In re: Nissan North America, Inc. Litigation. Robert Garneau v. Nissan North America, Inc.; Nissan Motor Company, Ltd.

RECOMMENDED FOR PUBLICATION
Pursuant to Sixth Circuit I.O.P. 32.1(b)
File Name: 24a0260p.06
UNITED STATES COURT OF APPEALS
FOR THE SIXTH CIRCUIT
IN RE: NISSAN NORTH AMERICA, INC. LITIGATION.
___________________________________________
ROBERT GARNEAU; NANCY HOUSELL; JEFFREY
OLKOWSKI; VAUGHN KERKORIAN; DAVID TURNER;
COURTNEY JOHNSON; SCOTT REEVES; LISA
HENDRICKSON; RHONDA PERRY; JANE REEVES;
MORELA JOVA; KIMBERLY WRIGHT; TODD BURROWS;
HOSEA BARTLETT; AURELIA FOWLER; JOHN
HARTWELL; KEITH HUDDLESTON; LAKEITA KEMP;
MICHELLE BEREDA; ANGELENE HOEFFKEN; SCOTT
NERI,
Plaintiffs-Appellees,
v.
NISSAN NORTH AMERICA, INC.; NISSAN MOTOR
COMPANY, LTD.,
Defendants-Appellants.
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No. 23-5950
Appeal from the United States District Court for the Middle District of Tennessee at Nashville.
Nos. 3:19-cv-00843; 3:19-cv-00854; 3:22-cv-00098;
William Lynn Campbell, Jr., District Judge.
Argued: October 31, 2024
Decided and Filed: November 22, 2024
Before: SUTTON, Chief Judge; LARSEN and MURPHY, Circuit Judges.
_________________
COUNSEL
ARGUED: Aaron D. Van Oort, FAEGRE DRINKER BIDDLE & REATH LLP, Minneapolis,
Minnesota, for Appellants. John E. Tangren, DICELLO LEVITT LLC, Chicago, Illinois, for
Appellees. ON BRIEF: Aaron D. Van Oort, John L. Rockenbach, Anderson C. Tuggle,
FAEGRE DRINKER BIDDLE & REATH LLP, Minneapolis, Minnesota, E. Paul Cauley, Jr.,
>

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S. Vance Wittie, FAEGRE DRINKER BIDDLE & REATH LLP, Dallas, Texas, for Appellants.
John E. Tangren, Adam J. Levitt, Daniel R. Ferri, Adam Prom, DICELLO LEVITT LLC,
Chicago, Illinois, J. Gerard Stranch, IV, Michael C. Iadevaia, STRANCH, JENNINGS &
GARVEY, PLLC, Nashville, Tennessee, Benjamin L. Bailey, Jonathan D. Boggs, BAILEY &
GLASSER LLP, Charleston, West Virginia, W. Daniel “Dee” Miles, III, BEASLEY, ALLEN,
CROW, METHVIN, PORTIS & MILES, P.C., Montgomery, Alabama, Joel D. Smith, SMITH
KRIVOSHEY, P.C., Boston, Massachusetts, for Appellees. Philip S. Goldberg, SHOOK,
HARDY & BACON L.L.P., Washington, D.C., John M. Thomas, DYKEMA GOSSETT PLLC,
Ann Arbor, Michigan, Kyle M. Asher, DYKEMA GOSSETT PLLC, Lansing, Michigan, Donald
M. Falk, SCHAERR ǀ JAFFE LLP, San Francisco, California, Jeffrey R. White, AMERCAN
ASSOCIATION FOR JUSTICE, Washington, D.C., for Amici Curiae.
_________________
OPINION
_________________
SUTTON, Chief Judge. Many modern cars, indeed more and more each year, provide
automatic alerts when they come too close to another car or an obstacle and will automatically
brake to avoid a collision. Some models of Nissan cars, according to the complaint in this case,
occasionally activate these alerts at the wrong time, say at a railroad crossing or in a parking
garage. A group of car owners sued Nissan for various state-law claims. The district court
certified ten statewide classes under Civil Rule 23(b)(3). Because the classes do not meet the
material requirements for certification, we vacate and remand for further proceedings.
I.
In 2016, Nissan began equipping its cars with automatic electronic braking systems.
Each system has three components: a radar, a control unit, and the brakes. The radar measures
the distance to and speed of nearby obstacles and notifies the control unit, which interprets the
data. If the data suggest a potential collision, the control unit issues a visual and audible warning
to the driver. If the driver brakes, the system helps him by increasing the braking force. If he
does not, the control unit alerts the driver again and may brake automatically. The control unit
brakes harder as the risk of a crash becomes imminent.
Some parameters constrain the system. The control unit limits heavy braking at speeds
above 25 miles per hour for safety reasons. It also stops automatic braking if the driver steers, if

