In the 

United States Court of Appeals 

For the Seventh Circuit ____________________

No. 14‐2207

KENT HIGGINS, et al.,

Plaintiffs‐Appellants,

v.

KOCH DEVELOPMENT CORPORATION,

Defendant‐Appellee.

____________________

Appeal from the United States District Court for the

Southern District of Indiana, Evansville Division.

No. 3:11‐cv‐81 — Richard L. Young, Chief Judge.

____________________

ARGUED APRIL 9, 2015 — DECIDED JULY 20, 2015

____________________

Before FLAUM, RIPPLE, and WILLIAMS, Circuit Judges.

FLAUM, Circuit Judge. After the district court disquali‐

fied plaintiff Kent Higgins’s causation expert—enlisted to

prove that Higgins developed asthma and reactive air‐

ways dysfunction syndrome as a consequence of inhaling

chlorine gas at an amusement park—he argued that he

did not need an expert to prove negligence at all. Alterna‐

tively, Higgins argued that his treating physician could

serve as such an expert. The district court disagreed, con‐
2 No. 14‐2207

sidering the causation issue too complex for an unassist‐

ed jury, and deeming Higgins’s treating physician’s quali‐

fications and methodology too uncertain to permit her to

opine on such matters. Consequently, the district court

granted summary judgment in favor of the defendant.

We affirm.

I. Background

On June 20, 2009, Kent and Jennifer Higgins, along

with their two children, visited Santa Claus, Indiana’s

Holiday World & Splashin’ Safari amusement park

(“Holiday World,” for ease of reference)—owned and

operated by defendant Koch Development Corporation.

During their stay, the filter pump connected to the park’s

lazy river (dubbed the “Bahari River”) malfunctioned

due to a tripped circuit breaker. As the park’s staff

worked to fix the problem, pool chemicals—bleach and

hydrochloric acid—accumulated in the pump. When the

pump finally restarted, these chemicals discharged into

the water and a cloud of chlorine gas released into the air.  

At that moment, the Higginses were not near the Ba‐

hari River. But their niece apparently was—and soon

thereafter, the Higginses received a cell phone call alert‐

ing them that she was “in trouble,” prompting them to

head in that direction. When they arrived, Kent Higgins

(“Higgins”) inhaled an unspecified amount of chemical

fumes that lingered in the air. Complaining of chest

tightness, burning eyes, shortness of breath, and nausea,

Higgins visited the emergency room later that day, where

he was diagnosed with “mild chemical exposure” and

discharged with instructions to follow up with his prima‐

ry care physician.
No. 14‐2207 3

Higgins saw a pulmonologist later that summer, but

waited more than a year before consulting his primary

care physician, who referred Higgins to a second pul‐

monologist, Dr. Linda Haacke. Dr. Haacke diagnosed

Higgins with reactive airways dysfunction syndrome

(“RADS”) and chronic asthma on August 18, 2010 (more

than fourteen months after the incident at Holiday

World). According to Dr. Haacke, RADS is a syndrome

that results in an acute change in one’s airways functions,

and generally occurs following a single exposure to a

significant amount of irritant. Wheezing, bronchospasm,

and shortness of breath are symptomatic of both RADS

and asthma. Dr. Haacke based her diagnosis on her eval‐

uation of Higgins, coupled with the results of a pulmo‐

nary function study conducted by the pulmonologist that

Higgins had seen a year earlier. Since his initial visit,

Higgins has seen Dr. Haacke about once every six

months, and she continues to prescribe him medication

for his conditions.

In May 2011, Higgins brought this negligence suit

against Koch Development Corporation.1 To prove his

case, Higgins sought to designate Dr. Anthony Margheri‐

ta (who examined Higgins for purposes of this litigation)

as his causation expert. The district court, however,

granted Koch’s motion to disqualify Dr. Margherita for

                                                 

1 In addition to damages for Higgins himself, the complaint sought

medical expenses allegedly incurred by Higgins’s wife, Jennifer;

their two children; and another family, the Taylors (all of whom ap‐

parently also inhaled chemical fumes at Holiday World on June 20,

2009). But those claims were resolved in the district court and are not

relevant to this appeal.  
4 No. 14‐2207

failing to establish a reliable methodology (a ruling that

Higgins does not challenge on appeal). Shortly thereafter,

Koch filed a motion for summary judgment, arguing that

Higgins could not prove that the chemical fumes caused

his injuries.

In opposition, Higgins—now without a causation ex‐

pert—tried to persuade the district court that he did not

need an expert to testify regarding causation in order to

prove his case. Alternatively, he argued that Dr. Haacke

should be permitted to serve as such an expert. The dis‐

trict court disagreed on both accounts, finding an expert

essential to a jury’s understanding of the issues and—on

the record before it—deeming Dr. Haacke unqualified to

opine on chlorine’s effects on the human pulmonary sys‐

tem and her methodology too uncertain to determine its

reliability. Without a proper causation expert, the district

court concluded, Higgins could not prove his negligence

claim, and so the court granted summary judgment in

favor of Koch.  

Higgins appeals.

