S. 296, 306 (2018). I write separately because I believe
that a commonsense analogy dictates the same result reached by the opinions of Judge
Wilkinson and Judge Richardson.
To begin, the Fourth Amendment protects the people “in their persons, houses,
papers, and effects” against unreasonable searches. U.S. Const. amend. IV. It has also
been construed to extend beyond those textual objects to protect certain expectations of
privacy. See Katz v. United States, 389 U.S. 347, 353 (1967); id. at 361 (Harlan, J.,
concurring). And recently, the Supreme Court held in Carpenter that the Fourth
Amendment protects a person’s expectation of privacy in “the whole of his physical
movements.” 585 U.S. at 313. Thus, when law enforcement, without a warrant, accesses
a person’s continuously collected and automatically generated cell-site location
information, it violates that expectation of privacy. See id. at 315–16. But Carpenter left
in place many existing limits on the scope of the Fourth Amendment. Apart from
protecting the unique data-collection system at issue there, the Carpenter Court explained
that it was not “disturb[ing] the application” of the third-party doctrine “or call[ing] into
question conventional surveillance techniques and tools, such as security cameras. Nor
[did it] address other business records that might incidentally reveal location information.”
Id. at 316.

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One of the “conventional surveillance techniques” that Carpenter left untouched is
law enforcement’s practice of collecting and following “markers,” or clues, voluntarily left
behind and abandoned by a person at the scene of a crime or in connection with the crime.
These markers can reveal who committed the crime, and, when the crime was committed
in a public place or in the place of a third person, they may be collected by law enforcement
without a warrant. Thus, law enforcement is entitled to retrieve boot prints, tire tracks,
shell casings, a scarf or a cap, and items left with fingerprints or DNA on them. Similarly,
they can retrieve third-person records of a suspect’s presence, such as pictures and videos
taken routinely at the scene, records of tolls paid, or records of credit card transactions.
Indeed, such third-party records might include a note left with a teller during a bank
robbery. Collecting markers such as these from public places or third persons is the stuff
of law enforcement, enabling it to solve crimes and prosecute suspects, and the person who
left them behind is not “searched” in his person and effects, in violation of the Fourth
Amendment.
Of course, if a person were careful not to leave footprints, fingerprints, shell casings,
or other markers behind, law enforcement would have to turn to other techniques and
strategies to advance its investigation. But when such markers are left behind, law
enforcement should not be denied the benefit of the person’s carelessness when solving a
crime. And Carpenter says nothing to the contrary. What Carpenter does say is that law
enforcement needs to obtain a warrant before it utilizes digital technology to track a
citizen’s long-term movements — “the whole of his physical movements” — at least when
that person is, in effect, compelled to leave behind a digital footprint wherever he goes.

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585 U.S. at 313, 315; see also United States v. Jones, 565 U.S. 400, 430 (2012) (Alito, J.,
concurring in the judgment); Leaders of a Beautiful Struggle v. Balt. Police Dep’t, 2 F.4th
330, 341 (4th Cir. 2021) (en banc). But those features are not present here, and, as this
case is otherwise well-removed from the text of the Fourth Amendment, I would hold that
law enforcement did not conduct a search.
This case relates to law enforcement’s effort to collect markers from third persons
voluntarily left behind by a person during the commission of a crime. In this case, the
person left behind electronic location data that he voluntarily transmitted from the scene of
the crime by his cell phone. Law enforcement did not collect the data from the person or
the person’s cell phone, which would require a warrant, see Riley v. California, 573 U.S.
373, 401 (2014), but from a third person who received the person’s voluntarily transmitted
data and stored them in a data bank, see Smith v. Maryland, 442 U.S. 735, 743–44 (1979);
United States v. Miller, 425 U.S. 435, 443 (1976). In this sense, the data, when limited to
the time and place of the crime, were no different than any other marker left behind by a
perpetrator.
What might distinguish such electronic data from other markers is the scope of the
data collection. Here, the data were retained by the third person in a large data bank —
Google’s Sensorvault — which includes information unrelated to the time and place of the
crime. The broad scope of that data bank could raise privacy concerns for those whose
data were stored there, including the suspect’s data that did not constitute a marker from
the crime scene. But law enforcement accessed only two hours’ worth of location data,
which is far from “the whole of [anyone’s] physical movements.” Carpenter, 585 U.S. at

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313. And law enforcement relied on procedures designed to isolate the data constituting
markers left behind at the crime scene from other, unrelated data, which helped mitigate
any privacy concerns.
The geofence warrant issued in this case initially required Google to produce data
transmitted by cell phones only (1) from the scene of the crime and (2) during the time
when the crime was committed. They were thus potential crime markers, which helped
law enforcement solve the crime and were not materially distinct from the fingerprints or
shell casings left behind by a prior era’s less-than-careful perpetrators.
At bottom, this case is a good example of law enforcement properly balancing its
need to solve and prosecute crimes with citizens’ privacy concerns under the Fourth
Amendment. Neither the suspect nor any other person whose data was stored in the data
bank could legitimately claim, in view of the procedures followed, that his rights were
violated. Judge Richardson’s opinion neatly, systematically, and accurately sets forth the
legal principles supporting this conclusion, and Judge Wilkinson’s opinion elegantly
articulates the public policies that this conclusion promotes.
In addition, I also concur in the judgment of the court holding that, in any event, law
enforcement’s collection of the data from Google was protected because law enforcement
relied in good faith on a warrant issued by a detached and neutral judicial officer. See
United States v. Leon, 468 U.S. 897, 922–23 (1984).

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KING, Circuit Judge, concurring:
I am pleased to join in the fine concurring opinions of Judge Wilkinson and Judge
Richardson. In addition, I agree that the officers acted in good faith, and I therefore also
support the affirmance of the district court’s judgment on that basis.

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WYNN, Circuit Judge, with whom Judges THACKER, HARRIS, BENJAMIN, and
BERNER join, and with whom Judge GREGORY joins except as to footnote 1, concurring
in the judgment:
The surveillance technologies at issue in this case—the very same ones that seem to
thrill my colleagues who join Judge Wilkinson’s separate opinion—would have been
unimaginable to the Founders. Yet, in Carpenter v. United States, 585 U.S. 296 (2018),
our Supreme Court rightly recognized that the principles enshrined in the Fourth
Amendment do not wither in the face of advancing technologies. Rather, they must be
vigorously protected from ever-expanding methods of government intrusion.
The Court in Carpenter reaffirmed a fundamental truth: until, and unless, the
Constitution is amended, it is the duty of the judiciary to defend constitutional rights against
encroachments that the Framers could not have foreseen but surely would have found
intolerable.
Thus, “when a Fourth Amendment case presents a novel question of law whose
resolution is necessary to guide future action by law enforcement officers and magistrates,
there is sufficient reason for [a court] to decide the violation issue before turning to the
good-faith question.” United States v. Bosyk, 933 F.3d 319, 332 n.10 (4th Cir. 2019)
(quoting Illinois v. Gates, 462 U.S. 213, 264 (1983) (White, J., concurring)); see United
States v. Leon, 468 U.S. 897, 925 (1984). “As demonstrated by the divergent decisions of
district courts”—and here, of circuit courts—“this is one such case.” Bosyk, 933 F.3d at
332 n.10.
The constitutional question in this case has been fully briefed, argued and
exhaustively debated—not only by the parties but by amici and members of this Court.

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And it is unclear what future case could better tee up the issue. Judicial modesty does not
demand judicial abdication.
Yet, by declining to reach the merits in this matter, this Court squanders a critical
opportunity to clarify the Fourth Amendment’s application to emerging surveillance
technologies. Instead, we take shelter in the judge-made doctrine of “good faith,” leaving
both courts and citizens to grope in the dark as to the limits of governmental power in the
digital age. The result? Individuals subject to sweeping, sophisticated surveillance with
little or no judicial oversight—an outcome wholly at odds with our constitutional design.
I therefore write separately to explain why, in obtaining Google Location History
data traceable to Okello Chatrie, the police conducted a Fourth Amendment search.1
I.
The Fourth Amendment promises “secur[ity] . . . against unreasonable searches and
seizures.” U.S. Const. amend. IV. Surveillance technologies, though also deployed in the
name of security, pose a dynamic and resilient threat to that right. Technology continually
advances; consequently, maintaining the balance between individual privacy and public
safety requires vigilance. Recognizing this, the Supreme Court has allowed Fourth
Amendment jurisprudence to evolve alongside technology. I begin by surveying that
evolution, with particular attention to its latest chapter: the Court’s decision in Carpenter.
1 Although I believe that this case involved a Fourth Amendment search—and that
we should say so—I acknowledge that the conditions for application of the good-faith
exception to the exclusionary rule are met here.

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A.
Early Supreme Court decisions made clear that a government agent’s physical
trespass into a private space is a search, and thus requires a warrant. But as the
Government’s capacity to surveil at a distance expanded, so did the Fourth Amendment’s
protections. See Carpenter, 585 U.S. at 304. The modern rule—adapted from Justice
Harlan’s concurring opinion in Katz v. United States, 389 U.S. 347 (1967), and reaffirmed
many times since—is that “[w]hen an individual seeks to preserve something as private,
and his expectation of privacy is one that society is prepared to recognize as
reasonable, . . . official intrusion into that private sphere generally qualifies as a search and
requires a warrant supported by probable cause.” Carpenter, 585 U.S. at 304 (internal
quotation marks omitted).
In the 1970s and 1980s—before the internet age—the Supreme Court placed two
key limitations on Katz’s expansion of recognized Fourth Amendment protections: the
third-party and public-surveillance doctrines. See id. at 306–09. Understanding those
limitations is essential to understanding the Court’s later decision in Carpenter.
First, the third-party doctrine stems from decisions issued over 45 years ago: Smith
v. Maryland, 442 U.S. 735 (1979), and United States v. Miller, 425 U.S. 435 (1976).
In Smith, police used a pen-register device to collect phone numbers the suspect
dialed on his home phone. Smith, 442 U.S. at 737. And in Miller, police accessed the
suspect’s bank records, such as checks and deposit slips. Miller, 425 U.S. at 437–38. The
Supreme Court held that the suspects had no reasonable expectation of privacy in those
relatively unrevealing records, which the suspects had voluntarily exposed to third parties

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in the ordinary course of business. See Smith, 442 U.S. at 737, 741–42; Miller, 425 U.S. at
440–43; Carpenter, 585 U.S. at 308–09 (discussing Smith and Miller).
Second, the public-surveillance doctrine emerges from decisions issued over 40
years ago, and centers on differing expectations of privacy in public versus private spaces.
In United States v. Knotts, 460 U.S. 276 (1983), the Court held that police did not
conduct a Fourth Amendment search when they used a “beeper”—that is, “a radio
transmitter” that “emits periodic signals that can be picked up by a radio receiver”—to
keep a vehicle in view during a single drive “on public thoroughfares.” Id. at 277, 281. The
Court reasoned that police could have tracked the vehicle’s movements without the
beeper—by physically following it—so the suspect had no reasonable expectation of
privacy in those movements. Id. at 281–82, 285.
Knotts “was careful to distinguish between the rudimentary tracking facilitated by
the beeper and more sweeping modes of surveillance.” Carpenter, 585 U.S. at 306. The
Court stressed that the beeper merely “augment[ed]” the officers’ own “sensory faculties.”
Knotts, 460 U.S. at 282. And it cautioned that, should “twenty-four hour surveillance of
any citizen” become “possible,” “different constitutional principles may be applicable.”
Carpenter, 585 U.S. at 306–07 (quoting Knotts, 460 U.S. at 283–84).
The Court distinguished Knotts in United States v. Karo, 468 U.S. 705 (1984),
which held that police conducted a Fourth Amendment search when they used a beeper to
track a container as it moved between commercial lockers and private residences. Id. at
708–10, 714–18. The Court explained that because “private residences are places in which
the individual normally expects privacy free of governmental intrusion not authorized by

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a warrant, and that expectation is plainly one that society is prepared to recognize as
justifiable,” “[s]earches and seizures inside a home without a warrant are presumptively
unreasonable absent exigent circumstances.” Id. at 714–15. Although tracking the beeper’s
location was “less intrusive than a full-scale search,” it “reveal[ed] a critical fact about the
interior of the premises”; and unlike the public movements of the vehicle in Knotts, police
“could not have otherwise obtained [that information] without a warrant.” Id. at 715.
In short, Smith, Miller, Knotts, and Karo—all decided before 1985—recognized that
there is no reasonable expectation of privacy in simple records voluntarily conveyed to
third parties in the ordinary course of business, or in one’s short-term public movements.
But as new surveillance technologies “enhanced the Government’s capacity to encroach
upon areas normally guarded from inquisitive eyes,” the Supreme Court “sought to ‘assure
[ ] preservation of that degree of privacy against government that existed when the Fourth
Amendment was adopted.’” Carpenter, 585 U.S. at 305 (quoting Kyllo v. United States,
533 U.S. 27, 34 (2001)). Three cases illustrate that endeavor.
First, Kyllo v. United States held that police use of a thermal-imaging device to
monitor heat waves emanating from inside a home was a search. Kyllo, 533 U.S. at 34–35.
The Court explained that even though the device was operated from a public street outside
the home, it allowed police to “explore details of the home that would previously have been
unknowable without physical intrusion.” Id. at 40. “Because any other conclusion would
leave homeowners ‘at the mercy of advancing technology,’” the Court “determined that
the Government—absent a warrant—could not capitalize on such new sense-enhancing

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technology to explore what was happening within the home.” Carpenter, 585 U.S. at 305
(quoting Kyllo, 533 U.S. at 35).
Next, in United States v. Jones, 565 U.S. 400 (2012), the Court grappled with “more
sophisticated surveillance of the sort envisioned in Knotts and found that different
principles did indeed apply.” Carpenter, 585 U.S. at 307. Jones held that the police’s
installation and use of a GPS tracking device to monitor the location of a suspect’s vehicle
for 28 days constituted a search. Jones, 565 U.S. at 403–04. Although Justice Scalia’s
opinion for the five-justice majority rested only on traditional trespass principles, five other
justices authored or joined concurrences concluding that the GPS monitoring was a search
under Katz’s reasonable-expectation-of-privacy test—even though the intrusion only
captured public movements. See id. at 413–18 (Sotomayor, J., concurring); id. at 418–31
(Alito, J., concurring in the judgment). The concurring justices noted that, as compared to
the one-trip beeper tracking in Knotts, the GPS tracking in Jones was both longer and more
precise. See id. at 415 (Sotomayor, J., concurring); id. at 429–30 (Alito, J., concurring in
the judgment).
Specifically, four concurring justices emphasized that long-term GPS tracking
violated reasonable expectations of privacy because it enabled police to tail a suspect for
much longer than would have been possible using traditional investigative methods. See
id. at 429 (Alito, J., concurring in the judgment) (“In the pre-computer age, the greatest
protections of privacy were neither constitutional nor statutory, but practical.”).
For the fifth concurring justice, Justice Sotomayor, even short-term GPS tracking
violated reasonable expectations of privacy because it enabled such precise surveillance.

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Id. at 415 (Sotomayor, J., concurring). She reasoned that GPS technology “generates a
precise, comprehensive record of a person’s public movements that reflects a wealth of
detail about her familial, political, professional, religious, and sexual associations.” Id. And
because a short GPS search is cheaper, easier to use, and more concealable than
conventional methods of surveillance, “it evades the ordinary checks that constrain abusive
law enforcement practices: ‘limited police resources and community hostility.’” Id. at 416
(quoting Illinois v. Lidster, 540 U.S. 419, 426 (2004)). Moreover, GPS technology permits
the Government to “store” and “efficiently mine” records of an individual’s movements
for “years into the future.” Id. at 415. For these reasons, even a short GPS search could
chill First Amendment freedoms and “alter the relationship between citizen and
government in a way that is inimical to democratic society.” Id. at 416 (citation omitted).2
Two years later, the Court held in Riley v. California, 573 U.S. 373 (2014), that
police must obtain a warrant to look through the contents of an arrestee’s cell phone during
an arrest, even though police may generally conduct brief searches of an arrestee’s person
without a warrant. Id. at 385–86. The Court recognized that digital storage compiles
personal information of unprecedented volume, variety, and retrospectivity into a single
2 “More fundamentally,” Justice Sotomayor argued, “it may be necessary to
reconsider the premise that an individual has no reasonable expectation of privacy in
information voluntarily disclosed to third parties.” Jones, 565 U.S. at 417. That “approach
is ill suited to the digital age, in which people reveal a great deal of information about
themselves to third parties in the course of carrying out mundane tasks,” without expecting
their devices “to enable covert surveillance of their movements.” Id. at 417 & n.*.

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device (or, in the Fourth Amendment’s language, “effect”)—and consequently, that
protecting privacy rights in such effects require a different approach. Id. at 393–97.
In each of these seminal cases, the Supreme Court grappled with how to protect
constitutional privacy rights from encroaching technologies. And, in the majority opinions
in most of these cases and in the Jones concurrences, the Court recognized that then-
existing Fourth Amendment case law was ill-adapted to the realities of modern technology.
B.
The Court’s growing recognition of the profound impact of technological
advancements on Fourth Amendment rights was on full display in its 2018 decision in
Carpenter v. United States. While building on all that came before it, Carpenter marked a
“sea change” in Fourth Amendment jurisprudence as it pertains to “a person’s digital
information.” Matthew Tokson, The Aftermath of Carpenter: An Empirical Study of Fourth
Amendment Law, 2018–2021, 135 Harv. L. Rev. 1790, 1799–1800 (2022) (capitalization
standardized).
In Carpenter, the Court held that law enforcement’s request for seven days of the
defendant’s historical cell-site location information (“CSLI”) from his wireless carrier,
which produced two days’ worth of data, was a search. Carpenter, 585 U.S. at 302, 316.
CSLI records are created when cell phones connect to nearby cell towers, which, in
Carpenter, occurred at the start and end of the defendant’s incoming and outgoing calls.
Id. at 302. The cell-site records were maintained by wireless carriers, which raised the
possibility that the third-party doctrine would apply. And indeed, below, the Sixth Circuit
had “held that [the defendant] lacked a reasonable expectation of privacy in the location

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information collected by the FBI because he had shared that information with his wireless
carriers.” Id. at 303; see United States v. Carpenter, 819 F.3d 880, 888 (6th Cir. 2016). In
other words, the Sixth Circuit took a view very similar to that of some of my colleagues
here. See Judge Richardson Concurring Op., infra, Part II.B.
But the Supreme Court reversed. In so doing, it acknowledged that the third-party
doctrine is an increasingly tenuous barometer for reasonable privacy expectations in the
digital era. Instead, the Court laid the foundation for a new, multifactor test to determine
when government surveillance using digital technologies constitutes a search.
Carpenter began with the Katz test: the Fourth Amendment protects against
intrusion into the sphere in which an individual has a reasonable expectation of privacy.
Carpenter, 585 U.S. at 304. It then explained that, while “no single rubric” defines
reasonable expectations of privacy, the Court’s analysis must always be “informed by
historical understandings of what was deemed an unreasonable search when the Fourth
Amendment was adopted.” Id. at 304–05 (cleaned up). These historical understandings,
according to the Court, have a few “guideposts”: “the [Fourth] Amendment seeks to secure
the privacies of life against arbitrary power,” “to place obstacles in the way of a too
permeating police surveillance,” and, most importantly, to “assure preservation of that
degree of privacy against government that existed when the Fourth Amendment was
adopted.” Id. at 305 (cleaned up). The Court emphasized that in cases like Kyllo and Riley,
it kept those “Founding-era understandings in mind” when considering “innovations in
surveillance tools.” Id.