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the driver accelerates, or if the obstacle moves. Drivers may deactivate the automatic braking
system at any time.
Fourteen Nissan models at issue here use the ARS410 model radar: the 2017–20 Rogue;
the 2017–21 Rogue Sport; the 2019–21 Altima; and the 2020–21 Kicks.
In 2017, some drivers reported “phantom activations” of the automatic braking system at
low overpasses, railroad crossings, and parking garages. R.243-37 at 2; R.263-8 at 8; R.263-11
at 9. Engineers deduced that the radar hardware sometimes misread the road ahead when drivers
approached an incline or turned on a curve. On a curve, the radar might treat a car in the
adjacent lane as an obstacle directly ahead. If driving uphill in, say, a multi-tiered parking
garage, the radar might perceive a low-hanging overpass as an incoming wall.
Bound by hardware limitations, Nissan turned to software solutions. In 2018, it released
the “S1” update to both the radar’s software and the control unit’s software, notifying dealers and
owners of the available modification. In 2019, Nissan released the “S2” software update to the
radar and control unit to refine target recognition in parking garages. By August 2022, around
63% of ARS410 radar-equipped Rogue, Rogue Sport, Altima, and Kicks owners had upgraded to
the S2 software.
In June 2020, individuals from ten states—California, Connecticut, Florida, Illinois,
Massachusetts, Missouri, New York, Ohio, Pennsylvania, and Texas—sued Nissan, alleging that
it had sold them defective cars because they contained faulty automatic braking systems. They
argued that the defects breached their warranties, constituted fraud, violated their states’
consumer protection statutes, and unjustly enriched Nissan. The plaintiffs moved to certify ten
statewide classes of owners or lessees of the fourteen models with this radar.
Two perspectives emerged before the district court. From the plaintiffs’ vantage point, a
single radar problem plagues each Nissan car and lies at the center of each state-law claim.
Nissan acknowledged that an incorrect prompt from the radar could pose a safety hazard. And
the plaintiffs presented the expert report of Steve Loudon, a control systems engineer who
identified the radars as the “root cause” of the phantom brake activations. R.241 at 4. The class
action process, as they see it, could quickly confirm or deny the alleged malfunction.

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From Nissan’s vantage point, this case involves dozens of distinct products and many
versions of those products—and at any rate does not concern one product liability tort action
about one alleged defect but dozens of distinct consumer claims, including claims for express
warranty, implied warranty, fraudulent concealment, consumer protection, and unjust
enrichment. It produced the expert report of Dr. Nathan Soderborg, a statistician who observed
that brake-related warranty claim rates varied widely across vehicle model and software update
level. Owners of newer models were significantly less likely to seek repairs for their vehicles,
which indicated that different claimants experienced different defects based on different
combinations of vehicle models and software versions. Because some of the plaintiffs purchased
their vehicles before the release of later model versions and updates, Nissan’s knowledge of
these defects would vary depending on when each claimant purchased the vehicle. And because
the case did not involve one product liability claim but a range of warranty, fraud, and consumer
claims, each with distinct individualized elements, it did not lend itself to the types of common
questions and answers that Rule 23 was designed to facilitate. As for the plaintiffs’ expert,
Loudon, Nissan thought that he lacked the qualifications to opine on automated braking systems
and could not “identify any particular defect” anyway. R.264 at 30.
The district court agreed with the plaintiffs and certified all ten classes. A motions panel
of this Court granted Nissan’s petition for interlocutory appeal under Rule 23(f). In re Nissan N.
Am., Inc., No. 23-0501 (6th Cir. Oct. 24, 2024).
II.
Did the district court properly certify these ten classes? Abuse-of-discretion review
applies to the court’s decision. In re Whirlpool Corp. Front-Loading Washer Prods. Liab. Litig.,
722 F.3d 838, 850 (6th Cir. 2013). A court abuses that discretion if it relies on clearly erroneous
facts, misapprehends the law, or makes a “clear error of judgment.” In re Ford Motor Co.,
86 F.4th 723, 727 (6th Cir. 2023) (per curiam).
Because class certification “magnifies the stakes of litigation” by resolving hundreds, if
not thousands, of cases at one time, Civil Rule 23 imposes stringent requirements on the process.
Id. at 726; Wal-Mart v. Dukes, 564 U.S. 338, 349 (2011). The named claimants must

