Thor Zurbriggen v. Twin Hill Acquisition, Inc.

In the
United States Court of Appeals
For the Seventh Circuit
____________________
No. 25-1963
T HOR ZURBRIGGEN, et al.,
Plaintiffs-Appellants,
v.
T WIN HILL A CQUISITION, INC., et al.,
Defendants-Appellees.
____________________
Appeal from the United States District Court for the
Northern District of Illinois, Eastern Division.
No. 1:17-cv-05648 — John J. Tharp, Jr., Judge.
____________________
A RGUED FEBRUARY 13, 2026 — D ECIDED J UNE 16, 2026
____________________
Before BRENNAN, Chief Judge, and HAMILTON and
SCUDDER , Circuit Judges.
BRENNAN, Chief Judge. In 2015, American Airlines con-
tracted with Twin Hill Acquisition, Inc., to manufacture new
uniforms for its employees. After American released the new
apparel, hundreds of employees complained of health prob-
lems ranging from itchy eyes to severe allergic reactions.
Some claimed they suffered reactions just from being near the
Twin Hill uniforms.

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2 No. 25-1963
Many employees sued the airline and the manufacturer
under the Class Action Fairness Act, 28 U.S.C. § 1332(d)(2),
bringing claims under both products liability and intentional
tort theories of liability. After resolving a jurisdictional issue,
the district court excluded the plaintiffs’ expert witnesses and
granted summary judgment for the defendants. The plaintiffs
appeal. We adopt the district court’s first-rate opinion, limit-
ing our discussion to the jurisdictional question and plaintiffs’
invocation of res ipsa loquitur in support of its products lia-
bility theories.
I. Background
A. Factual
American Airlines rolled out a new line of uniforms for
flight attendants, pilots, and other “above the wing” employ-
ees throughout 2016. But the uniforms, manufactured by
Twin Hill, quickly prompted backlash. After the flight attend-
ants’ union encouraged employees to report their concerns,
American received hundreds of complaints. Some claimed
problems with sizing, while many others complained the uni-
forms were making them “itchy” or giving them “scratchy”
eyes and throats. Still others reported different health-related
complaints, like allergic reactions, rashes, hives, dermatitis,
throat swelling, and respiratory symptoms.
One month later, American reversed its rollout of the Twin
Hill uniforms. Employees were allowed to wear their old uni-
forms or to purchase off-the-rack substitutes. By March 2017,
American offered another uniform option produced by a dif-
ferent company. Yet, some employees still claimed they were
experiencing “proximity reactions” to the Twin Hill uni-
forms—that is, they had severe allergic reactions simply from

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No. 25-1963 3
being near people wearing them. By 2020, American had fully
replaced the Twin Hill uniforms with alternatives from
Lands’ End.
Before and after rolling out the Twin Hill uniforms, Amer-
ican conducted wear tests and chemical analysis to ensure the
uniforms were safe. One pre-release test led to complaints of
irritation, so American retained Intertek for expert lab evalu-
ation. Intertek performed a test and found chemicals that the-
oretically could trigger allergic reactions or rashes, but it
opined the doses discovered were too low to produce those
results. It also noted that some of the chemicals were common
in perfumes, so they could have been transferred onto the gar-
ments during the wear test. Later, Intertek performed a sec-
ond test of unworn garments, which produced similar results.
In addition to Intertek, the National Institute for Occupa-
tional Safety and Health (NIOSH) tested the uniforms. Inter-
tek had concluded it was “possible, but unlikely” that some
of the chemicals in the uniforms could cause a rash if people
were already allergic to these chemicals, given the low quan-
tities. NIOSH concurred, concluding that the “results of the
uniform samples testing did not reveal a pattern of chemical
or metal contamination that would indicate a cause for the
widespread reported symptoms.” NIOSH also found it highly
unlikely that the uniforms could cause proximity reactions.
Other independent testing reached the same conclusion.
B. Procedural
A group of 74 named plaintiffs sued Twin Hill, American
Airlines, and several other defendants in August 2017. Invok-
ing federal jurisdiction under the Class Action Fairness Act of
2005 (CAFA), see 28 U.S.C. § 1332(d)(2), the plaintiffs raised