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Against that background, the Court quickly concluded that CSLI—“personal
location information maintained by a third party”—“does not fit neatly” into any existing
line of Fourth Amendment jurisprudence. Id. at 306. The third-party-disclosure and public-
surveillance cases could “inform [the Court’s] understanding of the privacy interests at
stake,” but neither squarely applied. Id. In fact, the Court expressly “decline[d] to extend”
the third-party doctrine to CSLI—even though CSLI data is maintained by third-party
companies—because CSLI records are a “qualitatively different category” of information
from the phone numbers and bank records at issue in its third-party cases. Id. at 309. “After
all,” the Court observed, “when Smith was decided in 1979, few could have imagined a
society in which a phone goes wherever its owner goes, conveying to the wireless carrier
not just dialed digits, but a detailed and comprehensive record of the person’s movements.”
Id. at 309.
Instead of “mechanically applying the third-party doctrine,” id. at 314, Carpenter
applied a new framework rooted in historical understandings of Fourth Amendment
privacy rights but adapted to the particular surveillance technology at issue. Specifically,
the Court identified four aspects of CSLI surveillance that made it “qualitatively different”
from older techniques—its comprehensiveness, its capacity for retrospective tracking, the
intimacy of the information it reveals, and its ease of access for police.3 See id. at 309–13.
3 Carpenter’s framework drew on the reasoning of the Jones concurrences, and
particularly Justice Sotomayor’s concurrence. Cf. Jones, 565 U.S. at 415–16 (Sotomayor,
J., concurring) (observing that “GPS monitoring generates a precise, comprehensive
record” of “intimate information” that can be “store[d]” and “efficiently mine[d] . . . for
information years into the future”).

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Based on those four considerations, the Court concluded that police access to CSLI violates
reasonable expectations of privacy. Id. at 313.
Then, in a separate section of the opinion, the Court further distinguished Smith and
Miller by explaining that the conveyance of CSLI is also not meaningfully voluntary. Id.
at 313–16. The opinion’s concluding paragraph reads, in part: “In light of the deeply
revealing nature of CSLI, its depth, breadth, and comprehensive reach, and the inescapable
and automatic nature of its collection, the fact that such information is gathered by a third
party does not make it any less deserving of Fourth Amendment protection.” Id. at 320.
II.
Carpenter established a multifactor approach to assessing reasonable expectations
of privacy in digital information.4 An application of the Carpenter factors in this case
4 Leading scholars agree, though they differ as to which factors are mandatory or
most important. See, e.g., Paul Ohm, The Many Revolutions of Carpenter, 32 Harv. J.L. &
Tech. 357, 363, 369 (2019) (recognizing that Carpenter created “new, multi-factor test” to
analyze an individual’s reasonable privacy expectation against intruding technology and
“herald[ed] a new mode of Constitutional analysis”); Susan Freiwald & Stephen W. Smith,
The Carpenter Chronicle: A Near-Perfect Surveillance, 132 Harv. L. Rev. 205, 219 (2018)
(multifactor analysis was “clearly central” to the Court’s holding); Tokson, The Aftermath
of Carpenter, supra, at 1830 (describing the “Carpenter factors” and concluding from a
survey of cases that “[a] multifactor Carpenter test has begun to emerge from the lower
court[s]”); Sherwin Nam, Bend and Snap: Adding Flexibility to the Carpenter Inquiry, 54
Colum. J.L. & Soc. Probs. 131, 132 (2020) (stating that Carpenter “broke new ground in
the constitutional right to privacy in electronic data” and employed a “five-factor” test);
Helen Winters, An (Un)reasonable Expectation of Privacy? Analysis of the Fourth
Amendment When Applied to Keyword Search Warrants, 107 Minn. L. Rev. 1369, 1381,
1390 (2023) (Carpenter “marked a new period of Fourth Amendment jurisprudence” and
laid out “several factors relevant to its decision”); Antony Barone Kolenc, “23 and Plea”:
Limiting Police Use of Genealogy Sites After Carpenter v. United States, 122 W. Va. L.
Rev. 53, 71–72 (2019) (concluding that Carpenter “alter[ed] Fourth Amendment law” by
recognizing a privacy interest in the “whole of a person’s physical movements,” and

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compels the conclusion that Okello Chatrie had a reasonable expectation of privacy in his
Location History data. 5
A.
Carpenter first considered the comprehensiveness of CSLI data, observing that it
“tracks nearly exactly the movements of [a cell phone’s] owner,” providing “an all-
encompassing record of the holder’s whereabouts.” Carpenter, 585 U.S. at 311. Unlike a
vehicle, “a cell phone—almost a ‘feature of human anatomy’— . . . faithfully follows its
owner beyond public thoroughfares and into private residences, doctor’s offices, political
headquarters, and other potentially revealing locales.” Id. (quoting Riley, 573 U.S. at 385).
Like CSLI, Location History tracks a smartphone’s location—only more precisely.
CSLI (as described in Carpenter) places a user within a “wedge-shaped sector,” id. at 312,
ranging from “a dozen” to “several hundred” city blocks in size, which can be “up to 40
“balanced five factors” to analyze that interest); Matthew Tokson, The Carpenter Test as a
Transformation of Fourth Amendment Law, 2023 U. Illinois L. Rev. 507, 517–20 (2023)
(outlining a three-factor test); Allie Schiele, Learning from Leaders: Using Carpenter to
Prohibit Law Enforcement Use of Mass Aerial Surveillance, 91 Geo. Wash. L. Rev.
Arguendo 14, 17–18 (2023) (pointing out “Carpenter’s focus on five central factors”);
Nicole Mo, If Wheels Could Talk: Fourth Amendment Protections Against Police Access
to Automobile Data, 98 N.Y.U. L. Rev. 2232, 2251 (2023) (recognizing factors); Luiza M.
Leão, A Unified Theory of Knowing Exposure: Reconciling Katz and Carpenter, 97 N.Y.U.
L. Rev. 1669, 1684 (2022) (same); Matthew E. Cavanaugh, Somebody’s Tracking Me:
Applying Use Restrictions to Facial Recognition Tracking, 105 Minn. L. Rev. 2443, 2468
(2021) (same).
5 Police obtained Chatrie’s Location History data when they obtained Location
History data that was traceable to him. Here—as Judge Berner persuasively explains—that
happened at Step 2 of Google’s three-step process. See Judge Berner Concurring Op., infra,
Part II.B.i.

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times more imprecise” in rural areas, id. at 324 (Kennedy, J., dissenting). But Location
History can locate a user within meters—and can even measure elevation, identifying the
specific floor in a building where a person might be. United States v. Chatrie, 590 F. Supp.
3d 901, 908–09 (E.D. Va. 2022). Moreover, the CSLI collected in Carpenter was only
recorded when a user placed or received a call—no call, no data. Carpenter, 585 U.S. at
302. But Location History tracks a user’s location automatically, every two minutes.
Chatrie, 590 F. Supp. 3d at 908. In Carpenter, law enforcement collected only about 101
CSLI data points in a full day. Carpenter, 585 U.S. at 302. Here, police were able to collect
an average of about 76 Location History data points on each person surveilled in just two
hours. See J.A. 1121 (explaining that “Google produced . . . a total of 680 data points” for
“nine accounts” at Step 2). If CSLI as described in Carpenter enables “near perfect
surveillance,” Carpenter, 585 U.S. at 312, so too does Location History.
B.
Carpenter next considered “the retrospective quality of [CSLI] data,” which (at the
time) was “continually logged for all of the 400 million devices in the United States” and
retained by wireless carriers “for up to five years.” Carpenter, 585 U.S. at 312. CSLI
allowed police to “travel back in time” to “reconstruct a person’s movements,” unlocking
“a category of information otherwise unknowable.” Id. And because CSLI tracking “runs
against everyone,” “police need not even know in advance whether they want to follow a
particular individual, or when.” Id. “Whoever the suspect turns out to be, he has effectively
been tailed every moment of every day for five years.” Id.

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Location History data raises similar concerns. Google begins collecting Location
History the moment the feature is enabled and retains it indefinitely, enabling police to
retrospectively tail a suspect with remarkable precision.6 And like CSLI, police need not
identify the suspect in advance—Location History data is available for “numerous tens of
millions” of Google users. Chatrie, 590 F. Supp. 3d at 907. Of course, a geofence limits
the size and duration of any particular law enforcement data-grab. But Carpenter’s
retrospectivity analysis emphasized the vast scope of available CSLI data, which gives
police “access to a category of information otherwise unknowable.” Carpenter, 585 U.S.
at 312 (emphasis added). So too here.
In fact, Location History permits even broader surveillance than CSLI. Collecting
CSLI data at least requires police to produce a suspect’s phone number in order to access
a five-year trove of their location data. But a geofence can uncover the Location History of
an unlimited number of individuals, none of whom were previously identified or suspected
of any wrongdoing. Indeed, the very point of a geofence is to generate leads where none
exist.7 Consequently, Carpenter’s concerns about retrospective surveillance apply to
Location History with even greater force.
6 This discussion reflects the record in this case, not Google’s current or future
practices.
7 This feature of geofence warrants makes them uncomfortably akin to the “reviled”
general warrants that the Framers intended the Fourth Amendment to forbid. Carpenter,
585 U.S. at 303 (quoting Riley, 573 U.S. at 403); see United States v. Smith, 110 F.4th 817,
836–38 (5th Cir. 2024). “The general warrant specified only an offense . . . and left to the
discretion of the executing officials the decision as to which persons should be arrested and
which places should be searched.” Steagald v. United States, 451 U.S. 204, 220 (1981). As

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C.
Carpenter further concluded that “time-stamped [location] data provides an
intimate window into a person’s life, revealing not only his particular movements, but
through them his ‘familial, political, professional, religious, and sexual associations.’”
Carpenter, 585 U.S. at 311 (quoting Jones, 565 U.S. at 415 (Sotomayor, J., concurring)).
Such “location records,” the Court recognized, “hold for many Americans the privacies of
life.” Id. (quoting Riley, 573 U.S. at 403).
The same is true of Location History. The two hours of geographically unbounded
data requested by police at Step 2 illustrate that “the potential intrusiveness of even a
snapshot of precise location data should not be understated.” United States v. Smith, 110
F.4th 817, 833 (5th Cir. 2024). The geofence in this case centered on “a busy part of the
Richmond metro area” between 3:50 and 5:50 p.m., when many people are leaving work
or school—and of course, it had no geographic boundaries at Step 2. Chatrie, 590 F. Supp.
3d at 925; see id. at 919. Two hours of Location History for accounts passing through that
geofence could enable police to tour a person’s home, capture their romantic rendezvous,
or accompany them to church.
This case presents textbook examples of how police access to this digital
information can invade the privacies of innocent users. At the suppression hearing,
Judge Berner explains, probable cause may support a tightly limited geofence warrant. See
Judge Berner Concurring Op., infra, Part II.D. But if accessing Location History is not a
search at all, police would not even need to specify an offense before dipping into years of
personal location data on millions of Americans.

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Chatrie’s counsel demonstrated that the anonymized Step 2 data produced in response to
this geofence warrant tracked three innocent users to or from private spaces, including
residences, a school, and a hospital. Id. at 923–24. Chatrie’s expert showed how this
information, when combined with publicly available information, allowed him to easily
deduce those individuals’ identities. Id.8
Some of my colleagues believe that because a two-hour snippet of Location History
is too short to “reveal intimate details through habits and patterns,” like the aerial
surveillance footage in Leaders of a Beautiful Struggle v. Baltimore Police Department,
2 F.4th 330, 341 (4th Cir. 2021), it cannot reveal intimate details at all. See Judge
8 Whether the Location History collected here placed Chatrie himself inside a
constitutionally protected space is beside the point. “In Carpenter, the Supreme Court’s
analysis of whether the Government’s access of the defendant’s CSLI impeded his
reasonable expectation of privacy was not based on a review of the specific results of the
search in that case.” United States v. Smith, 110 F.4th 817, 834 n.8 (5th Cir. 2024) (citing
Carpenter, 585 U.S. at 309–13). Instead, “[t]he question was whether the technology
utilized by law enforcement had the capability of providing data that offered ‘an all-
encompassing record of [a person’s] whereabouts,’ regardless of whether that person
actually entered spaces that are traditionally considered protected under the Fourth
Amendment.” Id. (quoting Carpenter, 585 U.S. at 311).
Similarly, Kyllo rejected the argument that the search of heat waves emanating from
a home did not implicate the Fourth Amendment if the search did not reveal intimate
details. That argument, Justice Scalia explained, was not only “wrong in principle,” but
also “impractical” because “no police officer would be able to know in advance whether
his through-the-wall surveillance picks up ‘intimate’ details—and thus would be unable to
know in advance whether it is constitutional.” Kyllo, 533 U.S. at 38–39. Likewise, when
police drew up a geofence that included private spaces, they could not predict whether
Chatrie would be shown to have entered those spaces. The Government cannot circumvent
the Constitution merely because, by sheer luck, its target did not stray from the safe zone.
See Arizona v. Hicks, 480 U.S. 321, 325 (1987) (“A search is a search, even if it happens
to disclose nothing but the bottom of a turntable.”).

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Richardson Concurring Op., infra, at 81 n.19. But pattern-based deductions are not the only
way to uncover intimate personal details.9 Another way is to use a surveillance technology
that can follow subjects through walls. See Kyllo, 533 U.S. at 37–39. The aerial surveillance
program at issue in Beautiful Struggle tracked only public movements, so our short-term–
long-term distinction made sense; it takes a lot of grainy aerial footage to deduce intimate
personal details.10 Location History’s accuracy—not to mention its vast retrospective
scope—makes it a much more potent tool.
A few of my colleagues claim that “[a] record of a person’s single, brief trip is no
more revealing than his bank records or telephone call logs.” Judge Richardson Concurring
Op., infra, at 81. Respectfully, that is wrong on multiple accounts. Most obviously, it flat-
out ignores the public surveillance doctrine. Tracking a person’s “single, brief trip” on
public thoroughfares (as in Knotts) is not a search; but tracking even an object’s trip in and
out of a private space (as in Karo) is a search. Compare Knotts, 460 U.S. at 281 with Karo,
468 U.S. at 714–16. Location History is capable of tracking people in and out of private
spaces, with even greater precision than CSLI or the beeper in Karo. More tellingly,
Carpenter expressly recognized that the deeply revealing nature of “cell phone location
9 Indeed, Carpenter made no mention of habits or patterns in discussing the
capabilities of CSLI.
10 The weeks-long aerial surveillance program at issue in Beautiful Struggle
monitored only public spaces during the day, gathered hours-long chunks of image data in
which people appeared as blurry collections of pixels, and stored that data for forty-five
days. Beautiful Struggle, 2 F.4th at 334, 341–42. As a result, the Government had to
decipher individuals’ identities from several pieces of captured data. Id. at 344–45.

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records” puts them in a “qualitatively different category” from “telephone numbers and
bank records.” Carpenter, 585 U.S. at 309. Carpenter’s observation about CSLI is doubly
true of Location History.
In light of the intimately revealing nature of Location History data, the span of time
it covers is of little importance to the Fourth Amendment search analysis. The Government
in Carpenter requested CSLI spanning both seven- and 152-day periods, which revealed,
respectively, two and 127 days of data. Id. at 302. But Carpenter ultimately held that
accessing the shorter span of data was enough to constitute a Fourth Amendment search.
Id. at 310 n.3. The Court’s intimacy analysis drew on Justice Sotomayor’s concurrence in
Jones, which argued that even short-term GPS tracking violates reasonable expectations of
privacy. See id. at 311 (citing Jones, 565 U.S. at 415 (Sotomayor, J., concurring)).
Moreover, Carpenter focused on the nature of the search technology employed, not
the duration of the particular search at bar. Even though the Government only accessed
discrete segments of Carpenter’s CSLI, the Court stressed repeatedly that carriers collect
and store CSLI for “years.” Id. at 312, 313, 315, 319. Location History collects even more
(and more precise) location data, and stores it indefinitely. Applying Carpenter’s logic,
police use of a technology whose very purpose is to generate a dossier of intimately
revealing location data traceable to individuals is a search—even if only a snippet is
ultimately obtained.
At bottom, focusing on the duration of the geofence employed in this particular case
“overlooks the critical issue”: that Location History “is an entirely different species of
business record[,] something that implicates basic Fourth Amendment concerns about

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arbitrary government power much more directly than corporate tax or payroll ledgers.” Id.
at 318. There can be no doubt that even a small amount of such data “provides an intimate
window into a person’s life.” Id. at 311.
D.
Carpenter also found it significant that CSLI searches are “easy, cheap, and efficient
compared to traditional investigative tools.” Carpenter, 585 U.S. at 311. That concern
echoes the Jones concurrences, which warned that low-cost surveillance technologies
could lead to more surveillance and less accountability. Justice Sotomayor’s concurrence
noted that “because GPS monitoring is cheap in comparison to conventional surveillance
techniques and, by design, proceeds surreptitiously, it evades the ordinary checks that
constrain abusive law enforcement practices: ‘limited police resources and community
hostility.’” Jones, 565 U.S. at 415–16 (Sotomayor, J., concurring) (quoting Lidster, 540
U.S. at 426). And Justice Alito added that GPS technology “makes long-term
monitoring”—which was traditionally “difficult and costly and therefore rarely
undertaken”—“relatively easy and cheap.” Id. at 429 (Alito, J., concurring in the
judgment).
Location History is like the GPS monitoring in Jones, only cheaper and more
intrusive. Scholars have estimated that “tracking location by cell phone,” as police did in
Carpenter, “is almost twice as cheap as GPS tracking,” which in turn is “twenty-eight times
cheaper than covert pursuit.” Ohm, supra n.4, at 369 (citing Kevin S. Bankston & Ashkan
Soltani, Tiny Constables and the Cost of Surveillance: Making Cents Out of United States
v. Jones, 123 Yale L.J. Online 335, 354 (2014)). Location History tracking is likely even

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cheaper. “With just the click of a button,” Google—at the Government’s request—“can
access [its] deep repository of historical location information at practically no expense” to
the Government. Carpenter, 585 U.S. at 311. And unlike the tracking device in Jones,
which followed the suspect’s Jeep on public roads, see Jones 565 U.S. at 403, Location
History “follows its [subject] beyond public thoroughfares” and into private spaces,
Carpenter, 585 U.S. at 311.
Plainly, Location History monitoring is vastly cheaper and easier to deploy than
traditional investigative tools. It permits police to access private location data far more
often and much more inconspicuously than the surveillance technologies that have shaped
society’s reasonable expectations of privacy.
* * *
In sum, all four considerations that led Carpenter to conclude that “when the
Government accessed CSLI from the wireless carriers, it invaded Carpenter’s reasonable
expectation of privacy” apply with equal or greater force here. Thus, when the Government
accessed Location History data that was traceable to Chatrie, it invaded his reasonable
expectation of privacy.
III.
The Government—along with a few of my colleagues—would prefer to resolve this
case by “mechanically applying the third-party doctrine,” Carpenter, 585 U.S. at 314. They
contend that Chatrie lacked any reasonable expectation of privacy in his Location History
because he voluntarily conveyed that data to Google.