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“affirmatively demonstrate” the four threshold imperatives of certification. Dukes, 564 U.S. at
350. The class must be sufficiently “numerous” that joinder is unrealistic. Fed. R. Civ.
P. 23(a)(1). The combined claims must raise “common” questions of law or fact. Fed. R. Civ.
P. 23(a)(2). The class representative’s claims must be “typical” of the claims of other members
in the class. Fed. R. Civ. P. 23(a)(3). And the named representative must be in a position to
“fairly and adequately” look after the interests of the other class members. Fed. R. Civ.
P. 23(a)(4). After that, the plaintiff must satisfy the requirements of one of the types of class
actions permitted under Rule 23(b): actions where separate lawsuits would risk inconsistent
verdicts or impede third-party interests ((b)(1)), actions where injunctive or declaratory relief is
appropriate ((b)(2)), and, the one at issue here, actions where common questions predominate
over issues affecting individual plaintiffs ((b)(3)). Pilgrim v. Univ. Health Card, LLC, 660 F.3d
943, 945–46 (6th Cir. 2011).
Plaintiffs “must actually prove—not simply plead—that their proposed class satisfies
each requirement.” Halliburton Co. v. Erica P. John Fund, Inc., 573 U.S. 258, 275 (2014). In
assessing this proof, the district court must conduct a “rigorous analysis” to determine whether
the plaintiff has met each of these requirements. Dukes, 564 U.S. at 351–52; Comcast Corp. v.
Behrend, 569 U.S. 27, 33 (2013). A district court abuses its discretion by failing to do so. Ford,
86 F.4th at 727.
As this interlocutory appeal comes to us, it raises three questions. Did the district court
properly identify a common question of law or fact under Rule 23(a)(1)? Did the court properly
determine that common questions predominate over individual ones under Rule 23(b)(3)? Did
the court properly rely on the plaintiffs’ expert in granting class certification without ensuring
that he was qualified under Daubert to offer his report? Each question deserves a turn.
A. Common Questions of Law or Fact
Civil Rule 23(a) requires the plaintiff to identify “questions of law or fact common to the
class.” In asking whether the trial court conducted a “rigorous analysis” of commonality, Dukes,
564 U.S. at 351, the answer does not turn on whether the district court wrote a long opinion or
held multiple hearings. It turns on whether the court examined the material elements of each

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claim and determined which ones, if any, yield a common answer. Else, how could a court know
precisely which common factual questions—which elements of the cause of action—it could
submit to the jury? And how else could it know whether any common questions predominate
over any individualized questions? Commonality drives the initial Rule 23 inquiry. It either
establishes the first building block of a proposed class action or exposes an inadequate
foundation.
The claimant at a minimum must show that the action will “resolve an issue that is central
to the validity of each one of the claims.” Dukes, 563 U.S. at 350. A factual issue will not be
“central” to an aggregate dispute if it does not “affect at least one element” of the joined claims.
Doster v. Kendall, 54 F.4th 398, 430 (6th Cir. 2022) (quotation omitted), judgment vacated on
other grounds, 144 S. Ct. 481 (2023). The district court thus must walk through each cause of
action, identify the relevant elements, and evaluate which elements, if any, submit to common
answers. To be common, the question must “allow a decisionmaker to reach a yes-or-no answer
for the class in ‘one stroke.’” Id. at 430–31 (quotation omitted). If the court can answer “yes”
for some class members and “no” for others, no commonality exists. Id. at 431. So too if
different class members must use different pieces of evidence to answer the question. Tyson
Foods, Inc. v. Bouaphakeo, 577 U.S. 442, 453 (2016). To identify such variances, a careful
analysis of commonality must assess potential “[d]issimilarities within the proposed class” and
explain why these apparent differences do not defeat class certification. Dukes, 564 U.S. at 350
(quotation omitted). The court must consider opposing arguments to ensure that the plaintiffs
“actually prove” a common answer exists. Halliburton, 578 U.S. at 275; Ford, 86 F.4th at 728.
Our decision in Doster shows how one imperative of this analysis works—that the trial
court must examine the elements of the relevant claims to determine whether they yield yes-or-
no answers. 54 F.4th at 430–31. In that case, service members alleged that the Air Force
systematically denied their applications for religious exemptions from COVID-19 vaccine
mandates, violating the Religious Freedom Restoration Act of 1993 and the Free Exercise
Clause. Id. at 405. We held that two common questions existed for these pattern-or-practice
claims: whether the Air Force followed a policy of rejecting religious exemptions and whether it
treated religious exemptions worse than other exemptions. Id. at 433. We noted that both