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4 No. 25-1963
several pure questions of state tort law and sought to certify
two different classes of injured employees.1
After several motions to dismiss and discovery battles, the
plaintiffs filed their third amended complaint. This pleading
distilled their grievances down to four. Against Twin Hill,
they asserted strict and negligent products liability theories,
arguing that the uniforms were defective and caused plain-
tiffs’ injuries. And against both Twin Hill and American, they
brought battery and intentional infliction of emotional dis-
tress claims, alleging the companies forced employees to wear
defective and harmful uniforms.
Notably, this third amended complaint also announced
that the plaintiffs had “elected to drop their class claims in
order to proceed to bellwether trials.” Elsewhere in that com-
plaint, plaintiffs stated “they will not be seeking class certifi-
cation for the proposed classes due to, among other things,
passage of time.” Discovery continued under this version of
the complaint.
In September 2024, Twin Hill and American moved for
summary judgment as to the first flight of bellwether plain-
tiffs. These defendants also moved to exclude the testimony
of two expert witnesses offered by the plaintiffs: Dr. Arch Car-
son and Dr. Peter Hauser. The defendants’ summary judg-
ment motions hinged on the exclusion of these experts. No
professional testing had revealed chemicals in the uniforms
1 As the district court noted, the plaintiffs hail from many states, com-
plicating the choice of law inquiry. Yet the court explained how all possi-
ble jurisdictions required the same threshold questions to be satisfied for
the plaintiffs to proceed. We agree that the choice of law issue is not dis-
positive.

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No. 25-1963 5
capable of causing the range of harmful reactions plaintiffs al-
leged. So, these two experts supplied the sole evidence of
harm, defects, and causation of the plaintiffs’ injuries.
In response, the plaintiffs invoked the tort doctrine of res
ipsa loquitur. Though plaintiffs had not referenced this prin-
ciple in their amended complaint, they did so in response to
Twin Hill’s motion for summary judgment. To plaintiffs, their
two experts did not need to provide a specific theory of defect
or causation. Instead, circumstantial evidence supported their
experts’ opinions on the likelihood of these injuries occurring
in the absence of a defect. Accordingly, plaintiffs sought to
shift the burden of proof onto the defendants.
The district court granted the defendants’ motions for
summary judgment. In a thorough opinion, the court identi-
fied a weakness in the plaintiffs’ case. Under each of plaintiffs’
four liability theories, they needed to show the uniforms were
actually defective and caused their injuries. To make that
showing, plaintiffs required expert testimony. The district
court concluded that Dr. Carson and Dr. Hauser each had em-
ployed an unreliable methodology, so their reports were ex-
cluded from the summary judgment record. That meant the
plaintiffs’ liability theories faltered because they could not
connect the alleged harms to the condition of the uniforms.
The plaintiffs appeal.
II. Subject Matter Jurisdiction
Before turning to the merits, we must address jurisdiction.
Chi. Tchrs. Union, Loc. 1 v. Educators for Excellence, Inc., 159
F.4th 524, 528 (7th Cir. 2025). Whether the parties brief this
issue or not, appellate courts have an independent obligation