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That argument is several decades beyond its time. In Carpenter, the Government
argued that police access to CSLI was simply “a garden-variety request for information
from a third-party witness.” Id. at 313. But Carpenter rejected that simplistic, outdated
approach because it “fail[ed] to contend with the seismic shifts in digital technology that
made [detailed location tracking] possible.” Id. We should do the same here.
Carpenter’s Fourth Amendment search analysis proceeded in two parts. Part III.A.
of the Court’s opinion considered the comprehensiveness, retrospectivity, intimacy, and
efficiency of CSLI tracking and concluded that police access to such data violated
Carpenter’s reasonable expectation of privacy. Id. at 310–13. The next section, Part III.B.,
addressed voluntariness—the Government’s argument that Carpenter’s disclosure of CSLI
to his wireless carrier undermined that expectation.11 Id. at 313–16. The Court flatly
rejected that argument for two reasons, both of which apply here.
A.
First, the Court explained that “the revealing nature of CSLI” records put them in a
“distinct category of information” from the kinds of documents to which the third-party
11 Several scholars have noted that Carpenter’s discussion of voluntariness in a
separate rebuttal section suggests that it is the least important factor in the overall
analysis—if indeed it is properly considered a factor at all. See Matthew Tokson, Smart
Meters as a Catalyst for Privacy Law, 72 Fla. L. Rev. Forum 104, 112 (2022) (“Most
scholars view involuntariness not as a requirement but as merely one factor among many
examined in Carpenter. The Court’s discussion of the voluntariness issue . . . was mostly
confined to a single paragraph in a lengthy opinion that largely focused on [other]
factors[.]” (footnote omitted) (collecting sources)); Freiwald & Smith, supra n.4, at 219
(observing that Carpenter established a test made up of only the four factors discussed
above).

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doctrine has been applied. Carpenter, 585 U.S. at 314. The Court in the 1979 case of Smith,
for instance, stressed the “limited capabilities” of a pen register: it does “not acquire the
contents of communications,” nor reveal the caller and call recipient’s “identities, nor
whether the call was even completed.” Smith, 442 U.S. at 741–42 (citation omitted). And
the 1976 case of Miller emphasized that the suspect’s bank records were not “private
papers” or “confidential communications but negotiable instruments to be used in
commercial transactions.” Miller, 425 U.S. at 440, 442. But in 2018, the Carpenter Court
saw “a world of difference between the limited types of personal information addressed in
Smith and Miller and the exhaustive chronicle of location information casually collected
by wireless carriers today.” Carpenter, 585 U.S. at 314.
So too here in 2025. As already discussed at length, Location History is at least as
comprehensive, retrospective, intrusive, and efficient a technology as CSLI. Like CSLI,
Location History is “compiled every day, every moment, over several years.” Id. at 314–
15. It can provide “not just dialed digits, but a detailed and comprehensive record of [a]
person’s movements.” Id. at 309. And it is “effortlessly compiled,” accessible at “the click
of a button” and “at practically no expense.” Id. at 309, 311.
Most fundamentally, what sets CSLI and Location History apart from bank records
and phone logs is that they concern a person’s physical movements. Carpenter recognized
that the Jones concurrences—representing the views of five justices—reflect a “special
solicitude for location information in the third-party context.” Id. at 314. The Carpenter
majority endorsed that concern, expressly acknowledging that CSLI’s capacity to track a

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person’s “physical presence” naturally “implicates privacy concerns far beyond those
considered in Smith and Miller.” Id. at 315. The same is true of Location History.
B.
Second, Carpenter recognized that cell phone users do not, in any “meaningful
sense,” “voluntarily assume the risk of turning over a comprehensive dossier of [their]
physical movements.” Carpenter, 585 U.S. at 315 (cleaned up). The Court began with the
premise that “cell phones and the services they provide are ‘such a pervasive and insistent
part of daily life’ that carrying one is indispensable to participation in modern society.” Id.
at 315 (quoting Riley, 573 U.S., at 385). And “a cell phone logs a cell-site record by dint
of its operation, without any affirmative act on the part of the user beyond powering up.”
Id. at 315.12 Unlike the bank records and phone numbers in Smith and Miller, which were
conveyed to companies by customers’ physical, affirmative acts, the collection of CSLI is
“inescapable and automatic,” such that a cell phone user has “no way to avoid leaving
behind a trail of location data.” Id. at 315, 320.
Sharing Location History—while admittedly not wholly “inescapable”—is not
meaningfully voluntary either. Most importantly, Location History is just one example of
12 Although the CSLI data at issue in Carpenter was only collected at the start and
end of calls, the Court recognized that “in recent years,” companies had also begun
collecting CSLI “from the transmission of text messages and routine data connections,”
resulting in “increasingly vast amounts of increasingly precise CSLI.” Carpenter, 585 U.S.
at 301. Accordingly, the Court considered not only CSLI’s present capacities, but its
emerging potential. See id. at 313 (recognizing that “the rule the Court adopts ‘must take
account of more sophisticated systems that are already in use or in development.’” (quoting
Kyllo, 533 U.S. at 36)).

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a category of personal data–driven services that have become “indispensable to
participation in modern society.” Id. at 315. Nine in ten Americans own a smartphone,13
and countless smartphone apps rely on users’ personal data for both functionality and
revenue. Consequently, Americans face enormous pressure to entrust detailed personal
information to third parties in exchange for services. Tens of millions of citizens “opt” into
services that collect and store years’ worth of intimate information—including location
history, medical records, financial data, family photos, private communications, and
more—on remote servers managed by private corporations. Some of these services are
simply convenient; others are mandated by employers; still others may be critical to a
user’s health or safety. Location History is a particularly useful and widely adopted
example, used by “numerous tens of millions” for everyday services like traffic updates.
Chatrie, 590 F. Supp. 3d at 907.
None of this means that Americans have ceded a reasonable expectation of privacy
in their detailed private information. Smartphone users might reasonably expect that their
deidentified data will be used, in aggregate, to fine-tune targeted advertising. But it would
be a grave misjudgment to conflate an individual’s limited disclosure to Google with an
open invitation to the state. See Jones, 565 U.S. at 418 (Sotomayor, J., concurring) (“I
would not assume that all information voluntarily disclosed to some member of the public
for a limited purpose is, for that reason alone, disentitled to Fourth Amendment
13 Mobile Fact Sheet, Pew Rsch. Ctr. (Nov. 13, 2024),
https://www.pewresearch.org/internet/fact-sheet/mobile [https://perma.cc/QQ7M-
WWLP].

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protection.”); Smith, 442 U.S. at 749 (Marshall, J., dissenting) (“Privacy is not a discrete
commodity, possessed absolutely or not at all. Those who disclose certain facts to a bank
or phone company for a limited business purpose need not assume that this information
will be released to other persons for other purposes.”).
Of course, Location History has to be enabled—and on this slim reed rests the bulk
of the Government’s case. But opting into Location History communicates less about a
customer’s expectations of privacy than the Government would have us believe. “As
anyone with a smartphone can attest, electronic opt-in processes are hardly informed and,
in many instances, may not even be voluntary. Google’s Location History opt-in process
is no different.” United States v. Smith, 110 F.4th 817, 835–36 (5th Cir. 2024) (citations
omitted).
Approving a lucrative location-tracking feature on a smartphone is frictionless by
design. Here, the record indicates that Location History can be enabled within a few
moments of setting up and using an Android device like the one Chatrie used. One of the
first steps in setting up a smartphone that runs on Android is to log into or create a Google
account, a prerequisite for access to many of the smartphone’s features, such as
downloading apps, accessing Google Maps, or syncing Google services like Calendar and
Contacts. The district court found that Google repeatedly prompts its millions of Android
users to opt-in to Location History both upon initial set-up and then “multiple times across
multiple apps.” Chatrie, 590 F. Supp. 3d at 909; see J.A. 128–29.
As the district court recognized, Google’s privacy warnings and descriptive pop-ups
are “limited,” “partially hidden,” and “less than pellucid.” Chatrie, 590 F. Supp. 3d at 936.

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The pop-up text that appears when Google prompts users to opt in explains only that
Location History “[s]aves where you go with your devices,” and that “[t]his data may be
saved and used in any Google service where you were signed in to give you more
personalized experiences. You can see your data, delete it and change your settings at
account.google.com.” Id. at 911–12. Below that, the screen provides the options: “NO
THANKS” or a brightly highlighted “TURN ON.” Id. at 912. It also presents a small
expansion arrow, which, if tapped, displays more information about Location History.14
But a user does not need to click the expansion arrow to opt into Location History. They
can just click “TURN ON.” Through that single tap, Location History is enabled. See id.
At the time Chatrie enabled Location History, this pop-up copy “did not detail . . .
how frequently Google would record [his] location . . . ; the amount of data Location
History collects (essentially all location information); that even if he ‘stopped’ location
tracking it was only ‘paused’ . . . ; or, how precise Location History can be.” Id. at 936. It
did not explain that Location History would automatically and precisely track his location
even when he wasn’t using his phone—and would continue even if he deleted the Google
app through which he enabled it. See id. at 909. Nor did it explain that Location History
would track his location on all of his Google-connected devices—not just those on which
14 The expansion arrow reveals the following additional information: “Location
History saves where you go with your devices. To save this data, Google regularly obtains
location data from your devices. This data is saved even when you aren’t using a specific
Google service, like Google Maps or Search. . . . This data may be saved and used in any
Google service where you were signed in to give you more personalized experiences.”
Chatrie, 590 F. Supp. 3d at 912.

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he enabled the feature. Id. at 909. It certainly didn’t warn him that police could access his
location data. Cf. Jones, 565 U.S. at 417 n.* (Sotomayor, J., concurring) (“[S]mart phone[]
[owners] do not contemplate that these devices will be used to enable covert surveillance
of their movements.”).
Moreover, once a user has opted into Location History, opting out is easier said than
done. “Pausing” Location History “halts the collection of future data,” but “does not delete
information Google has already obtained.” Chatrie, 590 F. Supp. 3d at 912 (quoting J.A.
778). And the record reflects that misleading pop-ups try to dissuade users from pausing
the service by suggesting that various Google apps need Location History in order to
function properly. Id. at 913. These pop-ups “do[] not specifically detail how app
functionality might be limited”; and in fact, most apps “will, indeed, continue to function
without Location History enabled.” Id.
At the time Chatrie enabled Location History, a user could only delete their Location
History through Google’s web browser–based “Timeline” feature. See id. at 913. One
Google employee familiar with that process remarked in an email that it “*feels* like it is
designed to make [deleting Location History] possible, yet difficult enough that people
won’t figure [it] out.” Id. (quoting J.A. 1631). Around the time Chatrie enabled the feature,
Google faced criticism from members of Congress, the media, and Norway’s Consumer
Protection Committee for the lack of transparency in how users enable or disable Location
History. See id. at 909 n.11, 913 & n.16.
In short, the single tap required to enable Location History does not represent a
user’s well-informed or meaningfully voluntary disclosure of “a comprehensive dossier of

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his physical movements.” Carpenter, 585 U.S. at 315. “Although, unlike in Carpenter,
Chatrie apparently took some affirmative steps to enable location history, those steps likely
do not constitute a full assumption of the attendant risk of permanently disclosing one’s
whereabouts during almost every minute of every hour of every day. . . . a user simply
cannot forfeit the protections of the Fourth Amendment for years of precise location
information by selecting ‘YES, I’M IN’ at midnight while setting up Google Assistant,
even if some text offered warning along the way.” Chatrie, 590 F. Supp. 3d at 936.15
* * *
In sum, the third-party doctrine is wholly inadequate to defeat Chatrie’s reasonable
expectation of privacy in Location History data traceable to him. Chatrie—like tens of
millions of Americans—shared that data with Google in exchange for widely used services.
But that “does not mean that the Fourth Amendment falls out of the picture entirely.’”
15 Some of my colleagues argue that this single tap sets Location History apart from
CSLI, such that Carpenter’s reasoning does not apply here. See Judge Richardson
Concurring Op., infra, at 81–83. But the proper comparison in a voluntary-disclosure
analysis is not to CSLI, but to the bank and phone records in Smith and Miller. In Smith,
the individuals under surveillance physically dialed each number police obtained, and the
phone company sent monthly bills listing some of the calls that the companies had
collected. Smith, 442 U.S. at 742 (noting that users “see a list of their long-distance (toll)
calls on their monthly bills”). And in Miller, which was decided before the advent of online
banking, the suspects physically brought the checks and deposit slips at issue to the bank.
Miller, 425 U.S. at 442.
By contrast, once enabled, Location History collects its data inconspicuously and
automatically, “without any affirmative act on the part of the user.” Carpenter, 585 U.S. at
315. A feature that silently documents one’s physical location every two minutes—even if
enabled with a single tap, years ago, in exchange for traffic updates—is not remotely
comparable to the kinds of voluntary disclosures that have been found to undermine
reasonable expectations of privacy under the third-party doctrine.

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Carpenter, 585 U.S. at 314 (quoting Riley, 573 U.S. at 392). Location History—like
CSLI—enables comprehensive, retrospective, intimate, and highly efficient surveillance.
Accordingly, “the fact that the Government obtained the information from a third party
does not overcome [Chatrie’s] claim to Fourth Amendment protection.” Id. at 315–16. The
Government’s acquisition of Chatrie’s Location History “was a search within the meaning
of the Fourth Amendment.” Id. at 316.
IV.
Today, the Court declines to decide whether law enforcement may access Location
History data without a warrant. In doing so, it leaves unresolved a question of immense
constitutional significance: whether the Government may track a person’s movements—
potentially for weeks or months—without judicial oversight. That uncertainty threatens not
only Chatrie’s privacy, but the privacy of all Americans.
Instead of addressing that compelling constitutional issue, this Court takes refuge in
the good-faith exception—and thereby clears the path for widespread, surreptitious police
surveillance. The result is plain. It leaves the door open for law enforcement to monitor
religious services, political protests, gun shows, union meetings, or AA sessions—all
without a warrant, all without judicial oversight or accountability. The technology at issue
here does not merely capture a person’s location at a single moment; it allows the
Government to “reconstruct a person’s movements.” Carpenter, 585 U.S. at 312. At a
minimum, requiring a warrant to obtain such data is necessary to preserve the Fourth
Amendment’s protections.

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Unchecked police surveillance “alter[s] the relationship between citizen and
government in a way that is inimical to democratic society.” Jones, 565 U.S. at 416
(Sotomayor, J., concurring) (citation omitted). A broad range of associational and
expressive freedoms—private conversations, peaceful assembly, investigative
journalism—can be chilled by the knowledge “that the Government may be watching.” Id.
“The prospect of unregulated governmental monitoring will undoubtedly prove disturbing
even to those with nothing illicit to hide.” Smith, 442 U.S. at 751 (Marshall, J.,
dissenting).16
Limiting law enforcement’s access to powerful surveillance technologies “is not
costless. But our rights are priceless. Reasonable minds can differ, of course, over the
proper balance to strike between public interests and individual rights.” United States v.
Smith, 110 F.4th 817, 841 (5th Cir. 2024) (Ho, J., concurring). But the Court’s
unwillingness to confront that question head-on falls short of our duty. The Fourth
Amendment demands more.
16 Ironically, decisions like this one could also hinder legitimate law enforcement
efforts. Shortly after the first oral argument in this case, Google—apparently predicting the
panel majority’s flawed reading of Carpenter—announced its intention to stop centrally
storing users’ Location History data, thereby reducing the potential for legitimate
investigatory uses of Location History data, even with a warrant. See Cyrus Farivar &
Thomas Brewster, Google Just Killed Warrants That Give Police Access to Location Data,
Forbes (Dec. 14, 2023), https://www.forbes.com/sites/cyrusfarivar/2023/12/14/google-
just-killed-geofence-warrants-police-location-data [https://perma.cc/GCP9-QPBG].