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questions directly answered central elements of the pattern-or-practice claims. The first question
would inform whether the Air Force took the “least restrictive means” to achieve its public-
health interests under the statute. Id. at 433–34 (quotation omitted). The second question would
answer whether the Air Force’s policy was “neutral and generally applicable” under the First
Amendment. Id. at 434; see also Dukes, 564 U.S. at 349–50 (assessing the elements of an
employment discrimination claim to determine whether the proposed class action would yield
common yes-or-no answers); Whirlpool, 722 F.3d at 853–54 (assessing the elements of a breach-
of-warranty claim to determine whether the proposed class action would yield common yes-or-
no answers).
Ford shows how another imperative of this analysis works and does so in the context of a
product-liability case—that the yes-or-no inquiry must apply to materially similar car models.
Owners of Ford F-150 pickup trucks alleged that their trucks contained faulty brake cylinders.
Ford, 86 F.4th at 727. Ford contended that “key changes” to brake units over the years remedied
those defects in some of the model years. Id. at 728. That suggested that some plaintiffs drove
cars without a common defect. Id. The district court disregarded those changes because the
claims were “based on the same Brake System Defect across all Class Vehicles.” Id. In
rejecting this explanation, we reasoned that Rule 23 demands that the district court grapple with
evidence of material changes to the allegedly defective product. Id. at 727–28. Only by coming
to grips with changes to the challenged component of the car could the court decide whether any
central questions “can each be answered in one stroke.” Id. at 727 (quotation omitted). By
failing to do so, the trial court did not give the defect’s alleged commonality the scrutiny
required. Id. at 728.
In applying these requirements to this class-certification order, we see two over-arching
flaws. One turns on the distinct software upgrades created for different model cars. The other
turns on the failure to analyze the elements of each state law claim to determine which, if any,
elements would yield common yes-or-no answers. In fairness to the district court, it did not have
the benefit of our Ford decision at the time it certified these classes.
Software upgrades for different models. All ten classes of Nissan buyers allege that their
cars contain the same problematic automatic braking systems based on the same faulty radar.

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Even if we assume for the sake of argument that one “defect” links all of these claims (more on
that later), software updates to the system radar and control units remedied those alleged flaws in
some cars. The district court must grapple with those updates to answer whether the existence of
a defect can be established in one stroke. Id. at 727.
That same problem infiltrates the other possibilities for commonality. We cannot
determine whether common evidence establishes Nissan’s knowledge as to the defects if the
software updates remedied those defects for some cars. Id. at 728. Nor can we determine
whether, for each state class, a common question of liability exists for all claims. The plaintiffs’
argument reduces to the bare assertion that common evidence establishes each cause of action.
But without a common defect, that cannot be the case.
The district court did not consider evidence about these differences because it viewed
them as rooted in a “level of specificity” not required at the certification stage. R.306 at 7. But
Rule 23(a)(1) does not discount product differences based on their specificity. It asks only
whether generalized evidence can resolve common questions “in one stroke.” Ford, 86 F.4th at
727 (quotation omitted). Assessing the materiality of these differences is critical to analyzing
whether these questions will yield common answers, even if that analysis requires specificity in
some circumstances.
Element-by-element assessment of commonality. The lack of a common answer to this
threshold factual question—which version of the software was included in the car each consumer
drove?—alone justifies vacating this order under Ford. But on remand, the district court must do
more than identify whether the plaintiffs’ questions have some common answers. That’s because
not every question with a common answer meets Civil Rule 23(a). It’s only “central” issues that
matter. Dukes, 564 U.S. at 350. Otherwise, frivolous inquiries such as whether everyone sued
the same company would suffice. Id. at 349–50.
The only way to determine whether an issue is central is to deal with the material
elements of each claim. Doster, 54 F.4th at 430. The district court must examine each cause of
action, identify the relevant elements, and evaluate how the common answer at hand helps to