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6 No. 25-1963
to ensure that jurisdiction is proper. Knopick v. Jayco, Inc., 895
F.3d 525, 528 (7th Cir. 2018).
A. Royal Canin and CAFA
A district court has original jurisdiction under CAFA if a
plaintiff can satisfy three prerequisites. First, the amount in
controversy must exceed $5,000,000. 28 U.S.C. § 1332(d)(2).
Second, certain minimal diversity requirements must be met.
Id. at (d)(2)(A)–(C). Third, the action must be “a class action.”
Id. at (d)(2).2 The first two are not at issue here, but the third
raises some uncertainty.
CAFA defines a “class action” as “any civil action filed un-
der rule 23 of the Federal Rules of Civil Procedure or similar
State statute.” 28 U.S.C. § 1332(d)(1)(B). This court was the
first to hold that subsequent developments in a case, such as
failing to achieve or pursue class certification, do not destroy
CAFA jurisdiction. Cunningham Charter Corp. v. Learjet, Inc.,
592 F.3d 805, 806–07 (7th Cir. 2010). The logic behind this rule
is that the statute only requires the action to be “filed under
Rule 23.” Id. at 806 (emphasis added). Like the “time-of-filing”
rules that apply to amount in controversy and party citizen-
ship in ordinary diversity cases, this rule fixes jurisdiction
based on the terms of the complaint. Sykes v. Cook Inc., 72 F.4th
195, 205 (7th Cir. 2023) (amount in controversy); Winforge, Inc.
v. Coachmen Indus., Inc., 691 F.3d 856, 867 (7th Cir. 2012) (party
citizenship).
While this case was pending in the district court, the Su-
preme Court decided Royal Canin U.S.A., Inc. v. Wullschleger,
2 The district court should also decline to exercise jurisdiction in some
kinds of cases, 28 U.S.C. § 1332(d)(4), but this issue is not disputed here.
Morrison v. YTB Int’l, Inc., 649 F.3d 533, 535–36 (7th Cir. 2011).

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No. 25-1963 7
604 U.S. 22 (2025). That case reminds courts that the “plaintiff
is ‘the master of the complaint,’ and therefore controls much
about her suit.” Id. at 35. This control “extends beyond the
time her first complaint is filed,” allowing a plaintiff to amend
away all prior grounds for the court’s jurisdiction. Id. An
amendment “effectively remake[s] the suit,” including “its ju-
risdictional basis: The reconfiguration accomplished by an
amendment may bring the suit either newly within or newly
outside a federal court’s jurisdiction.” Id. at 35–36.
Though Royal Canin is a case about removal jurisdiction, it
reaffirmed the point that jurisdiction in “original federal
cases” must be strictly tied to “an amended pleading.” Id. at
36 (citing Rockwell v. Int’l Corp. v. United States, 549 U.S. 457
(2007)). And it noted that plaintiffs can “destroy[] diversity
jurisdiction” in an original action by changing the parties to
the case. Id. at 37. “In short, the rule in original cases,” which
says “that jurisdiction follows the amended … pleading,” ap-
plies “across the board.” Id.
Royal Canin does not discuss CAFA jurisdiction, but its
reasoning is still relevant. A plaintiff who amends his
complaint to remove parties needed for minimal diversity, for
example, would unquestionably change the basis for jurisdic-
tion under CAFA. Id. It follows that an amendment removing
class allegations would accomplish the same effect, as the case
would no longer be “filed under Rule 23.” 28 U.S.C.
§ 1332(d)(1)(B).
In the third amended complaint, plaintiffs did exactly that.
They stated they “have elected to drop their class claims in
order to proceed to bellwether trials.” And though their com-
plaint still included a section entitled “Class Action Allega-
tions,” the plaintiffs added a footnote saying, “As Plaintiffs

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8 No. 25-1963
have informed … the Court, they will not be seeking class cer-
tification for the proposed classes due to, among other things,
passage of time.” They believed jurisdiction still existed “be-
cause jurisdiction was proper at the time of filing.” But this
contradicts the rule in Royal Canin that an amended complaint
“effectively remake[s] the suit.” 604 U.S. at 35. So, plaintiffs’
pleading of the third amended complaint may have resulted
in the district court losing CAFA jurisdiction for some time.
B. Fourth Amended Complaint
After the Supreme Court issued Royal Canin, the district
court perceptively noticed this potential problem. So, it or-
dered supplemental briefing on “the effect of the plaintiffs’
decision to drop their class allegations … on this Court’s sub-
ject-matter jurisdiction.” Both sides responded that the court
still had jurisdiction. They noted that Royal Canin considered
a different statute (28 U.S.C. § 1367) in a different context (re-
moval jurisdiction) and that the Supreme Court decision did
not discuss CAFA. And the parties pointed to this court’s de-
cision in In re Burlington Santa Fe Railway, 606 F.3d 379 (7th
Cir. 2010), which ruled that jurisdiction is secure “even
though, after removal, the plaintiffs amended their complaint
to eliminate the class allegations.” Id. at 380.
In tandem with their response, the plaintiffs filed a fourth
amended complaint. That document deletes the language
from the third amended complaint about not seeking class
certification, pleading all CAFA’s jurisdictional prerequisites
with more specificity.
The district court “conclude[d] that it possesses subject-
matter jurisdiction over this action under the Class Action
Fairness Act notwithstanding the lack of a certified class” in a