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RICHARDSON, Circuit Judge, with whom WILKINSON, NIEMEYER, KING, AGEE,
QUATTLEBAUM, and RUSHING, Circuit Judges, join, concurring:
Okello Chatrie appeals the district court’s denial of his motion to suppress location
data obtained using a geofence warrant. He argues that the geofence warrant violated the
Fourth Amendment because it lacked probable cause and particularity. But obtaining just
two hours of location information that was voluntarily exposed is not a Fourth Amendment
search and therefore doesn’t require a warrant at all. I would therefore affirm Chatrie’s
conviction.
I. Background
This case involves government access to a specialized form of location information
maintained by Google. Understanding the nature of this information, how it is generated,
and how Google obtains it is necessary to understand why the third-party doctrine applies.
Accordingly, I begin with a description of the relevant technology.1
A. Google Location History and Geofence Warrants
Few readers need an introduction to Google, the technology supergiant that offers
products and services like Android, Chrome, Google Search, Maps, Drive, and Gmail. This
case, however, is about a particular setting for mobile devices that Google calls “Location
History.”
1 Google has announced changes to its Location History setting. See Marlo McGriff,
Updates to Location History and New Controls Coming Soon to Maps, Google (Dec. 12,
2023), [https://perma.cc/Y62G-GBUW]. The following description of the facts reflects the
record in this case, not Google’s technology and practices now or in the future.

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Location History is an optional account setting that allows Google to track a user’s
location while he carries his mobile devices. If a user opts in, Google keeps a digital log
of his movements and stores this data on its servers. Google describes this setting as
“primarily for the user’s own use and benefit.” J.A. 131. And enabling it does unlock
several useful features for a user. For instance, he can view a “virtual journal” of his past
travels in the “Timeline” feature of the Google Maps app. J.A. 128. He can also obtain
personalized maps and recommendations, find his phone if he loses it, and receive real-
time traffic updates. But Google uses and benefits from a user opting in, too—mostly in
the form of advertising revenue. Google uses Location History to show businesses whether
people who viewed an advertisement visited their stores. It similarly allows businesses to
send targeted advertisements to people in their stores’ proximity.
Location History is turned off by default, so a user must take several affirmative
steps before Google begins tracking and storing his Location History data. First, he must
enable location sharing on his mobile device.2 Second, he must opt in to the Location
History setting on his Google account, either through an internet browser, a Google
application (such as Google Maps), or his device settings (for Android devices). Before
he can activate the setting, however, Google always presents him language that explains
the basics of the service.3 Third, he must enable the “Location Reporting” feature on his
2 For iOS devices, he must also grant location permission to applications capable of
using that information.
3 This text is the same no matter how a user opts in to Location History. It explains
that Location History “[s]aves where you go with your devices,” and that “[t]his data may

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mobile device.4 And fourth, he must sign in to his Google account on that device. Only
when a user follows these steps will Google begin tracking and storing his Location History
data. Roughly one-third of active Google users have enabled Location History.
Even after a user opts in, he maintains some control over his location data. He can
review, edit, or delete any information that Google has already obtained. So, for instance,
he could decide he only wants to keep data for certain dates and to delete the rest. Or he
could decide to delete everything. Google also allows him to pause (i.e., disable) the
collection of future Location History data.5 Whatever his choice, Google will honor it.
From start to finish, then, the user controls how much Google tracks and stores his Location
History data.
Once a user enables Location History, Google constantly monitors his location
through GPS, even when he isn’t using his phone.6 And if he has an Android phone, he
be saved and used in any Google service where you were signed in to give you more
personalized experiences. You can see your data, delete it and change it in your settings at
account.google.com.” J.A. 1564. It also presents an expansion arrow, which, if tapped by
the user, displays more information about Location History. For instance, it explains that
“Google regularly obtains location data from your devices . . . even when you aren’t using
a specific Google service.” J.A. 1565.
4 Location Reporting allows a user to control which devices in particular will
generate Location History information. So a user could enable Location History at the
account level but then disable Location Reporting for a particular device. That device then
would not generate Location History data.
5 Additionally, if a user disables location sharing on his device, that device will
cease sharing location information with Location History, even if Location History and
Location Reporting remain enabled.
6 On average, Google logs a device’s location every two minutes.

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can turn on another setting—“Google Location Accuracy”—that enables Google to
determine his location using more inputs than just GPS, such as Wi-Fi access points and
mobile networks. As a result, Location History can be more precise than other location-
tracking mechanisms, including cell-site location information. But whether Google
Location Accuracy is activated or not, Location History’s power should not be
exaggerated. In the end, it is only an estimate of a device’s location. So when Google
records a set of location coordinates, it includes a value (measured in meters) called a
“confidence interval,” which represents Google’s confidence in the accuracy of the
estimate.7 Google represents that for any given location point, there is a 68% chance that
a user is somewhere within the confidence interval.
Google stores all Location History data in a repository called the “Sensorvault.”
The Sensorvault assigns each device a unique identification number and maintains all
Location History data associated with that device. Google then uses this data to build
aggregate models to assist applications like Google Maps.
In 2016, Google began receiving “geofence warrants” from law enforcement
seeking to access location information. A geofence warrant requires Google to produce
Location History data for all users who were within a geographic area (called a geofence)
during a particular time period.8 Since 2016, geofence requests have skyrocketed: Google
7 For example, if the confidence interval is one hundred meters, then Google
estimates that a user is likely within a one-hundred-meter radius of the coordinates.
8 Geofence warrants seek only Location History data and no other forms of location
information, so they only affect people who had this feature enabled at the requested time
and place.

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claims it saw a 1,500% increase in requests from 2017 to 2018 and a 500% increase from
2018 to 2019. Concerned with the potential threat to user privacy, Google consulted
internal counsel and law enforcement agencies in 2018 and developed its own three-step
procedure for responding to geofence requests. Since then, Google has objected to any
geofence request that disregards this procedure.
Google’s procedure works as follows: At Step One, law enforcement obtains a
warrant that compels Google to disclose an anonymous list of users whose Location
History shows they were within the geofence during a specified timeframe. But Google
does not keep any lists like this on hand. So it must first comb through its entire Location
History repository to identify users who were present in the geofence. Google then gives
law enforcement a list that includes for each user an anonymized device number, the
latitude and longitude coordinates and timestamp of each location point, a confidence
interval, and the source of the stored Location History (such as GPS or Wi-Fi). Before
disclosing this information, Google reviews the request and objects if Google deems it
overly broad.
At Step Two, law enforcement reviews the information it receives from Google. If
it determines that it needs more, then law enforcement can ask Google to produce
additional location coordinates. This time, the original geographical and temporal limits
no longer apply; for any user identified at Step One, law enforcement can request
information about his movements inside and outside the geofence over a broader period.
Yet Google generally requires law enforcement to narrow its request for this more
expansive location data to only a subset of the users pinpointed in Step One.

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Finally, at Step Three, law enforcement determines which individuals are relevant
to the investigation and then compels Google to provide their account-identifying
information (usually their names and email addresses). Here, too, Google typically
requires law enforcement to taper its request from the previous step, so law enforcement
can’t merely request the identity of every user identified in Step Two.
B. Facts
On May 20, 2019, someone robbed the Call Federal Credit Union in Midlothian,
Virginia. The suspect carried a gun and took $195,000 from the bank’s vault. He then fled
westward before police could respond.
The initial investigation into the robbery proved unfruitful. When Detective Joshua
Hylton arrived at the scene, he interviewed witnesses and reviewed the bank’s security
footage. But these failed to reveal the suspect’s identity. And after chasing down two
dead-end leads, Detective Hylton seemed to be out of luck.
Yet there was one thing Detective Hylton still hadn’t tried. He saw on the security
footage that the suspect had carried a cell phone during the robbery. In the past, Detective
Hylton had sought and obtained three separate geofence warrants after consulting
prosecutors. So on June 14, 2019, he applied for and obtained a geofence warrant from the
Chesterfield County Circuit Court of Virginia.
The warrant drew a geofence with a 150-meter radius covering the bank. It then
laid out the three-step process by which law enforcement would obtain location
information from Google. At Step One, Google would provide anonymized Location
History information for all devices that appeared within the geofence from thirty minutes

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before to thirty minutes after the bank robbery. This information would include a
numerical identifier for each account. At Step Two, law enforcement would “attempt[] to
narrow down that list” to a smaller number of accounts and provide the narrowed list to
Google. J.A. 116. Google would then disclose anonymized location data for all those
devices from one hour before to one hour after the robbery. But unlike the Step One
information, the Step Two information would be unbounded by the geofence. Finally, at
Step Three, law enforcement would again attempt to shorten the list, and Google would
provide the username and other identity information for the requested accounts.
In response to the warrant, Google first provided 209 location data points from
nineteen accounts that appeared within the geofence during the hour-long period.
Detective Hylton then requested Step Two information from nine accounts identified at
Step One. Google responded by producing 680 data points from these accounts over the
two-hour period. Finally, Detective Hylton requested the subscriber information for three
accounts, which Google provided. One of these accounts belonged to Okello Chatrie.9
C. Procedural History
On September 17, 2019, a grand jury in the Eastern District of Virginia indicted
Chatrie for (1) forced accompaniment during an armed credit union robbery, in violation
of 18 U.S.C. §§ 2113(a), (d), and (e); and (2) using, carrying, or brandishing a firearm
during and in relation to a crime of violence, in violation of § 924(c)(1)(A). Chatrie was
9 According to Google’s records, Chatrie created a Google account on August 20,
2017. He later opted in to Location History from a Samsung smartphone on July 9, 2018.

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arraigned on October 1, 2019, and pleaded not guilty. He then moved to suppress the
evidence obtained using the geofence warrant.
On March 3, 2022, the district court denied Chatrie’s motion to suppress. Although
the court voiced concern about the threat geofence warrants pose to user privacy, it declined
to resolve whether the geofence evidence was obtained in violation of the Fourth
Amendment. Rather, the court denied the motion to suppress based on the good-faith
exception to the exclusionary rule. See United States v. Leon, 468 U.S 897 (1984).
Chatrie subsequently entered a conditional guilty plea and was sentenced to 141
months’ imprisonment and 3 years’ supervised release. This timely appeal followed.
II. Discussion
Chatrie asks us to hold that the geofence warrant violated his Fourth Amendment
rights and that the fruits of the warrant should be suppressed. He argues that the
government conducted a Fourth Amendment search because it invaded his reasonable
expectation of privacy in his location information. He further claims that the geofence
warrant authorizing the search was invalid for lack of probable cause and particularity.
Finally, he asserts that the good-faith exception to the exclusionary rule does not apply to
this warrant.
The district court denied Chatrie’s motion to suppress based on the good-faith
exception. I agree that the motion should have been denied, but for an antecedent reason:
Chatrie did not have a reasonable expectation of privacy in two hours’ worth of Location
History data voluntarily exposed to Google. So the government did not conduct a search
when it obtained this information from Google, and so no warrant was required at all. The

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district court should be affirmed on that straightforward basis. See United States v. Smith,
395 F.3d 516, 519 (4th Cir. 2005) (holding that we may affirm a district court “on any
grounds apparent from the record”).
A. Carpenter, Beautiful Struggle, and the Third-Party Doctrine
The Fourth Amendment protects “[t]he right of the people to be secure in their
persons, houses, papers, and effects, against unreasonable searches and seizures.” U.S.
Const. amend. IV. To trigger its protections, the government must conduct a “search” (or
“seizure”) covered by the Fourth Amendment. That’s the first step in a Fourth Amendment
search analysis, and this case should not get past it.
“For much of our history, Fourth Amendment search doctrine was ‘tied to common-
law trespass’ and focused on whether the government ‘obtains information by physically
intruding on a constitutionally protected area.’” Carpenter v. United States, 585 U.S. 296,
304 (2018) (quoting United States v. Jones, 565 U.S. 400, 405, 406 n.3 (2012)). This
trespass-based approach remains alive and well to this day. See, e.g., Jones, 565 U.S. at
405–08.
But as American society changed and technology developed, so too did the
government’s ability to intrude on sensitive areas. Carpenter, 585 U.S. at 305; see
generally Orin Kerr, The Digital Fourth Amendment (2025). So the Supreme Court birthed
a new privacy-based framework in Katz v. United States, 389 U.S. 347 (1967). Under Katz,
a search occurs when the government invades an individual’s reasonable expectation of
privacy. Id. at 351; id. at 360 (Harlan, J., concurring); see also Smith v. Maryland, 442
U.S. 735, 740 (1979). This privacy-based approach augments the prior, trespass-based

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approach by providing another way to identify a Fourth Amendment search. See Jones,
565 U.S. at 405–08; Carpenter, 585 U.S. at 304.
Though sweeping, Katz’s reasonable-expectation framework is not boundless. One
important limit on its scope is the “third-party doctrine.” The Supreme Court has long
recognized that “a person has no legitimate expectation of privacy in information he
voluntarily turns over to third parties.” Smith, 442 U.S. at 743–44. This is because he
“takes the risk, in revealing his affairs to another, that the information will be conveyed by
that person to the Government.” United States v. Miller, 425 U.S. 435, 443 (1976). And
it holds true “even if the information is revealed on the assumption that it will be used only
for a limited purpose and the confidence placed in the third party will not be betrayed.” Id.
Thus, in Miller, the Court held that the government did not conduct a search when it
obtained an individual’s bank records from his bank, since he voluntarily exposed those
records to the bank in the ordinary course of business. Id. in 443. Likewise, in Smith, the
Court held that the government did not conduct a search when it used a pen register to
record outgoing phone numbers dialed from a person’s telephone, because he voluntarily
conveyed those numbers to his phone company when placing calls. 442 U.S. at 742.10
Despite its clear mandate, the third-party doctrine has proved difficult to implement
in the digital age. After all, “people reveal a great deal of information about themselves to
10 Of course, Miller and Smith were not the only cases to invoke this principle. The
Court has applied the third-party doctrine to other kinds of information, too, including
incriminating conversations with undercover agents, United States v. White, 401 U.S. 745,
749–52 (1971), and tax documents given to an accountant, Couch v. United States, 409
U.S. 322, 335 (1973).

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third parties in the course of carrying out mundane tasks.” Jones, 565 U.S. at 417
(Sotomayor, J., concurring). If they lack Fourth Amendment protections for any
electronically shared data, then the government could access whole swaths of private
information free from constitutional scrutiny.
The Supreme Court addressed this tension in a series of cases involving the
government’s use of location-tracking technology. First, in United States v. Knotts, the
Court held that the government did not conduct a search when it placed a tracking device
in a container purchased by one of Knotts’s coconspirators and used it to monitor his short
trip to Knott’s cabin. 460 U.S. 276, 278–80 (1983). The Court explained that “[a] person
traveling in an automobile on public thoroughfares has no reasonable expectation of
privacy in his movements from one place to another,” since he “voluntarily convey[s]
[them] to anyone who want[s] to look.” Id. at 281. The use of the tracker merely
“augment[ed]” existing police capabilities and “amounted principally to the following of
an automobile on public streets and highways.” Id. at 281–82. Yet the Court reserved
whether it would treat long-term surveillance differently. Id. at 283–84.11
11 Separately, the Court held that police did not conduct a search when they observed
the beeper on the premises of Knotts’s cabin. Knotts, 460 U.S. at 284–85. “[T]here is no
indication,” the Court explained, “that the beeper was used in any way to reveal
information as to the movement of the drum within the cabin, or in any way that would not
have been visible to the naked eye from outside the cabin.” Id. at 285. So the government
did not invade Knott’s reasonable expectation of privacy in his home when it observed the
beeper on his property.
Yet the Court reached the opposite result one year later in United States v. Karo,
468 U.S. 705 (1984). Karo, like Knotts, involved police use of a beeper to monitor the
movement of a container; only this time, officers used it to determine whether the container
remained inside a home rented by several of the defendants. Id. at 709–10. The Court held

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This issue later resurfaced in Jones. There, the government attached a GPS device
to Jones’s automobile and used it to track his movements for twenty-eight days. Jones,
565 U.S. at 402–04. Applying the original property-based approach, the Court decided
that the government’s physical trespass on Jones’s vehicle amounted to a search. Id. at
404–05. But in separate opinions, five Justices would have held that “longer term GPS
monitoring in investigations of most offenses impinges on expectations of privacy”—even
though a person’s movements are seemingly shared with third parties. Id. at 430 (Alito, J.,
concurring in the judgment); id. at 415 (opinion of Sotomayor, J.). Such long-term
monitoring violates reasonable expectations of privacy because “society’s expectation has
been that law enforcement agents and others would not—and indeed, in the main, simply
could not—secretly monitor and catalogue every single movement of an individual’s car
for a very long period.” Id. at 430 (opinion of Alito, J.).
After Jones, it was unclear how the Court would decide a case involving long-term
monitoring without a physical trespass. The Court eventually considered this issue in
that this use of the beeper “violate[d] the Fourth Amendment rights of those who ha[d] a
justifiable interest in the privacy of the residence.” Id. at 714. The beeper allowed the
government to obtain information that it otherwise could not have obtained—that the item
was still inside the house—without entering the home itself, which would have required a
warrant. Id. at 715. It therefore intruded on the reasonable expectation of privacy of all
who had a Fourth Amendment interest in that home. Id. at 719 (ruling that the evidence
was inadmissible against “those with privacy interests in the house”); see also Kyllo v.
United States, 533 U.S. 27, 40 (2001) (“Where, as here, the Government uses a device that
is not in general public use, to explore details of the home that would previously have been
unknowable without physical intrusion, the surveillance is a ‘search’ and is presumptively
unreasonable without a warrant.”). But see Karo, 468 U.S. at 716 n.4 (distinguishing
Rawlings v. Kentucky, 448 U.S. 98 (1980), since the defendant in that case did not have a
reasonable expectation of privacy in the place searched).

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Carpenter. Carpenter involved government access to historical cell-site location
information (“CSLI”)—a time-stamped record that is automatically generated every time
any cell phone connects to a cell site. 585 U.S. at 300–01. The government requested—
without a warrant—7 days’ worth of Carpenter’s historical CSLI from one wireless carrier
and 152 days’ worth from another. Id. at 302.12 It then used this information to tie him to
the scene of several robberies. Id. Carpenter moved to suppress the evidence, arguing that
the government had conducted a search without the necessary warrant. Id.
The Court began by noting that government access to CSLI “does not fit neatly
under existing precedents” but “lie[s] at the intersection of two lines of cases, both of which
inform our understanding of the privacy interests at stake.” Id. at 306. Starting with the
location-tracking cases, the Court found that CSLI “partakes of many of the qualities of”—
and in some ways, exceeds—“the GPS monitoring we considered in Jones.” Id. at 309–
13. The unprecedented surveillance capabilities afforded by CSLI, retrospective over days,
reveal—directly and by deduction—a broad array of private information. Id. at 310–12.
The Court thus explained that CSLI provides law enforcement “an all-encompassing record
of the holder’s whereabouts” over that period, id. at 311, allowing it to peer into a person’s
“privacies of life,” including “familial, political, professional, religious, and sexual
associations.” Id. (first quoting Riley v. California, 573 U.S. 373, 403 (2014); and then
quoting Jones, 565 U.S. at 415 (opinion of Sotomayor, J.)). Such access—at least, to seven
12 Although the government requested 7 days’ worth of CSLI from one wireless
carrier and 152 days’ worth from the other, it received only 2 days’ worth from the former
and 127 days’ worth from the latter. Carpenter, 585 U.S. at 302.