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resolve at least one of them. And it must repeat this analysis for all ten classes. That is the only
way to assess whether the proposed class questions can resolve each claim in each class.
In an element-by-element analysis of each state claim, notably, it does not suffice simply
to allege a common “defect” in a car—whether, in the plaintiffs’ words, “the [braking] systems
are defective.” R.306 at 7. “[D]efective[ness]” is a term of art that, in this case at least, nobody
has rigorously applied to the various state law claims. See, e.g., Plas-Tex, Inc. v. U.S. Steel
Corp., 772 S.W.2d 442, 444 (Tex. 1989). In some States, including one of the States at issue
(Texas), a “defect in a strict products liability case” differs from a “defect in an implied
warranty” case. Id. In holding that the plaintiffs’ claims all “center around proof of a defect in
the specific sensor,” R.306 at 7, the district court did not explain how that term matches with, or
does not match with, each state law claim.
The concrete illustrates the abstract. Here are a few representative examples of the state-
law claims filed in this class action and the kinds of questions the parties and district court must
ask and answer on remand as to whether those questions are “common” or “individualized” ones.
An implied-warranty claim under Pennsylvania law, for example, comprises four
elements: (1) an implied warranty of merchantability, (2) breach, (3) causation, and
(4) damages. In re Gen. Motors LLC Ignition Switch Litig., 257 F. Supp. 3d 372, 439 (S.D.N.Y.
2017). A common yes-or-no answer might resolve the first element: Is a vehicle merchantable
if it might unexpectedly brake based on imperfections in a warning device? But that will turn on
Pennsylvania law and the idiosyncrasies of its law with respect to the implied warranty of
merchantability. What of causation or damages? These elements require inquiries into whether
the defect manifested, and the amount of damages (economic or otherwise) each individual
plaintiff suffered. Id. Pennsylvania measures the harm caused by the merchant by looking to “a
manifestation of the breaching defect.” Zwiercan v. Gen. Motors Corp., 2002 WL 1472335, at
*3 (Pa. Com. Pl. May 22, 2002). Because any sudden braking likely manifested only for some
Pennsylvania drivers—those who did not disengage the feature and who live near low-hanging
overpasses or use elevated parking garages—the district court will have to determine whether
these elements are amenable to a common answer.

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A breach of express warranty claim under California law, for example, requires proof
(1) that the plaintiff received a written warranty from the defendant, (2) for which the product
did not perform as promised, (3) that the plaintiff gave reasonable notice to the defendant,
(4) that the defendant failed to repair the product or provide another remedy per the warranty,
and (5) that the plaintiff was harmed. Cal. Com. Code § 2313; Deitsch Plastics Co. v. Gredale
LLC, 602 F. Supp. 3d 1331, 1336 (C.D. Cal. 2022). The first and second elements could lend
themselves to common proof. Because Nissan warranted to “repair or replace defective” brake
components—presumably through the same written warranty—the plaintiffs may be able to
determine the warranty’s scope in one stroke. R.148 at 59. And the class might be able to speak
with one voice as to whether the braking system and software version in each Nissan vehicle are
defective within the meaning of this contract language. Because the breach-of-warranty claims
allege that Nissan failed to repair defective parts, a common answer as to defect could implicate
the second element.
But the last three elements may present more individualized questions. Consider
reasonable notice. Whether a plaintiff gave reasonable notice rests on whether he brought his
Nissan in for repairs. This answer likely differs across the class members, potentially spoiling
commonality. Consider harm. Some class members (perhaps many class members) never
experienced sudden braking. This element, too, may require an individualized inquiry.
Now consider the inquiry over the defendant’s repairs. Nissan offered repairs to class
members who requested them. But given that many members never sought repairs, it likely
follows that Nissan did not offer repairs to some class members, potentially dashing
commonality for this element. A customer, it is true, need not seek a repair if it wouldn’t solve
the problem. See Benkle v. Ford Motor Co., No. SA CV 16-1569-DOC, 2017 WL 9486154, at
*11–12 (C.D. Cal. Dec. 22, 2017). This reality may implicate a common question over the
fourth element: whether the class vehicles’ braking systems contained irreparable defects. But
the district court must analyze this possibility carefully, which includes considering the
possibility that updates to the radar and control unit software materially improved the product
and made any remaining problems fixable.