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No. 25-1963 9
footnote to its summary judgment opinion. Though the court
noted that In re Burlington likely stood on thin ice after Royal
Canin, it declined to deviate from Seventh Circuit precedent
without clearer guidance.3 In sum, the court reasoned that the
“operative fourth amended complaint unambiguously in-
vokes CAFA and pleads its jurisdictional prerequisites.”
The district court reached the correct conclusion. What
matters under CAFA is whether the action was “filed under
rule 23.” 28 U.S.C. § 1332(d)(1)(B). As Royal Canin teaches,
every amended complaint effectively remakes the suit, in-
cluding “its jurisdictional basis.” 604 U.S. at 35. Even if the
third amended complaint undercut subject matter jurisdic-
tion, the fourth amended complaint effectively re-filed the
case as a “class action,” securing jurisdiction under CAFA.
The plaintiffs revised their complaint once to destroy jurisdic-
tion, and then they did so again to save it.
Under this reasoning, the district court had subject matter
jurisdiction over this case when it granted the defendants
summary judgment. We move next to the merits.
III. Expert Witness Exclusions and Intentional Torts
The district court resolved this case for the defendants on
summary judgment. Rather than repeat that court’s analysis
on the exclusion of plaintiffs’ expert witnesses and plaintiffs’
intentional tort liability theories, on those topics we incorpo-
rate its rulings by reference. See generally Zurbriggen v. Twin
3 Because this issue is not squarely presented, we need not decide
whether In re Burlington has been directly overruled by Royal Canin. Any
future consideration of removal jurisdiction under CAFA, though, must
consider the tension between these cases.

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10 No. 25-1963
Hill Acquisition Co., Inc., No. 1:17-cv-5648, 2025 WL 1092973
(N.D. Ill. Apr. 11, 2025).4
As the district court recognized, the plaintiffs failed to
identify any specific defect with the Twin Hill uniforms. And
the district court properly excluded the expert testimony of
Dr. Carson and Dr. Hauer because of their unreliable meth-
ods. Even these experts, moreover, concede that there was no
identifiable chemical or group of chemicals in the uniforms
capable of triggering the range of reactions the plaintiffs al-
lege. Without this expert testimony, there is no evidence from
which a reasonable jury could conclude that the defendants
caused plaintiffs harm—especially not that the uniforms
caused proximity reactions harming plaintiffs from afar.
IV. Res Ipsa Loquitur
In an effort to overcome the lack of direct evidence of any
defect, the plaintiffs raise the doctrine of res ipsa loquitur.
They submit that circumstantial evidence in the record sup-
ports an inference under this doctrine that Twin Hill is liable
for their injuries on their products liability theories.
On appeal, plaintiffs offer two types of res ipsa arguments.
First, they ask us to apply the Illinois law doctrine developed
in Tweedy v. Wright Ford Sales, Inc., 357 N.E.2d 449 (Ill. 1976),
which applies only to strict liability theories. Second, they cite
the traditional variant of res ipsa loquitur to prove their neg-
ligent manufacturing arguments against Twin Hill.
4 We thank the Lawyers for Civil Justice for its helpful amicus curiae
brief in this case discussing the 2023 amendments to Federal Rule of Evi-
dence 702 on expert witnesses.