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days’ worth of CSLI—invades the reasonable expectation of privacy individuals have “in
the whole of their physical movements.” Id. at 310 & n.3.
That Carpenter “shared” his CSLI with his wireless carriers didn’t change the
Court’s conclusion. Id. at 314. Rejecting the government’s invocation of the third-party
doctrine, the Court found that the rationales that historically supported the doctrine did not
apply to the facts at issue. Id. It first considered “‘the nature of the particular documents
sought’ to determine whether ‘there is a legitimate “expectation of privacy” concerning
their contents.’” Id. (quoting Miller, 425 U.S. at 442). And it found that, unlike the bank
records in Miller or the pen register in Smith, CSLI is extremely revealing of a person’s
private life. Id. at 314–15 (noting that CSLI is a “detailed chronicle of a person’s physical
presence compiled every day, every moment, over several years”). The government’s
access of such a large quantity of detailed information therefore “implicates privacy
concerns far beyond those considered in Smith and Miller.” Id. at 315.
The Court then found that Carpenter did not voluntarily expose this “comprehensive
dossier of his physical movements” to his wireless carriers. Id. Rather, “a cell phone logs
a cell-site record by dint of its operation, without any affirmative act on the part of the user
beyond powering up.” Id. Put differently, having and operating a cell phone automatically
and necessarily requires the transmission of one’s CSLI to the wireless carrier. And cell
phones “are ‘such a pervasive and insistent part of daily life,’” the Court explained, “that
carrying one is indispensable to participation in modern society.” Id. (quoting Riley, 573
U.S. at 385). So “in no meaningful sense does the user voluntarily ‘assume[] the risk’ of
turning over” this information. Id. (second alteration in original) (quoting Smith, 442 U.S.

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at 745). The Court thus declined to extend the third-party doctrine to overcome Carpenter’s
Fourth Amendment protection. Id.
The Court emphasized that its holding was “a narrow one.” Id. at 316. It did not
decide how the Fourth Amendment applies to other forms of data collection, like real-time
(as opposed to historical) CSLI or “tower dumps” (i.e., records of phones connected to a
particular cell tower over a given period). Id. Nor did it jettison the third-party doctrine’s
application in other contexts. Id. All it held was that the government’s acquisition of at
least seven days’ worth of historical CSLI is a search within the meaning of the Fourth
Amendment. Id. at 316, 310 n.3.
Three years later, we clarified the scope of Carpenter’s holding in Leaders of a
Beautiful Struggle v. Balt. Police Dep’t, 2 F.4th 330 (4th Cir. 2021) (en banc). Beautiful
Struggle involved a Fourth Amendment challenge to the City of Baltimore’s aerial-
surveillance program. Id. at 333. The program captured aerial photos of thirty-two square
city miles every second for “at least 40 hours a week, obtaining an estimated twelve hours
of coverage of around 90% of the city each day.” Id. at 334. We interpreted Carpenter to
“solidif[y] the line between short-term tracking of public movements—akin to what law
enforcement could do ‘[p]rior to the digital age’—and prolonged tracking that can reveal
intimate details through habits and patterns.” Id. at 341 (second alteration in original)
(quoting Carpenter, 585 U.S. at 310). And we held that Baltimore’s program crossed that
line because it afforded the government retroactive access to a “detailed, encyclopedic”
record of every person’s movement in the city across days and weeks. Id. (quoting
Carpenter, 585 U.S. at 309). The sheer breadth of this information “enable[d] deductions

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about ‘what a person does repeatedly, what he does not do, and what he does ensemble,’
which ‘reveal[s] more about a person than does any individual trip viewed in isolation.’”
Id. at 342 (second alteration in original) (quoting United States v. Maynard, 615 F.3d 544,
562–63 (D.C. Cir. 2010)). So we held that, when it accessed this information, the
government intruded on reasonable expectations of privacy and thereby conducted a
search. Id. at 346.13
B. Application
Relying on Carpenter, Chatrie argues that the government conducted a search when
it obtained his Location History data from Google.14 I disagree. Carpenter identified two
rationales that justify applying the third-party doctrine: the limited degree to which the
information sought implicates privacy concerns and the voluntary exposure of that
information to third parties. Both rationales apply here.15 Because Chatrie did not have a
reasonable expectation of privacy in the two hours’ worth of Location History data that
13 The government did not invoke the third-party doctrine in Beautiful Struggle.
14 Chatrie does not argue that the government conducted a search when it obtained
his subscriber information from Google at Step Three of the geofence warrant process.
This is probably because we have already held that individuals do not have a reasonable
expectation of privacy in subscriber information they provide to an internet provider. See
United States v. Bynum, 604 F.3d 161, 164 (4th Cir. 2010).
15 Because both rationales apply here, I need not decide whether the voluntary
disclosure of more expansive data would take a case outside the third-party doctrine. See
Carpenter, 585 U.S. at 314–15 (holding that the third-party doctrine did not apply to the
involuntary disclosure of expansive data).

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law enforcement obtained from Google at Step Two, I would find that the government did
not conduct a search by obtaining his information at Steps One or Two.16
Start with the nature of the information sought. Carpenter, 585 U.S. at 314. At
Step Two, the government requested and obtained only two hours’ worth of Chatrie’s
Location History data.17 By no means was this an “all-encompassing record of [Chatrie’s]
whereabouts . . . provid[ing] an intimate window into [his] person[al] life.” Carpenter,
585 U.S. at 311. All the government had was an “individual trip viewed in isolation,”
which, standing alone, was not enough to “enable[] deductions about ‘what [Chatrie] does
16 By focusing our inquiry at Step Two, we consider the broadest set of information
about Chatrie that was provided to the government. At Step Two the government obtained
more information about Chatrie than at Step One. But because the two hours of data the
police accessed at Step Two did not reveal a “detailed, encyclopedic” chronicle of Chatrie’s
life, the smaller dataset accessed at Step One didn’t either.
17 Chatrie suggests that we overlook the relevant dataset: All the data in Sensorvault
that Google trawled to find the narrower set of information it gave the police. This
argument relies on the premise that Google performed a Fourth Amendment search just by
digging through its own data, most of which it never turned over. But precedent squarely
forecloses this argument. See Beautiful Struggle, 4 F.4th at 344 (“Carpenter was clear on
that issue: a search took place ‘when the Government accessed CSLI from the wireless
carriers.’” (quoting Carpenter, 585 U.S. at 313) (emphasis added)). Whether we focus on
Step One or Step Two, the right question is what information Google gave to the
government, not what data Google perused to find that information.
This mistake of considering the Fourth Amendment search to be Google’s efforts to
locate information in its database does appear to have animated the Fifth Circuit’s decision
in United States v. Smith, 110 F.4th 817, 836–38 (5th Cir. 2024). Cf. Orin Kerr, The Fifth
Circuit Shuts Down Geofence Warrants—And Maybe a Lot More, The Volokh Conspiracy
(Aug. 13, 2023) (finding Smith’s general-warrant-by-Google theory “not just wrong, but
basically bananas”).

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repeatedly, what he does not do, and what he does ensemble.’”18 Beautiful Struggle, 2
F.4th at 342 (quoting Maynard, 615 F.3d at 562–63). The information obtained was
therefore far less revealing than that obtained in Jones, Carpenter, or Beautiful Struggle
and more like the short-term public movements in Knotts, which the Court found were
“voluntarily conveyed to anyone who wanted to look.” Carpenter, 585 U.S. at 314
(quoting Knotts, 460 U.S. at 281).19 A record of a person’s single, brief trip is no more
revealing than his bank records or telephone call logs. See Miller, 425 U.S. at 442; Smith,
442 U.S. at 742. Chatrie thus did not have a “legitimate ‘expectation of privacy,’” in the
information obtained by the government, so the first rationale for the third-party doctrine
applies here. Carpenter, 585 U.S. at 314 (quoting Miller, 425 U.S. at 442).
Furthermore, Chatrie voluntarily exposed his location information to Google by
opting in to Location History. Id. at 315. Consider again how Location History works.
18 Chatrie raises the possibility that a geofence warrant could reveal a person’s
movements within a constitutionally protected space, like his home. See Karo, 468 U.S.
at 716–17; Kyllo, 533 U.S. at 40. The district court expressed similar concerns and noted
that the instant geofence warrant included potentially sensitive locations within its radius.
But this is an issue for future cases, not the one before us. Chatrie does not contend that
the warrant revealed his own movements within his own constitutionally protected space.
And to the extent that it might have captured his or others’ movements in another person’s
protected space, Chatrie lacks standing to assert their potential Fourth Amendment claims.
See Rakas v. Illinois, 439 U.S. 128, 133–34 (1978); Brown v. United States, 411 U.S. 223,
230 (1973).
19 Chatrie argues that the amount of information obtained shouldn’t matter, given
the accuracy with which Location History can estimate a user’s location. Yet the question
is not whether the government knew with exact precision what Chatrie did on an
“individual trip viewed in isolation,” Beautiful Struggle, 2 F.4th at 342 (quoting Maynard,
615 F.3d at 562), but whether it gathered enough information from many trips to “reveal
intimate details through habits and patterns,” id. at 341. That was not the case here.

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Location History is an optional setting that adds extra features, like traffic updates and
targeted advertisements, to a user’s experience. But it is “off by default” and must be
affirmatively activated by a user before Google begins tracking and storing his location
data. J.A. 1333–34. Of course, once Google secures this consent, it monitors his location
at all times and across all devices. Yet even then, Google still affords the user ultimate
control over how his data is used: If he changes his mind, he can review, edit, or delete the
collected information and stop Google from collecting more. Whether Google tracks a
user’s location, therefore, is entirely up to the user himself. If Google compiles a record
of his whereabouts, it is only because he has authorized Google to do so.
Nor is a user’s consent secured in ignorance, either. See Carpenter, 585 U.S. at 314
(explaining that the third-party doctrine applies to information “knowingly shared with
another”). To the contrary, the record shows that Google provides users with ample notice
about the nature of this setting. Before Google allows a user to enable Location History, it
first displays text that explains the basics of the service. The text states that enabling
Location History “[s]aves where you go with your devices,” meaning “[t]his data may be
saved and used in any Google service where you were signed in to give you more
personalized experiences.” It also informs a user about his ability to view, delete, or change
his location data.20 A user cannot opt in to Location History without seeing this text.
So unlike with CSLI, a user knowingly and voluntarily exposes his Location History
data to Google. First, Location History is not “‘such a pervasive and insistent part of daily
20 Google provides additional notice of this setting in its Privacy Policy.

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life’ that [activating it] is indispensable to participation in modern society.” Carpenter,
585 U.S. at 315 (quoting Riley, 573 U.S. at 385). Carpenter found that it is impossible to
participate in modern life without a cell phone. Id. But the same cannot be said of Location
History. While Location History offers a few useful features to a user’s experience, its
activation is unnecessary to use a phone or even to use apps like Google Maps. Chatrie
gives us no reason to think that these added features are somehow indispensable to
participation in modern society and that his decision to opt in was therefore involuntary.
That two-thirds of active Google users have not enabled Location History is strong
evidence to the contrary. Cf. Riley, 573 U.S. at 385 (noting that, as of 2014, “a significant
majority of American adults” owned smartphones). Thus, a user can decline to use
Location History and still participate meaningfully in modern society.
Second, unlike CSLI, Location History data is obtained by a user’s affirmative act.
Carpenter noted that “a cell phone logs a cell-site record by dint of its operation, without
any affirmative act on the part of the user beyond powering up.” 585 U.S. at 315. But
Location History is off by default and can be enabled only by a user’s affirmative act. A
person need not go off the grid by “disconnecting [his] phone from the network . . . to
avoid” generating Location History data; instead, he can simply decline to opt in and
continue using his phone as before. See id. Thus, “in [every] meaningful sense,” a user
who enables Location History “voluntarily ‘assume[s] the risk’” of turning over his
location information. Id. (quoting Smith, 442 U.S. at 745). So the second rationale for the
third-party doctrine applies here, too.

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The third-party doctrine therefore squarely governs this case. The government
obtained only two hours’ worth of Chatrie’s location information, which could not reveal
the privacies of his life. And Chatrie opted in to Location History on July 9, 2018. This
means that he knowingly and voluntarily chose to allow Google to collect and store his
location information. In so doing, he “t[ook] the risk, in revealing his affairs to [Google],
that the information [would] be conveyed by [Google] to the Government.” Miller, 425
U.S. at 443. He cannot now claim to have had a reasonable expectation of privacy in this
information. See Smith, 442 U.S. at 743–44. The government therefore did not conduct a
search when it obtained the data.21
* * *
The Fourth Amendment is an important safeguard to individual liberty. But its
protections are not endless. To transgress its command, the government must first conduct
21 Nor has Chatrie shown a property interest in his Location History data. Chatrie
does not cite any positive law (state or federal) that gives him an ownership interest in his
Location History data. See Carpenter, 585 U.S. at 331 (Kennedy, J., dissenting); id. at
353–54 (Thomas, J., dissenting); id. at 402 (Gorsuch, J., dissenting). Nor does he claim
that he could bring a tort suit if this information were stolen. See id. at 353 (Thomas, J.,
dissenting). Instead, he relies largely on the fact that Google describes Location History
as “your information,” J.A. 39 (emphasis added), and as a user’s “virtual journal,” J.A.
128. But this is an incredibly thin reed on which to hang such a bold pronouncement.
Though we issue no opinion on whether Google can create a property interest merely by
saying one exists, Google at least knows how to recognize preexisting property rights when
it wants to. At the time Chatrie opted in to Location History, Google explicitly labelled
digital cloud content as user property. See J.A. 2083 (“You retain ownership of any
intellectual property rights that you hold in that content. In short, what belongs to you stays
yours.”). But Google used no such language to describe its location services. See J.A.
2051 (describing location information as content Google “collect[s]” and omitting mention
of property rights); J.A. 1339–40 (omitting mention of property rights at the initial opt-in).
We therefore cannot hold, based on the record before us, that Chatrie had a property interest
in his Location History data.

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a search. I would hold that the government did not conduct a Fourth Amendment search
when it accessed two hours’ worth of Chatrie’s location information that he voluntarily
exposed to Google.

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TOBY HEYTENS, Circuit Judge, with whom Judges HARRIS and BERNER join,
concurring:
Whether or not there was a Fourth Amendment violation here, I think the district
court rightly declined to prescribe the “strong medicine” of excluding otherwise admissible
evidence. United States v. Janis, 428 U.S. 433, 453 (1976) (quotation marks removed).
“The fact that a Fourth Amendment violation occurred . . . does not necessarily
mean that the exclusionary rule applies.” Herring v. United States, 555 U.S. 135, 140
(2009). Exclusion of unlawfully seized evidence is “not a personal constitutional right, nor
is it designed to redress the injury occasioned by an unconstitutional search.” Davis v.
United States, 564 U.S. 229, 236 (2011) (quotation marks removed). Rather, the
exclusionary rule is a “judicially created remedy” whose “sole purpose . . . is to deter future
Fourth Amendment violations.” United States v. Calandra, 414 U.S. 338, 348 (1974) (first
quote); Davis, 564 U.S. at 236–37 (second quote).
“Real deterrent value is a necessary condition for exclusion, but it is not a sufficient
one.” Davis, 564 U.S. at 237 (quotation marks removed). The Supreme Court’s cases “have
thus limited” the exclusionary “rule’s operation to situations in which [its deterrent]
purpose is thought most efficaciously served.” Id. (quotation marks removed). In particular,
“[t]o trigger the exclusionary rule, police conduct must be sufficiently deliberate that
exclusion can meaningfully deter it, and sufficiently culpable that such deterrence is worth
the price paid by the judicial system” when relevant and reliable evidence is suppressed.
Herring, 555 U.S. at 144. In contrast, when law enforcement officials “act with an
objectively reasonable good-faith belief that their conduct is lawful,” “the deterrence

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rationale loses much of its force, and exclusion cannot pay its way.” Davis, 564 U.S. at 238
(quotation marks removed).
In my view, exclusion is unwarranted here for two related reasons.
First, the legal landscape was uncertain when this investigation happened.
“Responsible law enforcement officers will take care to learn what is required of them
under Fourth Amendment precedent and will conform their conduct to [those] rules.”
Davis, 564 U.S. at 241 (quotation marks removed). But here there were no clear guideposts
to follow. The investigating officer was using “rapidly developing technology” while faced
with a “dearth of court precedent.” United States v. McLamb, 880 F.3d 685, 691 (4th Cir.
2018) (first quote); United States v. Smith, 110 F.4th 817, 840 (5th Cir. 2024) (second
quote). Indeed, when the officer was investigating this case, it appears no court had
examined the validity of (or constitutional restrictions on) geofence warrants.
Second, the officer did what we expect reasonable officers to do when faced with
such uncertainty. The officer knew he “had sought three other geofence warrants in the
past” that magistrates had approved. JA 1349; see United States v. Carpenter, 926 F.3d
313, 318 (6th Cir. 2019) (noting that, at the relevant time, “[t]wo magistrate judges” had
issued orders based on the same statute the Supreme Court later held could not
constitutionally justify obtaining the defendant’s cell-site location information without a
warrant). “Before seeking those warrants,” the officer “consulted with prosecutors, who
approved them.” JA 1349; see McLamb, 880 F.3d at 691 (noting officers had “consulted
with attorneys from the Department of Justice”); Smith, 110 F.4th at 839 (officers “had
conversations with other law enforcement officers and the U.S. Attorney’s Office prior to

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submitting their warrant”). And here, for the fourth time, the officer sought and obtained a
warrant from a judicial officer.
The Supreme Court has said the exclusionary rule should be used to “deter
deliberate, reckless, or grossly negligent conduct, or in some circumstances recurring or
systemic negligence.” Herring, 555 U.S. at 144. Any Fourth Amendment error here did
“not rise to that level.” Id. Indeed, “one can understand” why a reasonable officer “might
have believed” he had done all the Fourth Amendment required. Carpenter, 926 F.3d at
318; see United States v. Katzin, 769 F.3d 163, 177–87 (3d Cir. 2014) (en banc). And
because the investigating officer could have had “an objectively reasonable good-faith
belief that [his] conduct [was] lawful,” I think the district court was right to withhold “the
harsh sanction of exclusion.” Davis, 564 U.S. at 238, 240 (quotation marks removed).