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Under Illinois law, for example, the Consumer Fraud Act requires a plaintiff to show
(1) a defendant’s deceptive act or practice in commerce, (2) an intent that the plaintiff rely on it,
(3) actual damages, and (4) proximate cause. De Bouse v. Bayer, 922 N.E.2d 309, 313 (Ill.
2009). Common answers might resolve the questions presented by the first element. The
plaintiffs contend that Nissan sold vehicles with faulty braking systems to Illinois residents
without disclosing their limitations. That may implicate a common question about the
deceptiveness of a uniform statement to customers purchasing (or leasing) Nissan vehicles about
whether the automated brakes worked, assuming each vehicle contains the same one. And that
argument for like reasons may involve a common answer to the question whether it occurred in
trade or commerce.
But individualized questions may affect the other elements. Reliance tends to turn on
individual circumstances. To establish proximate causation, the plaintiff must “actually be
deceived by a statement or omission.” Id. at 316. If a consumer “has neither seen nor heard” the
statement or ignored it, it may be difficult to show they have been harmed by it (or for that
matter relied on it). See id. Even if each consumer experiences the same deceptive statement,
they may experience it differently in making individual purchasing decisions. Skeptical
purchasers who do “not rely” on a promotional statement have no claim. See id. That demands
individual determinations because—unlike securities fraud—Illinois lacks a “market theory of
causation” for these claims. Id.
An unjust enrichment claim under New York law, for example, requires proof that (1) the
defendant was enriched, (2) at the plaintiff’s expense, and (3) “it is against equity and good
conscience” for the defendant “to retain what is sought to be recovered.” Mandarin Trading Ltd.
v Wildenstein, 944 N.E.2d 1104, 1110 (N.Y. 2011) (quotation omitted). All three elements
examine the details of the transaction between the parties, the purchaser’s expectations, reliance
on the seller’s statements, and other individualized details. Id. at 1110–11. That reflects the
nature of equitable actions, which draw on “broad considerations of equity and justice” that
frequently change in context. Paramount Film Distrib. Corp. v. State, 285 N.E.2d 695, 698
(N.Y. 1972). Common details about the braking system would seem to do little to resolve the
first two elements. The same likely goes for the third element. Perhaps one could ask whether

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selling any system that unexpectedly brakes is necessarily against good conscience. Even so,
this would not resolve the third element, which examines a plaintiff’s individual damages.
A fraudulent concealment claim under Illinois law, for example, requires (1) a “false
statement” or omission “of material fact,” (2) a defendant’s knowledge of its falsity, (3) a
defendant’s intent to induce the plaintiff to act, (4) the plaintiff’s reliance, and (5) some damages
resulting from that reliance. Connick v. Suzuki Motor Co., 675 N.E.2d 584, 591–93 (Ill. 1996).
Reliance looms large in fraud claims. In this instance, it’s hard to see how the class could
assert with one voice that they had all relied on Nissan’s statements or suffered the same
damages because of that reliance. Illinois law asks “which, if any, of the plaintiffs heard these
representations and relied on them.” Id. at 591. A similar problem haunts the damages inquiry,
which turns on the extent to which each plaintiff relied on each representation. All of this
explains why the Supreme Court characterizes reliance as often “an insuperable barrier to class
certification.” Dukes, 564 U.S. at 351 n.6. The district court will need to examine these
elements closely—as well as consider the possibility that a common question exists over whether
Nissan knew that the class vehicles had faulty braking systems but said nothing.
We provide these examples to show the nature of the “commonality” question and the
need for the question to resolve something that matters to the plaintiffs’ claims. But our analysis
should not be taken too far. Technically, the plaintiffs need only identify one common question
to satisfy Rule 23(a)(2)’s commonality element. See id. at 359. If other questions raise
individual issues, the court’s decision to certify a class must then depend on Rule 23(b)(3)’s
predominance element. See id. Here, however, the district court’s analysis and the plaintiffs’
briefing failed to identify a single legally significant common question because they did not
attempt to match any common question to any element of any of the plaintiffs’ claims.
The plaintiffs resist these conclusions for several reasons. They argue that another case
involving Ford, Daffin v. Ford Motor Co., 458 F.3d 549 (6th Cir. 2009), supports the class-
certification order. But Daffin hurts more than helps them. There, a class of Mercury Villager
buyers sued Ford on the ground that a defective throttle caused the accelerator to stick. Id. at
550. We approved and certified the class because a single product—an identical throttle body in

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each car—presented a common question of defect amenable to classwide resolution. Id. at 552.
Here, in marked contrast, Nissan has provided evidence that software upgrades to the radar and
brake unit stopped the defect for some claimants. That reality shows that each buyer does not
face a common defect.
The plaintiffs insist that Nissan admitted that the radars in each vehicle had a common
defect. But such an admission does not come to grips with Nissan’s efforts to remedy it. The
company presented evidence that it had updated the radar, the control units, and the relevant
software. At issue by the terms of the plaintiffs’ complaint, moreover, is whether a common
question exists over the defectiveness of the braking “systems” and their associated updates, not
just whether the radars are defective. R.241 at 18. A court cannot assess the commonality of
those alleged defective systems without investigating how their components changed.
The plaintiffs claim that the software updates imposed negligible performance
improvements. But Nissan produced evidence that the S1 and S2 software updates, which
improved the radar’s detection function, mitigated the problems experienced by vehicles with the
S0 software. As proof, Nissan identified a decrease in warranty claims for vehicles with the
updated software. The district court must closely examine the effect of these changes on
remand. If a reasonable jury could answer “yes” to the defect question for those members of the
class who did not receive updates and “no” for those who did, the question does not represent a
“common” one within the meaning of Rule 23. See Doster, 54 F.4th at 430–31.
The plaintiffs contend that the details of the various versions of the radar system—and
whether they were defective—amount to a forbidden merits inquiry at the class-certification
stage. Not so. The court must consider the merits to the extent “relevant to determining whether
the Rule 23 prerequisites” are met. Amgen Inc. v. Conn. Ret. Plans & Tr. Funds, 568 U.S. 455,
466 (2013). That analysis often “will entail some overlap with the merits” and in situations like
this one “cannot be helped.” Dukes, 564 U.S. at 351. Analyzing the various manifestations of
the alleged defect is necessary to assess whether common evidence could vindicate the plaintiffs
or Nissan on a classwide basis.