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No. 25-1963 11
The district court limited its discussion of res ipsa loquitur
to a footnote, finding that “[t]he record decidedly forecloses
any … notion” that the doctrine applies to this case.5 Because
the plaintiffs make this issue a core component of this appeal,
however, their reliance on these related doctrines warrants a
deeper discussion.
A. Strict Liability: Tweedy Doctrine
Under Illinois law,6 “[a]n injured plaintiff may allege one
of two types of products liability claims: a strict liability claim
or a negligence claim.” Salerno v. Innovative Surveillance Tech.,
Inc., 932 N.E.2d 101, 108 (Ill. App. Ct. 2010) (citing Blue v. Env’t
Eng’g, Inc., 828 N.E.2d 1128, 1137 (Ill. 2005)). In a strict liability
5 District Court D.E. 701 at 41 n.19. The court listed the following evi-
dence in support of its conclusion that negligence through res ipsa loqui-
tur could not be inferred:
 plaintiffs’ symptoms were not unique to exposure to a toxic sub-
stance;
 the Intertek results do not indicate that any detected substance
could trigger the plaintiffs’ symptoms at low concentrations;
 several alternative explanations for plaintiffs’ symptoms were not
only plausible but endorsed by plaintiffs’ own treating physi-
cians;
 the actual rate of symptomology among exposed employees is un-
known; and, in any case,
 a toxic chemical on the Twin Hill uniforms would not necessarily
reflect that the manufacturer was negligent, as opposed to post-
production corruption.
6 We recognize that the parties disputed the choice of law before the
district court. See supra note 1. The plaintiffs have proceeded on appeal as
if the Tweedy doctrine governs this case, though they have not cited to
states other than Illinois recognizing this rule. We proceed as if Illinois law
applies on this theory because the choice of law does not change the out-
come.

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12 No. 25-1963
claim, “the focus of the inquiry is on the condition of the prod-
uct itself.” Id. As we have explained, “A strict liability claim is
premised on a defect that renders a product dangerous be-
cause the product fails to perform in the manner one reason-
ably expects it to in light of its nature and intended function.”
Bensenberg v. FCA US LLC, 31 F.4th 529, 535 (7th Cir. 2022).
Ordinarily, plaintiffs need to prove three elements to
make a prima facie showing of strict products liability. They
must show “the injury resulted from a condition of the prod-
uct,” “the condition was an unreasonably dangerous one,”
and “the condition existed at the time it left the defendant’s
control.” DiCosolo v. Janssen Pharms., Inc., 951 N.E.2d 1238,
1243 (Ill. App. Ct. 2011). This burden would typically be sat-
isfied by proffering expert testimony identifying a dangerous
defect in the product. Kirk v. Clark Equip. Co., 991 F.3d 865, 878
(7th Cir. 2021) (quoting Mikolajczyk v. Ford Motor Co., 901
N.E.2d 329, 345 (Ill. 2008)).
But in Tweedy, the Supreme Court of Illinois articulated an
alternative pathway to make this prima facie showing. There,
the brakes on a car failed without explanation, and the driver
was injured in the subsequent crash. 357 N.E.2d at 450–51.
The plaintiff offered no expert testimony supporting a finding
that the brakes were defective at the time they left the manu-
facturer’s control. Id. at 451. But how else could the accident
have occurred? Sure, “[e]lves may have played ninepins”
with the product, but absent such absurd possibilities, “an ac-
cident can itself be evidence of liability.” Welge v. Planters Life-
savers Co., 17 F.3d 209, 211 (7th Cir. 1994). So, the court al-
lowed the strict liability claim to proceed.
As long as plaintiffs can show that “the product failed to
perform in the manner reasonably to be expected in light of

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No. 25-1963 13
[its] nature and intended function,” and there is no evidence
of “abnormal use or reasonable secondary causes,” they can
make out a “prima facie case that a product was defective.”
Tweedy, 357 N.E.2d at 452 (citation modified). In other words,
the plaintiff can bypass proof of a specific dangerous defect
so long as “the product failed to perform as expected,” and
there are no better explanations for its failure. Bensenberg, 31
F.4th at 536.
Simply put, the Tweedy doctrine does not apply here. In
car crash cases, like Tweedy or Bensenberg, the connection be-
tween the alleged defect and the injury is usually obvious.
Brakes do not normally fail absent a defect, and it is not hard
to see how the presumed brake failure caused the injuries.
That makes the Tweedy doctrine a poor fit for this case. Un-
like brake failures, it does not follow that the uniforms could
cause the wide range of symptoms reported by American’s
employees. The Tweedy doctrine does not satisfy plaintiffs’
burden to show that a defect caused their injuries—it goes to
“the condition of the product” when it left the “manufac-
turer’s control,” not whether the injury is “the result of the
condition of the product.” Parker v. Freightliner Corp., 940 F.2d
1019, 1026 (7th Cir. 1991). But after the district court excluded
their experts, the plaintiffs had no evidence that the injuries
were “the result of the condition of the product.” Id.
Add to this that the Tweedy factors do not match the facts
here. The plaintiffs stretch the doctrine’s logic by saying the
uniforms “failed to perform as expected.” Bensenberg, 31 F.4th
at 536. These uniforms did not “fail” in the way Illinois courts
normally understand the term—they did not break, collapse,
or malfunction. Varady v. Guardian Co., 506 N.E.2d 708, 712 (Ill.
App. Ct. 1987) (crutches collapse); Alvarez v. Am. Isuzu Motors,