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BERNER, Circuit Judge, with whom Judges GREGORY, WYNN, THACKER, and
BENJAMIN join, and with whom Judge HEYTENS joins as to Parts I, II(A), and II(B),
concurring:
Our Fourth Amendment jurisprudence recognizes that the balance between
individual privacy and public safety is a delicate one. Technology’s threat to that balance
lies at the heart of this case. Prohibiting the government from using geofence warrants in
all but the rarest of cases would unnecessarily frustrate criminal investigations. At the same
time, allowing the government warrantless access to individuals’ non-anonymous location
data would swing the pendulum too far in the other direction.
In this case, the Government used a geofence warrant to investigate a bank robbery.
After early leads failed to generate a suspect, the Government sought information about
individuals whose cellphones were near the scene of the crime. A magistrate granted the
Government’s application for a geofence warrant. Pursuant to this warrant, the Government
sent Google three separate, increasingly probing, requests for Google users’ Location
History data.
In its first request, the Government asked Google to produce a dataset showing
pseudonymized1 Google users’ movements within a 150-meter radius of the bank—the
initial “geofence”—during the one-hour period surrounding the robbery. Because of the
1 Pseudonymization is the process of removing personal identifiers (such as names,
email addresses, and phone numbers) from a dataset and replacing them with identifiers
(such as random alphanumeric codes) that are not tied to individuals’ identities.
Pseudonymized data is not necessarily anonymous, however. Through certain clues or
pieces of information, it may be possible to unmask the personal identities of individuals
contained in a pseudonymized dataset.

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narrow parameters of this request, the pseudonymized Location History was not likely to
be traceable to the identities of particular Google users.
In its second request, the Government sought additional Location History data
unconfined by any geographic boundary. Though the Government asked Google to
produce a pseudonymized dataset, the broad scope of the request meant that the
Government would likely be able to associate that Location History data with the identities
of specific people. The data would, for example, likely show pseudonymized Google users
entering particular homes and offices. Thus, it was not truly anonymous.
Finally, in its third request, the Government expressly asked Google to reveal the
names, email addresses, and phone numbers associated with certain pseudonymized
Google users identified in the second dataset. One of those users was Okello Chatrie.
The Government’s requests raise two Fourth Amendment questions: (1) whether
Chatrie held a reasonable expectation of privacy in his Location History data, and (2) if so,
whether the warrant the Government used to acquire this data was supported by probable
cause.
Unlike our colleagues on the Fifth Circuit, I do not believe that geofence warrants
are categorically unconstitutional. See United States v. Smith, 110 F.4th 817, 838 (5th Cir.
2024). Individuals lack a reasonable expectation of privacy in Location History data that is
truly anonymous, meaning that—as evaluated at the time of the government’s request—
the data is not likely to be traceable to specific individuals. An individual does not have a
reasonable expectation of privacy in the mere fact that a certain number of unknown
individuals were located near a public place at a particular time, even if he happened to be

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one of those individuals. I would thus hold that Government’s first request to Google did
not result in a Fourth Amendment search. Because of the (1) short duration of the request,
(2) limited size of the geofenced area, and (3) public nature of the geofenced area, the
Location History data that the Government initially requested from Google was not likely
to be traceable to any specific individual, including Chatrie. Consequently, the initial
request did not infringe upon Chatrie’s reasonable expectation of privacy.
Under the framework established by the Supreme Court in Carpenter v. United
States, 585 U.S. 296 (2018), however, I would hold that individuals do have a reasonable
expectation of privacy in their non-anonymous Location History data. This includes
pseudonymized data that, based on the parameters of a particular request, is likely to be
traceable to the identities of specific individuals. The Government thus conducted a Fourth
Amendment search when it acquired Chatrie’s non-anonymous Location History data
through its second and third requests to Google.
Before conducting a Fourth Amendment search, law enforcement “must generally
obtain a warrant supported by probable cause.” Carpenter, 585 U.S. at 316. Because the
Government lacked probable cause to search any specific Google user at the time it applied
for the geofence warrant, this warrant was invalid and the Government’s search of Chatrie
violated the Fourth Amendment.
I. Background
On the afternoon of May 20, 2019, an unknown individual robbed a bank in
Virginia. The robber pointed a gun at the bank manager and stole approximately $195,000.

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He then fled the scene before police could respond, and law enforcement was unable to
find him through witness accounts, tips, and security footage.
In reviewing the bank’s security footage, however, a detective noticed that the
robber appeared to have been holding a cellphone when he walked into the bank. Knowing
that Google possesses location data on millions of cellphones, the detective applied for and
obtained a warrant seeking information from Google about all cellphones within a certain
radius of the bank—a perimeter known as a geofence—around the time of the crime.
Google complied with the geofence warrant. Through three separate requests to Google,
the Government ultimately obtained geolocation data that enabled it to identify Chatrie as
the suspect. This appeal concerns Chatrie’s motion to suppress that data.
Google had been keeping a record of Chatrie’s movements through its Location
History tool. Location History automatically records the location of a cellphone, even when
the user is not actively using his phone or receiving incoming messages. To obtain a
phone’s latitude and longitude coordinates, Location History draws from GPS information,
Bluetooth, cellular towers, IP address information, and the signal strength of nearby Wi-Fi
networks. All data collected by Location History is stored in a Google-controlled repository
known as “Sensorvault.” Though individuals can decline to enable Location History,
Google repeatedly prompts users to enable the feature when they open certain mobile apps.
Location History logs comprehensive and precise data from cellphones that enable
location tracking. Location History records a phone’s location approximately every two
minutes. In certain circumstances, Google can estimate a phone’s location down to three
meters. Location History even allows Google to estimate a phone’s elevation, with

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precision that can potentially infer the specific floor of an apartment building where a user
is located. To show a phone’s location, Location History displays a point on a map and
depicts around that point a radius known as a “confidence interval.” The smaller the
radius around a phone’s estimated location, the more confident Google is in that phone’s
exact location. A phone is somewhere inside the given confidence interval over two-thirds
of the time.
Several years ago, Google worked with law enforcement to develop a three-step
process for responding to geofence warrants. Each “step” begins with a new request from
law enforcement to Google. The Government in this case followed Google’s three-step
process. It is worth emphasizing that Google’s three-step process was neither designed nor
mandated by a magistrate. The process merely expresses the preferences and policy of
Google, a private company.
The Government submitted a warrant application that outlined the broad contours
of Google’s three-step process. Under this process, the second and third requests are
necessarily formulated based on Google’s responses to the preceding requests.
Consequently, at the time the Government applied for the geofence warrant, it could not
have explained the specific rationale that would ultimately support its second and third
requests.
At step one, the Government requested pseudonymized data showing all Google
users’ movements within a 150-meter radius of the bank during the one-hour period
surrounding the robbery. The geofence perimeter primarily encompassed public streets. In
response to the Government’s first request, Google produced a pseudonymized dataset that

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consisted of 210 discrete location datapoints across 19 unique phones, meaning that the
Government obtained numerous datapoints from some of those phones.
After reviewing the data that Google provided in response to the first request, the
Government next requested from Google additional Location History data on some of the
users identified within the initial geofence. In its second request, the Government asked
Google to produce two hours of full Location History data—both inside and outside of the
150-meter geofence—generated by nine of the 19 Google users identified pseudonymously
at step one.
After analyzing the additional Location History data that Google produced in
response to the second request, the Government submitted its third and final request. In
this request, the Government asked Google to disclose identifying information—names,
email addresses, and phone numbers—associated with three of the nine pseudonymous
account holders whose data the Government obtained at step two. Google’s response
revealed that one of the three cellphones belonged to Chatrie. The Government ultimately
concluded that Chatrie was the individual responsible for the robbery.
II. Analysis
A. The Third-Party Doctrine and Carpenter
The government conducts a Fourth Amendment search when it invades an
individual’s “reasonable” expectation of privacy. See Katz v. United States, 389 U.S. 347,
360–62 (1967) (Harlan, J., concurring). Courts often refer to this rule as the “Katz test.”
E.g., Kyllo v. United States, 533 U.S. 27, 34 (2001). Before conducting a Fourth

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Amendment search, the government “must generally obtain a warrant supported by
probable cause” particular to the persons or things to be searched. Carpenter, 585 U.S. at
316. Chatrie argues that the Government violated his Fourth Amendment rights when it
obtained his Location History data without a valid warrant. Chatrie cannot rely on the
Fourth Amendment’s protections unless he held a reasonable expectation of privacy in that
Location History data.2
The Katz test applies to all searches and seizures. For a subset of cases within this
Fourth Amendment framework, however, additional principles guide courts in evaluating
whether an expectation of privacy is “reasonable.” “No single rubric definitively resolves
which expectations of privacy” are reasonable. Carpenter, 585 U.S. at 304. “[T]he analysis
is informed by historical understandings of what was deemed an unreasonable search and
seizure when [the Fourth Amendment] was adopted.” Id. at 304–05 (internal quotation
marks and citation omitted).
Where an individual challenges the government’s acquisition of his data from a third
party, courts have traditionally evaluated reasonableness through the “third-party
doctrine,” a framework developed across two Supreme Court cases in the 1970s. Those
cases, United States v. Miller, 425 U.S. 435 (1976), and Smith v. Maryland, 442 U.S. 735
(1979), drew “a line between what a person keeps to himself and what he shares with
others.” Carpenter, 585 U.S. at 307–08. In describing Miller and Smith, the Carpenter
2 Courts often refer to this principle as “Fourth Amendment standing,” but it is not
a jurisdictional requirement and need not be addressed before considering other aspects
of a claim. Byrd v. United States, 584 U.S. 395, 410–11 (2018).

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Court explained, “[w]e have previously held that ‘a person has no legitimate expectation
of privacy in information he voluntarily turns over to third parties.’ That remains true ‘even
if the information is revealed on the assumption that it will be used only for a limited
purpose.’” Id. at 308 (quoting Smith, 442 U.S. at 743–44 (first quote); Miller, 425 U.S. at
443 (second quote) (internal citations omitted)). Under this doctrine, “the Government is
typically free to obtain such information from the recipient without triggering Fourth
Amendment protections.” Id.
In Miller, the Court rejected the assertion that an individual holds a reasonable
expectation of privacy in his bank records. The Court explained that these documents were
“business records of the banks” that were “exposed to [bank] employees in the ordinary
course of business.” 425 U.S. at 440 (first quote), 442 (second quote). In the Court’s view,
these were “not confidential communications but negotiable instruments to be used in
commercial transactions.” Id. at 442.
Three years later, the Court in Smith held that an individual lacks a reasonable
expectation of privacy in the phone numbers he dials. The Court concluded that the
government’s use of a pen register, a device that records the outgoing phone numbers
dialed on a landline telephone, was not a Fourth Amendment search. 442 U.S. at 745–46.
Because the pen register had “limited capabilities,” the Court “doubt[ed] that people in
general entertain any actual expectation of privacy in the numbers they dial.” Id. at 742.
According to the Court, telephone subscribers knew that the numbers they dialed were used
by the telephone company “for a variety of legitimate business purposes,” including routing
calls. Id. at 743.

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In Carpenter, the Court confronted the applicability of the third-party doctrine to
modern data collection. Carpenter, like this case, involved an attempt to identify a robbery
suspect. See 585 U.S. at 301–02. After police arrested several men suspected of robbing
electronics stores, one of the men gave the government the cellphone numbers of his
purported accomplices. Id. One of those numbers belonged to Carpenter. Id.
The government sought Carpenter’s historical cellphone location data. Id. at 301–
02. It requested from telecommunications carriers a form of data known as cell-site location
information (CSLI). Id. at 301. Cell sites, the sets of radio antennas through which
cellphones obtain signals, collect time-stamped records each time a phone taps into a
network. Id. at 302. These CSLI records are generated by “[v]irtually any activity on the
phone . . . including incoming calls, texts, or e-mails and countless other data connections
that a phone automatically makes when checking for news, weather, or social media
updates.” Id. at 315.
Though CSLI can be anonymized, the CSLI provided to law enforcement is not
typically anonymous. It reveals the phone number of each device that connects to a
particular cell site. A cell site is typically mounted to a tower or pole. Id. at 300. Because
cellphones generally connect to the closest cell site, it is possible to determine a phone’s
approximate location at any moment by knowing the cell site to which the phone was
connected. See id. “The precision of this information depends on the size of the geographic
area covered by the cell site. The greater the concentration of cell sites, the smaller the
coverage area.” Id. at 301. CSLI does not distinguish between the locations of the various

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devices connected to a particular cell site. It shows only that a device was within a given
cell site’s coverage area.
The government obtained Carpenter’s CSLI through court orders, which are subject
to a lower standard of proof than search warrants. See id. To obtain a court order, the
government merely needs to put forth “specific and articulable facts showing that there are
reasonable grounds to believe” that the records sought are “relevant and material to an
ongoing criminal investigation.” 18 U.S.C. § 2703(d) (emphasis added). A search warrant,
in contrast, must be supported by “the substantially higher probable cause standard.”
United States v. Graham, 796 F.3d 332, 344 (4th Cir. 2015), rev’d on other grounds, 824
F.3d 421 (4th Cir. 2016) (en banc).
The court orders at issue in Carpenter requested CSLI generated over a lengthy
period of time. The first order sought 152 days of CSLI from one cellphone carrier, which
responded by producing records spanning 127 days. 585 U.S. at 302. The second order
requested seven days of CSLI from another carrier, which produced two days of records.
Id. Carpenter moved to suppress the CSLI data obtained through each of these court orders,
arguing that the government violated the Fourth Amendment by acquiring these records
without search warrants. Id. at 302. The government asserted that under the third-party
doctrine, Carpenter could not claim a legitimate expectation of privacy in CSLI he
knowingly disclosed to his cellphone carriers. See id. at 313.
The Carpenter Court rejected the government’s invocation of the third-party
doctrine. It stated that “there is a world of difference between the limited types of personal
information addressed in Smith and Miller,” the cases that form the core of the third-party

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doctrine, “and the exhaustive chronicle of location information casually collected by
wireless carriers today.” Id. at 314. In light of this distinction, the Court concluded that
“the Government thus is not asking for a straightforward application of the third-party
doctrine, but instead a significant extension of it to a distinct category of information.” Id.
(emphasis added).
The Carpenter Court explained that whether one holds a reasonable expectation of
privacy in data given to a third party depends on: (1) how revealing that data is, and (2)
whether the information was, in practical terms, given to the third party voluntarily. See id.
at 314–15. After evaluating both factors, the Court concluded that Carpenter held a
reasonable expectation of privacy in the CSLI obtained by the government. See id. at 313.
B. Carpenter’s Application to this Case
Applying Carpenter’s two factors to this case, I would hold that law enforcement
conducts a search when it obtains any amount of an individual’s Location History data that
is non-anonymous. This includes Chatrie’s Location History data that the Government

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obtained through its second and third3 requests to Google. These requests sought highly
revealing data, and the record does not establish whether the disclosure of this information
was definitively voluntary.
i. Non-Anonymous Location History Data is Highly Revealing
The Government contends that because Chatrie’s disclosure of his Location History
data to Google was voluntary, he forfeited any expectation of privacy in that data. Yet
3 In asserting that the Government violated his Fourth Amendment rights, Chatrie
analyzes the alleged search as a single endeavor, not in discrete steps. Unlike Judge
Richardson, however, I do not believe Chatrie forfeited any argument that step three was a
Fourth Amendment search. See opinion of RICHARDSON, J., at 79 n.14. The
Government’s request at step three is distinct from the request for subscriber information
at issue in United States v. Bynum, 604 F.3d 161, 162–64 (4th Cir. 2010). In Bynum, a
pre-Carpenter case, this court held that a Fourth Amendment search did not occur where
law enforcement used a subpoena to obtain a Yahoo subscriber’s name and physical
address. See id. at 164. Law enforcement in Bynum requested subscriber information
associated with a public-facing Yahoo screen name—one belonging to a user who had
voluntarily posted his photo, location, sex, and age on his Yahoo profile page. Id.
Here, in contrast, the Government requested the names, email addresses, and phone
numbers associated with private numerical identifiers (Device IDs) created internally by
Google and associated solely with Google users’ Location History data, not with other parts
of their Google accounts. These Device IDs were not publicized by or even known to
individual Google users. The Government was able to learn of these Device IDs only
through responses to its requests for Location History data.
Once the government has obtained a user’s pseudonymized Location History data,
a request that Google reveal that user’s identity is no less a search than had the process
been reversed—i.e., had the Government provided Google with a name and email address
and asked for two hours of that user’s Location History data. That an individual lacks a
reasonable expectation of privacy in the answer to the question at issue in Bynum—
essentially, who is johndoe@yahoo.com?—sheds no light on whether he lacks a reasonable
expectation of privacy in the answer to the entirely distinct question at issue here—who is
the person that traveled in this precise pattern for two hours? The latter, of course, is far
more revealing.