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Plaintiffs’ arguments about a common defect exhausted, they turn to Nissan’s knowledge
of the defect. They claim that common evidence can establish that knowledge even if the radar
system changed over time. But Ford forecloses that line of reasoning. 86 F.4th at 728. As in
that case, Nissan’s understanding of the defect changed with each update. Nissan could
reasonably believe that each software update fixed, or at least ameliorated, any defect for some
plaintiffs. And later claimants, who purchased cars with S2 brake systems, may not have faced
any defect at all.
The plaintiffs offer other reasons why common knowledge might exist. They contend
that Nissan’s knowledge didn’t change over time because it continued to disclose the risk of false
activations in its manuals and before the district court. And they argue that Nissan’s witnesses
and expert testimony fail to establish that the upgrades prevented phantom breaking. But none of
this addresses the question left unanswered below: Does awareness of a general risk of product
limitations—true for any automatic braking system, as no perfect one yet exists—establish
knowledge of a common defect? And none of this, most critically, comes to grips with the
requirements of looking at these issues through the specific lens of each cause of action and each
of its elements. See Doster, 54 F.4th at 430–31; Dukes, 564 U.S. at 350–52.
B. Predominance
Commonality issues taint the predominance inquiry from the get-go. For classes certified
under Civil Rule 23(b)(3), as this one was, common questions of law or fact must “predominate
over any questions affecting only individual members.” The rule requires a court to put the
common issues on one side, the individual issues on the other, then “qualitatively evaluate which
side ‘predominates.’” Fox v. Saginaw County, 67 F.4th 284, 300 (6th Cir. 2023). This balancing
works only if the district court properly identified at least one common (non-individualized)
issue. Having determined that the district court failed to do so, especially in light of Ford and
Doster, it follows that the predominance inquiry requires a second look.
In taking that second look, the district court must consider, and account for, some of the
“individualized determinations” that might be “ill-equipped for classwide proof.” Tarrify Props.,
LLC v. Cuyahoga County, 37 F.4th 1101, 1106 (6th Cir. 2022). Accounting for these

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individualized determinations in connection with any truly common questions of law and fact is
indispensable to the analysis demanded.
C. Expert Witnesses Under Daubert
The Supreme Court requires parties to “satisfy through evidentiary proof” that they “in
fact” meet the elements in Civil Rule 23. Behrend, 569 U.S. at 33. Which prompts this
question: When challenged expert testimony is relevant to class certification, must a district
court perform a Daubert analysis of the evidence? The Third, Fifth, Seventh, and Eleventh
Circuits say yes. See, e.g., In re Blood Reagents Antitrust Litig., 783 F.3d 183, 187 (3d Cir.
2015); Prantil v. Arkema Inc., 986 F.3d 570, 574–76 (5th Cir. 2021); Am. Honda Motor Co. v.
Allen, 600 F.3d 813, 815 (7th Cir. 2010); Loc. 703, I.B. of T. Grocery & Food Emps. Welfare
Fund v. Regions Fin. Corp., 762 F.3d 1248, 1258 n.7 (11th Cir. 2014). The Eighth and Ninth
Circuits perform a more limited Daubert analysis. See, e.g., In re Zurn Pex Plumbing Prods.
Liab. Litig., 644 F.3d 604, 614–15 (8th Cir. 2011) (assessing a subset of the factors under
Daubert); Sali v. Corona Reg’l Med. Ctr., 909 F.3d 996, 1003–06 (9th Cir. 2018) (using Daubert
to assess the weight of evidence, rather than to exclude evidence).
We agree with the majority view. If challenged expert testimony is material to a class
certification motion, the district court must demonstrate the expert’s credibility under Daubert.
Class certification requires the plaintiffs to provide “evidentiary proof” that they meet the
elements of Rule 23. Behrend, 569 U.S. at 33. Careful qualification of experts ensures that
expert evidence “both rests on a reliable foundation and is relevant to the task at hand.” Daubert
v. Merrell Dow Pharms., Inc., 509 U.S. 579, 597 (1993). If expert testimony is insufficiently
reliable to satisfy Daubert, it “cannot ‘prove’ that the Rule 23(a) prerequisites have been met ‘in
fact’” through acceptable evidentiary proof. Blood Reagents, 783 F.3d at 187 (quotation
omitted). It’s no surprise that the Supreme Court and most of our sister circuits that have spoken
suggest that Daubert—interpreting Evidence Rule 702—applies to expert testimony at the class-
certification stage. Dukes, 564 U.S. at 354; see Am. Honda, 600 F.3d at 816; Blood Reagents,
783 F.3d at 187; Prantil, 986 F.3d at 576.