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14 No. 25-1963
749 N.E.2d 16, 21–22 (Ill. App. Ct. 2001) (car transmission fail-
ure); Pike v. ABSS Mfg. Co., No. 1-21-0676, 2023 WL 5202396,
at *1 (Ill. App. Ct. Aug. 14, 2023) (ladder collapse); Weedon v.
Pfizer, Inc., 773 N.E.2d 720, 722 (Ill. App. Ct. 2002) (implanted
medical device malfunction); DiCosolo, 951 N.E.2d at 1243
(medicinal fentanyl patch presumed defective when it re-
leased a lethal dose of the drug). And the plaintiffs cannot
successfully exclude “reasonable secondary causes” of fail-
ure. Tweedy, 357 N.E.2d at 452. As the district court observed,
all the bellwether plaintiffs in the case raise different theories
of harm and had different underlying medical conditions.
Even before the experts were excluded, their testimony could
not establish that substances on the uniforms alone accounted
for these harms.
Read together, these two points show why the Tweedy doc-
trine does not apply here. Res ipsa-style theories are appro-
priate when the fact that an injury occurred “speaks for itself.”
Ruark v. Union Pac. R.R., 916 F.3d 619, 623 (7th Cir. 2019). That
the plaintiffs here experienced various reactions simply does
not signal the existence of a defect or an error without more
evidence. Alternative explanations could account for the inju-
ries of these plaintiffs; a defect is not the most obvious answer.
B. Negligence: Res Ipsa Loquitur
The plaintiffs also ask us to apply the traditional variant
of res ipsa loquitur for their negligent manufacturing theory.
This burden is even higher for a negligence claim than for a
strict liability claim. “For res ipsa loquitur to apply, the plaintiff
must plead and prove that he was injured (1) in an occurrence
that ordinarily does not happen in the absence of negligence
(the probability element) (2) by an agency or instrumentality
within the defendant’s exclusive control (the control

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No. 25-1963 15
element).” Johnson v. Armstrong, 211 N.E.3d 355, 367–68 (Ill.
2022). Illinois courts emphasize that “[w]hether res ipsa loqui-
tur applies is a question of law to be decided in the first in-
stance by the trial court.” Id. at 368.
The district court correctly concluded that no evidence in
the record supported the plaintiffs’ arguments on prong one.
See supra note 5. And we also note that the plaintiffs cannot
establish the control prong either. The uniforms here were
manufactured in many different factories and shipped across
the world by multiple intermediaries. So, Twin Hill had long
since relinquished control over them. By the time the uni-
forms were tested, moreover, many had been washed and
worn, eroding Twin Hill’s control even further. No res ipsa
loquitur inference could prove that the plaintiffs were injured
as a result of negligent manufacturing by Twin Hill. That is
presumably why plaintiffs focus their arguments on the
Tweedy doctrine more than traditional res ipsa loquitur.
The district court properly granted summary judgment to
the defendants on both of plaintiffs’ products liability theo-
ries.
V. Conclusion
Seeing no jurisdictional problem, we adopt the district
court’s well-reasoned opinion in full. And for the reasons ex-
plained, neither the Tweedy doctrine nor res ipsa loquitur help
the plaintiffs satisfy their evidentiary burden on their prod-
ucts liability theories.
A FFIRMED

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