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Carpenter explained that voluntariness is merely one of two considerations under the
third-party doctrine. “Smith and Miller, after all, did not rely solely on the act of sharing.
Instead, they considered ‘the nature of the particular documents sought’ to determine
whether ‘there is a legitimate “expectation of privacy”’ concerning their contents.’” Id. at
314 (emphasis added). Carpenter described “voluntary exposure” as the “second rationale
underlying the third-party doctrine.” Id. at 315. Here, as in Carpenter, “[i]n mechanically
applying the third-party doctrine to this case, the Government fails to appreciate that there
are no comparable limitations on the revealing nature” of historical cellphone location data.
Id.
The revealing nature of Location History data depends on whether it is anonymous.
Though anonymous Location History data is not particularly sensitive, non-anonymous
Location History data is highly revealing. Because pseudonymized location data may be
non-anonymous, evaluating the anonymity of a dataset is not always a straightforward
inquiry.
Pseudonymized location data is not anonymous when it can be linked to a particular
individual. Whether pseudonymized Location History data is likely to be traceable to a
specific person—an inquiry that must be conducted at the time of a request, not post-hoc—
depends on (1) the duration of the request; (2) the size of the search area; and (3) the nature
of the search area. The second and third factors are particularly important. Let’s take an
example. If the government were to look at pseudonymized Location History data
generated within a defined section of I-95 between 7:00 am and 9:00 am on a weekday, it
is not likely to be able to determine the identities of the individual drivers. If, on the other

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hand, the search area were unrestricted or included residential neighborhoods, two hours
of Location History data during that same time period could reveal that a pseudonymized
Google user traveled from a particular home to a particular company’s office building. The
government could readily determine that individual user’s identity by, for instance, looking
at property records and running a LinkedIn search.
This court’s en banc decision in Leaders of a Beautiful Struggle v. Baltimore Police
Department recognized that location data without individual identifiers can still pose a
threat to privacy. 2 F.4th 330, 341–42 (4th Cir. 2021). In that case, the government
contended that an aerial surveillance program did not infringe upon individuals’ reasonable
expectations of privacy because it showed people only as “a series of anonymous dots
traversing a map of Baltimore.” Id. at 342 (quotation omitted). This court emphasized,
however, that the particular movements of these dots, “analyzed with other available
information, will often be enough for law enforcement to deduce the people behind the
pixels.” Id. at 343.
The pseudonymized Location History data obtained through the Government’s first
request was anonymous. In that request, the Government sought data depicting all Google
users’ movements within a 150-meter radius, which encompassed primarily public streets
and stores, over a one-hour timeframe. Absent some stroke of luck for the Government, it
was exceedingly unlikely that Google’s response would reveal the identities of the
pseudonymized individuals within that geofence perimeter, even if “analyzed with other
available information.” Id. Through its second request to Google, however, the
Government obtained two hours of Location History data belonging to nine

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pseudonymized individuals. That Location History data was not confined to any
geographic boundary. At the time of the second request, law enforcement could have
predicted that the pseudonymized data would likely be traceable to Chatrie and the other
Google users. As a result, it was non-anonymous.
Carpenter compels the conclusion that individuals have a reasonable expectation of
privacy in all non-anonymous Location History data, regardless of amount. Carpenter’s
first factor—the revealing nature of the data—directs courts to consider the type of data at
issue rather than the amount. To be sure, the Carpenter Court stated that its holding was
“narrow,” 585 U.S. at 316, and, in a footnote, added that “we need not decide whether there
is a limited period for which the Government may obtain an individual’s historical CSLI
free from Fourth Amendment scrutiny . . . . It is sufficient for our purposes today to hold
that accessing seven days of CSLI constitutes a Fourth Amendment search.” Id. at 310 n.3.
I do not read this disclaimer to suggest that the duration of the request played a significant
role in the Court’s analysis or decision, however. This footnote was in response to the
parties’ “alternative” suggestion “that the acquisition of CSLI becomes a search only if it

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extends beyond a limited period.” Id. The Court’s declining to evaluate this alternative
theory was not tantamount to an endorsement of it.4
In Carpenter, the Court repeatedly analyzed what CSLI technology had the capacity
to reveal, not what it actually revealed in the search at issue. The Court stated that “[t]his
case is not about using a phone or a person’s movement at a particular time. It is about a
detailed chronicle of a person’s physical presence compiled every day, every moment, over
several years.” Id. at 315 (emphasis added) (internal quotation marks omitted). By its own
characterization, then, Carpenter was “about” what the third party collected—
comprehensive data over several years—rather than what the government requested: data
over a seven-day stretch. “The Government’s position fails to contend with the seismic
shifts in digital technology that made possible the tracking of not only Carpenter’s location
but also everyone else’s, not for a short period but for years and years.” Id. at 313
(emphasis added). Further, in responding to Justice Kennedy’s dissent, the majority stated
that Fourth Amendment protection for the “modern-day equivalents of an individual’s own
‘papers’ or ‘effects’ . . . should extend as well to a detailed log of a person’s movements
over several years.” Id. at 319 (emphasis added). “At some point, the dissent should
4 The ambiguous wording in footnote three of Carpenter may further evidence its
relative insignificance. Footnote three states that “[i]t is sufficient for our purposes today
to hold that accessing seven days of CSLI constitutes a Fourth Amendment search.”
Carpenter, 585 U.S. at 310 n.3 (emphasis added). Yet the government accessed only two
days of CSLI from one of the carriers, Sprint, and the Court gave every indication that this
alone constituted a search. “When the Government accessed CSLI from the wireless
carriers, it invaded Carpenter’s reasonable expectation of privacy . . . Sprint Corporation
and its competitors are not your typical witnesses.” Id. at 313.

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recognize that CSLI is an entirely different species of business record.” Id. at 318
(emphasis added).
Evaluating the type of data rather than the amount intuitively makes sense under the
Katz test. An individual’s expectation regarding whether a third-party storage service such
as iCloud will protect his files does not depend on the number of photos or documents
stored. A single file may prove more revealing than dozens of others combined; it is
impossible to know in advance. That is true of non-anonymous Location History data as
well. The government could look through a week of Location History data and learn little
sensitive information about a person, or it could look through two hours of data and learn
that the person attended a protest and a place of worship. See opinion of WYNN, J., at 48.
A warrant must be obtained before a search is conducted, but there is no way of knowing
the sensitivity of a dataset before examining its contents. To align with individuals’ actual
expectations of privacy, Fourth Amendment protections must turn on the type of data—
here, non-anonymous cellphone Location History data—rather than the amount.
Location History data, like CSLI, is more revealing than any retrospective
surveillance method available at the time the Fourth Amendment was adopted. It is a
“newfound tracking capacity [that] runs against everyone . . . . [P]olice need not even
know in advance whether they want to follow a particular individual, or when. Whoever
the suspect turns out to be, he has effectively been tailed every moment of every day for
five years.” Carpenter, 585 U.S. at 312. Whereas past “attempts to reconstruct a person’s
movements were limited by a dearth of records and the frailties of recollection,” Location
History data allows the government to “travel back in time to retrace a person’s

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whereabouts, subject only to the retention polices of the wireless carriers.” Id. Google
retains Location History data indefinitely—even longer than the five-year period that the
carriers at issue in Carpenter maintained CSLI. See id.
Also like CSLI, Location History data can detail a log of a person’s movements over
several years. Critically, however, non-anonymous Location History data is far more
revealing than CSLI. Judge Wynn pointedly explains the differences. See opinion of
WYNN, J., at 45-46. Location History has the capacity to record a user’s location every
two minutes, or an average of 720 times per day. CSLI, in contrast, logged Carpenter’s
location an average of 101 times per day. Carpenter, 585 U.S. at 302. Location History
data is thus more “detailed” and “encyclopedic” than CSLI. Id. at 309. It is also far more
precise. Whereas CSLI places an individual “within a wedge-shaped sector ranging from
one-eighth to four square miles,” id. at 312, Location History can pinpoint an individual’s
location within three meters. Because non-anonymous Location History data is highly
revealing, the first Carpenter factor weighs in favor of Chatrie.
ii. Chatrie’s Disclosure of His Location History Data was not Sufficiently
Voluntary to Defeat His Reasonable Expectation of Privacy
Carpenter requires us to balance the revealing nature of non-anonymous Location
History data against a second consideration, the voluntariness with which it is disclosed to
Google. Whether the disclosure of data to a third party was “voluntary” is not a binary
inquiry but a matter of degree. Here, this factor does not tip decisively in favor of either
party. Though the Government describes Location History as a voluntary feature that a user
must “affirmatively enable,” J.A. 1337, the record shows that individuals may enable

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Location History without meaningfully consenting to data collection, or at least without
understanding the implications of the feature.
Google claims that Location History is disabled by default. Yet for those who
download certain Google apps—including popular apps such as Google Maps, Google
Photos, and Google Assistant—there is no “default” setting. Google repeatedly requires
users to make a choice. Through pop-up permission screens, users are asked either to grant
or deny Google permission to track their location.
Users need not intentionally seek to enable Location History. When a user opens
Google Maps for the first time, for example, a permission screen prompts the user to “Get
the most from Google Maps,” and states that “Google needs to periodically store your
location to improve route recommendations, search suggestions, and more.” J.A. 1485. A
button reading “YES I’M IN” is highlighted in blue, while the option to “SKIP” is not.
J.A. 1485. When an individual sets up an Android phone, like the phone used by Chatrie,
he is directed to use Google Assistant. Upon opening Google Assistant, he is presented
with a header instructing him: “Give your new Assistant permission to help you.”
J.A. 1980. Below that header, a prompt further instructs the user: “The Assistant depends
on these settings in order to work correctly. Turn on these settings.” J.A. 1980. One of
those settings is Location History. After scrolling, the user is given the options of “NO
THANKS” or “TURN ON.” J.A. 1124. By selecting “TURN ON,” the user enables
Location History. Here too, the “TURN ON” button is highlighted in blue, while “NO
THANKS” is not. J.A. 748–51.

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Google stated that approximately two-thirds of its “active users” have declined to
enable Location History, but this figure is misleading. One of Google’s experts testified
that “active Google users” includes anyone with a Google account on any device, including
a computer. That would include those who never downloaded a Google app and were thus
never presented with the choice of enabling Location History. Google does not claim that
two-thirds of its users, when confronted with a pop-up permission screen, selected “NO
THANKS” rather than “TURN ON.” Indeed, Google has provided no data about the
percentage of users who declined to enable Location History when prompted to do so.
Further, the fact that most Google users’ settings were different than Chatrie’s does not
suggest that he intentionally selected his particular settings, or that they intentionally
selected theirs.
Even after reviewing all available information about Location History provided by
Google, a user would struggle to determine where his Location History data is stored.
Google does not explicitly inform users whether Location History data is stored locally on
each phone, or whether it is stored on Google’s servers and accessible to Google
employees. Further, Google’s warnings do not indicate how many times a day Location
History data will be collected. The third-party doctrine concerns data that one “knowingly
share[s]” with a third party. Carpenter, 585 U.S. at 298. If users cannot determine what
kind of data is being collected in the first instance, the disclosure of this data cannot be
considered “knowing.”
Balancing the two Carpenter factors, (1) how much the data can reveal, and (2)
whether the data was disclosed voluntarily, I would conclude that the Government

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conducted a Fourth Amendment search when it obtained Chatrie’s non-anonymous
Location History data through its second and third requests to Google. Accordingly,
Chatrie held a reasonable expectation of privacy in this data, and obtaining it required a
valid warrant.
C. The Government’s Warrant Application Was Not Supported by Probable Cause
Upon concluding that the acquisition of Chatrie’s Location History data was a
Fourth Amendment search requiring a warrant, we must evaluate whether the geofence
warrant at issue was valid. Under the Fourth Amendment, a warrant “may not be issued
unless probable cause is properly established and the scope of the authorized search is set
out with particularity.” Kentucky v. King, 563 U.S. 452, 459 (2011).
The Government’s search, as effectuated through its second and third requests to
Google, was not supported by probable cause at the time the geofence warrant issued.
Probable cause must be evaluated at the time of the warrant application, not in light of
subsequent developments. See Smith v. Munday, 848 F.3d 248, 253 (4th Cir. 2017). When
the detective applied for the geofence warrant, it would have been impossible for him to
describe the facts that would ultimately support his decision to conduct a Fourth
Amendment search targeting nine particular individuals.
Before the first request to Google, the detective could make a single representation
about the Google users he would ultimately search: they would be among those near the
crime scene. That information unequivocally falls short of establishing probable cause. A
person’s mere proximity to suspected criminal activity “does not, without more, give rise
to probable cause to search that person.” Ybarra v. Illinois, 444 U.S. 85, 91 (1979). The

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government cannot, for example, search every unit in an apartment building because it has
probable cause to believe that some unknown part of the building holds evidence of a crime.
See Wayne R. LaFave, Search and Seizure: A Treatise on the Fourth Amendment § 4.5(b)
(6th ed. 2024); United States v. Clark, 638 F.3d 89, 95 (2d Cir. 2011); cf. Maryland v.
Garrison, 480 U.S. 79, 88 n.13 (1987). Instead, a warrant can authorize the search of all
persons in a particular place only if there is probable cause to believe every person in that
place was involved in or witnessed the criminal activity. Id. Here, of course, there was no
evidence that every individual in the vicinity of the bank around the time of the robbery
was involved in the crime. Nor was the purpose of the warrant to identify witnesses.
Unlike in Illinois v. Lidster, the purpose of the geofence search was to identify
suspects. 540 U.S. 419 (2004). The Government’s reliance on that case is unavailing. In
Lidster, the Court held that police did not violate the Fourth Amendment when, a week
after a hit-and-run, they set up a roadblock to briefly seize all motorists near the location
of the accident. 540 U.S. at 421–23. Those stops—executed without individualized
suspicion—were constitutional only because they were conducted to identify witnesses,
not suspects. Id. at 423. The Court described this as an “information-seeking kind of stop,”
emphasizing that “[t]he stop’s primary law enforcement purpose was not to determine
whether a vehicle’s occupants were committing a crime, but to ask vehicle occupants, as
members of the public, for their help in providing information about a crime in all
likelihood committed by others.” Id. at 423–24. The Court explained that “[t]he police
expected the information elicited to help them apprehend[ ] not the vehicle’s occupants,
but other individuals.” Id. at 423. In contrast, Indianapolis v. Edmond, 531 U.S. 32 (2000),

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established that a search or seizure conducted to “detect evidence of ordinary criminal
wrongdoing” rather than to seek information from witnesses is unconstitutional when the
government lacks individualized suspicion. Id. at 41.
In this case, the Government makes no claim that its “primary law enforcement
purpose” was identifying witnesses. The Government had already interviewed witnesses
at the time it applied for the Google warrant. The Government states that the purpose of
the warrant was to “was to obtain evidence to help identify and convict the robber and any
accomplices.” Gov’t Br. at 31. The warrant application itself focused on the fact that the
robber “had a cell phone in his right hand and appeared to be speaking with someone on
the device” immediately prior to the robbery. J.A. 112. As a result, the Government alleged
that “the requested data/information would have been captured by Google during the
requested time.” J.A. 112. Further, whereas law enforcement in Lidster sought “voluntary
cooperation” from potential witnesses, cooperation was not voluntary for potential
witnesses whose Location History data was disclosed without their knowledge in response
to the geofence warrant.
The Government’s reliance on Zurcher v. Stanford Daily is similarly misplaced. 436
U.S. 547 (1978). In Stanford Daily, as in this case, the government applied for a search
warrant without particular suspects in mind. Id. at 550–51. There, however, the government
did not ultimately search any individual. Rather, the government searched only the physical
office of the Stanford Daily, rifling through its photos and file cabinets. See id. at 551–54.
Though, as here, the government in Stanford Daily lacked probable cause to search any
individual, it did have reason to believe that evidence of a crime would be located in the

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office of the Stanford Daily. Id. at 551. As a result, the government had probable cause to
conduct the only search at issue: the search of the Stanford Daily’s office.
The critical distinction the Government misses is that here the search infringed on
the Fourth Amendment rights of Google users, including Chatrie, not Google. Through its
second and third requests to Google, the Government searched data belonging to nine
individuals whose Location History was stored in Google’s databases. The search at issue
in Stanford Daily is similar only to the Government’s first request to Google, as neither of
those undertakings violated any individual’s reasonable expectation of privacy. The fact
that the Government had probable cause to believe that evidence would be found
somewhere on Google’s servers did not, without more, provide probable cause to search
individual Google users’ accounts.
Analyzing Google’s anonymous data may have given the Government probable
cause subsequently to obtain a warrant for non-anonymous data. Had the detective gone to
a magistrate after analyzing the Google data he received in response to the first request, he
may have been able to articulate probable cause to search the Location History of particular
Google users, including Chatrie. The detective never went back to the magistrate, however.
He sought judicial authorization only once—prior to the first request to Google. Because
the detective could not explain why he would eventually search the Location History data
of certain, then-unknown users in Google’s dataset, he failed to show probable cause to
conduct the second and third requests. Under the terms of the geofence warrant, Google,
not a magistrate, was the sole entity that could confine the scope of the ultimate search.
Probable cause determinations cannot be delegated to private entities. Cf. Birchfield v.

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North Dakota, 579 U.S. 438, 469 (2016) (“Search warrants . . . ensure that a search is not
carried out unless a neutral magistrate makes an independent determination that there is
probable cause to believe that evidence will be found.” (emphasis added)); United States
v. Rubio, 727 F.2d 786, 794–95 (9th Cir. 1983).
D. Geofence Warrants are not Categorically Unconstitutional
In United States v. Smith, the Fifth Circuit held that a geofence warrant can never
be supported by particularized probable cause. 110 F.4th at 838. The Fifth Circuit
concluded that each request pursuant to Google’s three-step process, including the request
at step one, constitutes a Fourth Amendment search. In reaching this conclusion, the Fifth
Circuit focused on the mechanics of Google’s internal compliance processes:
Step 1 forces the company to search through its entire database to provide a
new dataset that is derived from its entire Sensorvault. In other words, [the
Government] cannot obtain its requested location data unless Google
searches through the entirety of its Sensorvault—all 592 million individual
accounts—for all of their locations at a given point in time.
Id. at 837. The Fifth Circuit reasoned that “these geofence warrants fail at Step 1—they
allow the Government to rummage through troves of location data from hundreds of
millions of Google users.” Id. at 837–38.
As Judge Richardson correctly points out, the “592 million” number is a red herring.
See opinion of RICHARDSON, J., at 80 n.17. The government does not search every user
in Google’s dataset each time it requests Location History data. A search can occur only
when the government accesses the requested information, not when a company begins
looking through its internal database. See Beautiful Struggle, 2 F.4th at 344 (“Carpenter
was clear on that issue: a search took place ‘when the Government accessed CSLI from

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the wireless carriers.’” (emphasis in original) (quoting Carpenter, 585 U.S. at 313)). The
proper focus of our inquiry is the data the government obtains, not the size of Google’s
database. Though the Fifth Circuit refers to this proposition as “breathtaking,” Smith, 110
F.4th at 838 n.12, any other approach would be nonsensical. The scope of a search does
not depend on what a company’s compliance officer incidentally encounters—but never
discloses to law enforcement—while looking through the company’s database to fulfill a
particular request. In Carpenter, for example, the duration of the search would not have
changed had Sprint stored the requested CSLI in a spreadsheet that contained additional
days of CSLI data. Because the detective’s first request did not amount to a search of any
individual in Google’s database, the Fourth Amendment did not require the detective to
establish probable cause before submitting that request.5
If requests for Google’s step-one data constitute Fourth Amendment searches of
individuals—thus requiring a warrant—such warrants could not be supported by probable
cause in most instances. Obtaining a warrant would require probable cause to search all
individuals who fall within a particular geofence. The government would thus need to show
probable cause that every individual near the scene of a crime was involved in the crime or
witnessed it. Because the government is unlikely to be able to make such a showing in most
5 Even if the initial geofence request was not a Fourth Amendment search, the Stored
Communications Act may independently require the government to obtain a warrant before
requesting Location History data. See 18 U.S.C. § 2703. The Act states that the government
must obtain a warrant before compelling an Internet service provider to disclose the
“contents” of electronic communications, such as the text of an email. Id. § 2703(a),
(b)(1)(A). At oral argument, the Government conceded that Location History data is likely
“content” within the meaning of the Act. See Oral Argument at 1:11:40–1:11:52. Because
Chatrie waived any statutory claim, however, we need not reach this issue here.