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The challenged expert report is a critical piece of the plaintiffs’ effort to answer this
commonality inquiry: Does each class vehicle contain the same allegedly deficient braking
system, or do different cars have materially different automated brakes? Steve Loudon, an
automotive control systems expert hired by the plaintiffs, says yes: The “primary defect . . . is
the ARS410 radar’s inability to properly discriminate between” real and fake obstacles. R.245-5
at 32. In support, he reviewed documents obtained in discovery and drove some of the Class
Vehicles under bridges and over railroad crossings. If reliable, Loudon’s testing helps to identify
a common deficiency. Given these stakes, the district court must assess if his testimony reliably
reflects the “knowledge and experience of his discipline.” Kumho Tire Co. v. Carmichael, 526
U.S. 137, 148 (1999) (quotation omitted).
Even if reliable, it deserves note, Loudon’s proffered evidence does not suffice by itself
to show a flaw in all of the cars. He did not test vehicles with the S2 software update. And his
paper review of the software updates asserts without any evidentiary support that each version
shares “substantially similar software” and “basic system architecture.” R.245-5 at 20–21. That
bald statement alone does not inform whether the S2 upgrade created materially different braking
systems, let alone whether a common defect infiltrates each Class Vehicle. In the end, the
plaintiffs face at least two hurdles, not one, on this score. They need to establish that their expert
satisfies Daubert, and their expert needs to offer an evidence-backed opinion on each material
aspect of the commonality inquiry.
The plaintiffs respond that we should not decide the Daubert question because the district
court found that the parties’ experts were “not ‘critical’ to resolving the class certification
motion.” Appellee’s Br. 42. But the court found only that the plaintiffs’ damages experts are
not critical. The other experts provide a key insight on whether purported flaws differed among
models. That explains why Nissan challenged Loudon’s expert report on Daubert grounds
below and on appeal.
The plaintiffs argue that Lyngaas v. Curaden Ag forecloses this approach. 992 F.3d 412
(6th Cir. 2021). It does not. In Lyngaas, we held that the evidence rules governing
authentication do not necessarily apply at the class-certification stage. Id. at 428–29. But we
addressed “nonexpert evidence” in making the point. Id. Unlike the rules of authentication,

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Daubert “make[s] certain that an expert . . . employs in the courtroom the same level of
intellectual rigor that characterizes the practice of an expert in the relevant field.” Kumho Tire,
526 U.S. at 152.
The plaintiffs point out that Daubert exists to “protect juries from being swayed by
dubious scientific testimony” and argue that this consideration has no purchase here because the
judge alone decides class certification. See In re Zurn, 644 F.3d at 613. Even so, the text and
principles of Daubert still apply to this fact-based inquiry. Evidence Rule 702 does not
distinguish between jury and bench trials. And Daubert “ensure[s] the reliability and relevancy
of expert testimony,” a touchstone of a careful analysis of evidentiary proof. Kumho Tire, 526
U.S. at 152.
Last and least, the claimants argue that this approach prematurely decides the merits.
That objection misapprehends Rule 23. The Daubert inquiry does not resolve who wins. It
resolves whether “a decisionmaker can answer the Plaintiffs’ questions all at once through
evidence common to the class” and, if need be, through evidence provided by a qualified expert.
Doster, 54 F.4th at 435 (quotation omitted). When a court does consider a merits question, it is
only “to the extent” that it is “relevant to determining whether the Rule 23 prerequisites” are met.
Amgen, 568 U.S. at 466.
We vacate and remand for further proceedings consistent with this opinion.

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