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cases, it would ordinarily be prevented from obtaining geofence warrants altogether.
III. Conclusion
Though this case involves advanced technology and difficult legal questions,
complexity does not absolve us of our obligation to interpret the Constitution. I see little
benefit in postponing these issues until another day. Deciding this case without reaching
the Fourth Amendment issues merely perpetuates the constitutional fog that will allow
unlawful searches of Location History data to continue to evade consequence through the
good-faith exception.
In my view, the government conducts a Fourth Amendment search when it obtains
non-anonymous Location History data. This includes pseudonymous data that is likely to
be traceable to a particular individual. Therefore, I would find that the Government
conducted a search of Chatrie through its second and third requests to Google. Because the
Government relied on a warrant that was not supported by probable cause, its search of
Chatrie violated the Fourth Amendment.

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GREGORY, Circuit Judge, dissenting:
The Fourth Amendment exists to protect “‘the privacies of life’ against ‘arbitrary
power,’” Carpenter v. United States, 585 U.S. 296, 305 (2018) (quoting Boyd v. United
States, 116 U.S. 616, 630 (1886)), and requires that law enforcement obtain a warrant prior
to conducting a search, id. at 304 (citing Smith v. Maryland, 442 U.S. 735, 740 (1979)). In
no uncertain terms, it states that “no Warrants shall issue, but upon probable cause,
supported by Oath or affirmation, and particularly describing the place to be searched, and
the persons or things to be seized.” U.S. Const. amend. IV.
When officers violate these principles, the exclusionary rule, created by the
Supreme Court to safeguard against Fourth Amendment violations, generally prohibits use
of illegally obtained evidence to prove the defendant’s guilt at trial. United States v.
Stephens, 764 F.3d 327, 335 (4th Cir. 2014) (collecting cases). However, the exclusionary
rule is not a “strict-liability regime,” Davis v. United States, 564 U.S. 229, 240 (2011), and
only applies where its application will “deter future Fourth Amendment violations,” id. at
236–37; see also Stephens, 764 F.3d at 335; Illinois v. Krull, 480 U.S. 340, 347 (1987).
Where an officer reasonably relies on a warrant later determined to lack probable cause,
the good faith exception permits admission of the evidence despite the constitutional
violation. United States v. Leon, 468 U.S. 897, 918–21 (1984). Whether evidence should
be excluded or admitted following a Fourth Amendment violation requires us to assess if
“a reasonably well[-]trained officer would have known that the search was illegal in light
of all of the circumstances.” Herring v. United States, 555 U.S. 135, 145 (2009) (internal
quotation marks omitted).

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To consider these important questions––whether there is a Fourth Amendment
violation, and whether the Leon good faith exception should apply––requires courts to
examine the underlying warrant and the circumstances pertaining to its issuance and
execution. That task will sometimes require courts to wade through murky constitutional
and doctrinal waters to provide necessary guidance to district courts, attorneys, law
enforcement, and citizens alike. But our Court has decided not to do so here, opting instead
to sidestep the complex issues presented in this case. The majority of this Court has
decided to affirm the district court’s opinion, but its reasoning is fractured.
I concur largely in the writings of Judge Wynn and Judge Berner in finding that
there was a constitutional violation, as I believe that the geofence warrant at issue glaringly
infringed on the Fourth Amendment. However, I write separately to explain why I believe
the good faith exception is inapplicable in this case.
I.
Google account users can opt in to location history on their mobile devices, which
allows users to keep track of locations they have visited. J.A. 127. At the time of the
offense, Google processed and stored this location history if users shared it via location
reporting. J.A. 125, 129–30. Pursuant to the Stored Communications Act, 18 U.S.C.
§§ 2701 et seq., law enforcement can obtain legal process compelling Google to disclose
location information, including through geofence warrants. J.A. 124–25. In conjunction
with the Department of Justice, Google developed a three-step anonymization and
narrowing protocol in response to these geofence requests. J.A. 1344.

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In this case, Detective Hylton swore an affidavit for a geofence warrant for Google
users’ location history. J.A. 107. The warrant, at Step One, authorized a search for
anonymized data of Google users with shared location history for a limited time frame (one
hour) and a small geographic scope (150-meter radius) where the crime occurred. See J.A.
107, 110–11. At Step Two, it authorized a search expanded in both time (one more hour
in total) and geographic scope (completely unbounded) and narrowed to a subset of users.
J.A. 110–11, 135–36.1 And at Step Three, the search included non-anonymized,
identifying information for a smaller subset. J.A. 111.
Significantly, the warrant did not explain how law enforcement would narrow the
list of users at Steps Two and Three based on the information obtained at Step One. See
J.A. 110–11. Even now, the government cannot tell us what justified the more intrusive
searches at Steps Two and Three, or how or why there was probable cause to search those
individuals. See e.g., Oral Argument at 57:17, 1:10:11. Instead, the warrant gave law
enforcement broad discretion to request and obtain a seemingly unlimited amount of data
associated with devices identified at Step One, checked only by Google.
At Step One, Google provided anonymized data for nineteen devices located within
the geofence—which included homes, a hotel, a large church, and a restaurant—thirty
minutes before and after the robbery. J.A. 1354, 1357. At Step Two, Detective Hylton
1 Chatrie argues that the data provided at Step Two could be considered non-
anonymized, as an expert could identify each of the nine users based on the data provided,
such as where they traveled during the expanded location and time. Oral Argument at
1:37:48, United States v. Okello Chatrie, (4th Cir. 2025) (No. 22-4489),
https://www.ca4.uscourts.gov/OAarchive/mp3/22-4489-20250130.mp3 (henceforth “Oral
Argument).

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ultimately identified nine devices and requested additional location data for those devices
expanded for thirty minutes before and thirty minutes after the one-hour window authorized
at Step One, and without any geographic limitations. J.A. 1355. This production allowed
Detective Hylton to track those devices outside of the confines of the geofence for an hour
before and after the crime was committed. At Step Three, Detective Hylton requested, and
Google provided identifying information about the accounts associated with three of the
devices identified at Step Two. J.A. 1355–56. Consequently, the warrant permitted
Detective Hylton to obtain information that the Constitution forbids without probable
cause—the detailed movements of anyone with a device identified at Step One—without
any additional judiciary oversight. Such lack of additional judiciary oversight was an error
by the magistrate.
But that is not enough. As we know from Leon, the magistrate’s errors alone are
insufficient to warrant suppression of evidence obtained pursuant to a deficient warrant.
This is because magistrates are “neutral judicial officers” who have “no stake in the
outcome of particular criminal prosecutions.” Leon, 468 U.S. at 917. As such, excluding
evidence because of a magistrate’s error would not deter similar misconduct and may even
discourage an officer in the future. Id. at 920 (stating that excluding evidence obtained
following an officer’s objectively reasonable reliance on a search warrant would “in no
way affect his future conduct unless it is to make him less willing to do his duty.”) (citation
and quotation marks omitted).
“Deference to the magistrate, however, is not boundless.” Id. at 914. Reliance on the
warrant alone is therefore insufficient to protect against exclusion of the recovered evidence.

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Such is the case where the warrant is “so facially deficient—i.e., in failing to particularize the
place to be searched or the things to be seized—that the executing officers cannot reasonably
presume it to be valid.” Id. at 923. The good faith exception also does not apply where the
facts indicate that the investigating officer “could not have harbored an objectively reasonable
belief in the existence of probable cause.” Id. at 926. As one of my colleagues concluded in
assessing the Fourth Amendment violation in this case, see Berner, J., concurring at 109–13
the warrant in this case lacked probable cause. As I will now explain further, the evidence in
this case should have been excluded, as “it is clear that . . . the officer [had] no reasonable
grounds for believing that the warrant was properly issued.” Leon, 468 U.S. at 922–23.
To begin, neither the affidavit nor the warrant explained how law enforcement
would conduct its review between the various steps of Google’s process. J.A. 107, 110–
11. Nevertheless, the warrant authorized Detective Hylton to obtain information at Step
Three that was of the most personal nature—account-identifying information—for any
account associated with a device he identified from Step One without probable cause for
each individual’s data. But for what amounted to a general warrant, Detective Hylton
would not have otherwise received such information.
Additionally, Detective Hylton had unbridled discretion to determine who would be
subject to intrusive and expansive searches. For example, at Step Two, Detective Hylton
initially requested additional location data for all nineteen users identified at Step One,
expanded for thirty minutes before and thirty minutes after the originally requested one
hour window, and without any geographic limitations. J.A. 1354–55; see also J.A. 98. His
email to Google stated that he was requesting the additional data “in an effort to rule out

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possible co-conspirators,” and that nine of the users “may fit the more likely profile of
parties involved.” J.A. 98. At oral argument, the government contended that it was looking
for witnesses as well. See Oral Argument at 53:51. Detective Hylton followed up on his
email twice on the two following days. J.A. 100, 1059. He then left two voicemails for a
Google specialist; the specialist returned his call and recounted the issues in Detective
Hylton’s email, describing how his request did not follow the three-step process and
explaining the importance of narrowing his request. J.A. 102, 1584–85. The next day,
Detective Hylton sent an email narrowing his request to nine users. J.A. 102, 1059, 1584.
Google provided Detective Hylton the anonymized, expanded data for nine users. J.A.
1585. As was explained before, the government cannot explain how or why Detective
Hylton narrowed in on the particular users. And at no point during this process did
Detective Hylton seek judicial intervention, although the warrant did not contain sufficient
probable cause and particularity to authorize these additional searches.
Detective Hylton could not have reasonably believed that the liberty authorized by
the warrant was constitutional given the lack of specificity the Fourth Amendment
explicitly demands.2 United States v. Groh, 540 U.S. 551, 563 (2004) (citing Harlow v.
Fitzgerald, 457 U.S. 800, 818–19 (1982)) (“Given that the particularity requirement is set
forth in the test of the Constitution, no reasonable officer could believe that a warrant that
2 See, e.g., Groh v. Ramirez, 540 U.S. 551 (2004) (declining to extend the Leon good
faith exception to law enforcement officials who issued a warrant that listed only the
location of the evidence without describing the items to be seized); United States v. George,
975 F.2d 72 (2d Cir. 1992) (declining to extend the good faith exception to a warrant issued
following a robbery that included only a list of items, the address subject to search, and the
phrase “any other evidence relating to the commission of a crime).

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plainly did not comply with that requirement was valid.”). On its face, the warrant lacked
the requisite constitutional requirements to conduct increasingly intrusive searches at Steps
Two and Three of Google’s process. Instead, the warrant ceded authority and decision-
making from an independent judicial officer to a private corporation. No reasonable officer
could believe that execution of this geofence warrant in this manner comports with the
Fourth Amendment and the liberties it serves to protect. In the same way that this cannot
cure the constitutional violation that occurred, see Wynn, J. concurring at 35–53 and
Berner, J., concurring at 109–13, it does not excuse the officer’s indiscretions. Exclusion
of the evidence is therefore appropriate here.
One dear colleague suggests that even if there was a search, placing restraints on
law enforcement’s use of geofence location data and other emerging technologies is
unjustified. Wilkinson, J., concurring at 22–23 (stating “[e]ven if there was a search, there
is no room for emergent judicial hostility” because such restraint would “frustrate law
enforcement’s ability to keep pace with tech-savvy criminals” and “[m]ore cold cases
would go unsolved”). I am not unmindful of nor insensitive to the number of cases that go
unsolved each year and the lack of closure that results from this unfortunate reality. I am,
however, vehemently opposed to the notion that new technology erodes the protections and
principles of our Constitution. Crimes have gone unsolved due to lack of suspect and
witness identification, lack of evidence, and other issues beyond law enforcement control
presumably since the beginning of recorded time.
That fact, however, has never justified infringement on the Constitution and as such,
should not be used as a reason to withhold Fourth Amendment protections or excuse Fourth

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Amendment violations. Indeed, the Supreme Court has said as much. Specifically, the
Supreme Court stated “that [t]he efforts of the courts and their officials to bring the guilty
to punishment, praiseworthy as they are, are not to be aided by the sacrifice of those great
[constitutional] principles.” Mapp v. Ohio, 367 U.S. 643, 648 (1961) (quoting Weeks v.
United States, 232 U.S. 383, 391–92 (1914)). Simply put, the judiciary may not be a safe
harbor to violations of the Fourth Amendment because cold cases—which have always
been an unfortunate reality—will continue. This must remain true no matter how well-
meaning the investigative officers’ intentions. And technological developments nor
corporate practices should alter that calculus.
Some of my colleagues suggest that exclusion is not warranted in this case because
this Court nor any other court had opined on the validity of geofence warrants at the time
of Detective Hylton’s application. Thus, they suggest that any error on Detective Hylton’s
part resulted from the lack of clear direction regarding geofence warrants. But, contrary to
that suggestion, an officer need not know the judiciary’s view on the use of new technology
with the Fourth Amendment to know that the information in the warrant was insufficient.
It is well-settled that, to be valid, a warrant must include the particular person, place, or
thing to be searched. Smith, 442 U.S. at 736 n.2 (citing U.S. Const. amend. IV).
Accordingly, whatever the alleged uncertainty regarding geofence warrants, it was not
unclear what the Constitution demands of all warrants. That being the case, the lack of
authority regarding geofence warrants does not end the inquiry into the objective
reasonableness of Detective Hylton’s conduct. And for good reason, as endorsement of
that practice would run the risk of forgiving law enforcement impropriety simply because

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no court has specifically forbidden it. That is the very type of behavior the Supreme Court
cautioned against in the context of retroactivity of Fourth Amendment rulings. Namely,
that “police or other courts [would] disregard the plain purport of our decisions and [] adopt
a let’s-wait-until-it’s-decided approach.” Leon, 468 U.S. at 912 n.9 (citing U.S. v. Johnson,
457 U.S. 537, 561 (1982)) (internal quotation marks omitted). If we permitted that course
of action, Fourth Amendment protections would become a nullity in the face of rapidly
emerging technology.
The same unfortunate fate would result if Detective Hylton’s belief in his actions
was dispositive. Leon instructs us to assess whether the investigating officer held an
objectively reasonable belief in the warrant’s validity and his actions. 468 U.S. at 919.
Detective Hylton’s subjective belief, or what he “could have” believed, then, is therefore
of little moment. Contra Heytens, J., concurring at 88 (stating “because the investigating
officer could have had ‘an objectively reasonable good-faith belief that his conduct was
lawful,’ I think the district court was right to withhold ‘the harsh sanction of exclusion’”)
(citing Davis, 564 U.S. at 238, 240) (emphasis added) (internal brackets omitted).
This too makes sense as constitutional rights should not be so subjugated to the will
of individual officers. Leon, 468 U.S. at 915 n.13 (“Good faith on the part of the arresting
officers is not enough”) (citing Henry v. United States, 361 U.S. 98, 102 (1959)) (internal
brackets and quotation marks omitted). If subjective good faith alone were the test, the
protections of the Fourth Amendment would evaporate, and the people would be “‘secure
in their persons, houses, papers, and effects,’ only in the discretion of the police.” Id.

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Similarly, it is a perilous day when our Fourth Amendment protections lie in the
hands of a private company, and constitutional rights should not and cannot be defined by
the internal policies of a private corporation. This is so even where the process was created
with input from law enforcement. To that point, I note that the government and some of
my colleagues highlight that Google’s process was created in conjunction with the
Department of Justice. Notably, the government’s interest in defining the Fourth
Amendment right is no greater than that of the defense counsel, other attorneys, and the
public at large—none of whom were offered a seat at the table. And, even if Google had
opened the forum to all potential stakeholders, its process would still lack finality because
corporations lack the authority to interpret the Constitution. That responsibility belongs to
the courts, and we must not relinquish it to those not charged with protecting the
Constitution or otherwise abdicate it because the task seems too difficult.
II.
Law enforcement should not be denied the benefit of the efficiencies that emerging
technologies offer. However, when seeking digital evidence, officers must demonstrate at
least the same level of supporting information necessary to justify the search of physical
places and things. In other words, officers should not be permitted, with aid of an unbridled
warrant, to shake the proverbial digital tree without an objectively reasonable belief that
the warrant and the manner of its execution are consistent with the Fourth Amendment.
And that reasonable belief must be founded on something more than the commonality of

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the technology at issue in the case. This is especially so given that technology has and
continues to shift our understanding of “person, place, or thing.”
Some cry “novelty” and “technological change” as an excuse for a fundamental
departure from our constitutional principles. But one thing is for certain: technology will
continue to shift, but the basic protections of the Fourth Amendment must remain. The
people’s rights against unreasonable searches and seizures cannot not bend to
accommodate the volatility of technology. Rather, new technologies must bend to
accomplish the vitality of the protections guaranteed to the people under the Fourth
Amendment. Regrettably, the ever-increasing extension of the good faith exception to the
exclusionary rule has turned this sacred principle of Fourth Amendment interpretation on
its head.
The Constitution nor Fourth Amendment precedent to date anticipated that person
may one day refer to a non-human, such as Optimus; places could encompass locations in
the Metaverse (or otherwise only digitally accessible); and things could include intangible
objects that exist only electronically. Given that reality, the judiciary still must fulfill its
role and duty to ensure that the interpretation of the Constitution does not fall solely in the
hands of anyone not charged with protecting the rights it guarantees. Our Court failed to
do so here. Thus, I must dissent.

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