II. Discussion

We review a district court’s grant of summary judg‐

ment de novo. Fix v. Quantum Indus. Partners LDC, 374

F.3d 549, 552 (7th Cir. 2004). However, our review of the

district court’s decision concerning the admission of ex‐

pert testimony, even in the summary judgment context,

is slightly more nuanced. We review de novo whether

the district court properly followed the framework set

forth in Daubert v. Merrell Dow Pharmaceuticals, Inc., 509

U.S. 579 (1993). United States v. Hall, 165 F.3d 1095, 1101
No. 14‐2207 5

(7th Cir. 1999). If the district court properly applied that

framework (and Higgins concedes that, in evaluating the

sufficiency of Dr. Haacke’s opinion testimony, it did), we

review the court’s decision to exclude expert testimony—

that is, its application of the Daubert framework—for an

abuse of discretion. Gayton v. McCoy, 593 F.3d 610, 616

(7th Cir. 2010).  

In this diversity action, Indiana law governs whether

an expert is needed to prove causation. See Wallace v.

McGlothan, 606 F.3d 410, 419–20 (7th Cir. 2010). Under

Indiana law, proving negligence in a case like this one

requires proof of both general and specific (or individual)

causation. 7‐Eleven, Inc. v. Bowens, 857 N.E.2d 382, 389

(Ind. Ct. App. 2006). The law of the Seventh Circuit

acknowledges this same dichotomy. See Myers v. Ill. Cent.

R.R. Co., 629 F.3d 639, 641–42 (7th Cir. 2010). General

causation refers to “whether the substance at issue had

the capacity to cause the harm alleged, while ‘individual

causation’ refers to whether a particular individual suf‐

fers from a particular ailment as a result of exposure to a

substance.” 7‐Eleven, 857 N.E.2d at 389. The district court

concluded that, without an appropriate expert, Higgins

could not establish specific causation—that is, that the

inhalation of chemical fumes caused his health condi‐

tions. Higgins, however, maintains that he does not need

an expert to establish that the incident at the Bahari River

sparked his ailments.  

As his primary support, he emphasizes our statement

in Myers that “[e]xpert testimony is unnecessary in cases

where a layperson can understand what caused the inju‐

ry.” 629 F.3d at 643. To illustrate the point, we noted that
6 No. 14‐2207

“when a plaintiff suffers from a broken leg or a gash

when hit by a vehicle, he doesnʹt need to produce expert

testimony.” Id. Higgins analogizes his injuries to those

mentioned in Myers, and cites to the Second Circuit’s de‐

cision in Ulfik v. Metro‐North Commuter Railroad, 77 F.3d

54 (2d Cir. 1996), which he contends underscores the apt‐

ness of his comparison. In Ulfik, the court deemed a cau‐

sation expert unnecessary for a jury to conclude that the

inhalation of paint fumes—which the plaintiff breathed

for a period of six hours while working in an under‐

ground railroad tower—caused the plaintiff to become

dizzy, resulting in his falling down a flight of stairs. Id. at

55–56 & 59. “[T]he trier of fact could reasonably deter‐

mine, without expert testimony, that prolonged exposure

to paint fumes would cause headache, nausea, and dizzi‐

ness,” the court said. Id. at 59–60. Higgins argues that

here, too, it is “obvious” that inhaling chlorine gas would

cause the injuries he suffers.  

We disagree. Unlike dizziness in the wake of extend‐

ed exposure to paint fumes or a broken leg suffered dur‐

ing a car crash, a typical layperson does not possess the

requisite knowledge to draw a causative line, without the

assistance of a medical expert, between a brief encounter

with chlorine gas and the onset of either RADS (a disease

with which, we are confident, most laypeople have no

familiarity) or asthma.  

Higgins’s reply brief insists that, even if a jury would

be unable to attribute the onset of these conditions to the

events at Holiday World, a jury is capable of concluding

that he suffered some (more minor) injury by inhaling the

fumes. (His complaint makes the general allegation that
No. 14‐2207 7

he “sustained serious personal injuries to his eyes, nose,

throat, and lungs.”)  He concedes that the causation ques‐

tion would be outside “the purview of laypeople” when

dealing with “some chemicals,” but not chlorine—a “gas

[that] is a well‐known cause of pulmonary injury,” Hig‐

gins says. Even if we were to accept that dubious conten‐

tion as true, the fact remains that the quantity of chlorine

actually inhaled by Higgins—which, recall, he encoun‐

tered some period of time after the gas was released into

the air—is entirely unknown. Hospital records from the

day of the incident describe his exposure as “mild.” And,

further complicating the causation issue, Dr. Haacke tes‐

tified in her deposition (at which she appeared in her ca‐

pacity as Higgins’s treating physician, not as his causa‐

tion expert) that Higgins is obese and that obesity affects

lung volume. Dr. Haacke also testified that there is a ge‐

netic component to asthma and that Higgins’s father suf‐

fered from emphysema. Given so much uncertainty,

there is no question that a layperson is incapable of scien‐

tifically determining specific causation here without the

assistance of an expert.   

Higgins points to two Sixth Circuit cases that he reads

as reaching conclusions that contradict the one we reach

here: Best v. Lowe’s Home Centers, Inc., 563 F.3d 171 (6th

Cir. 2009), and Gass v. Marriott Hotel Services, Inc., 558

F.3d 419 (6th Cir. 2009). Both are readily distinguishable.

In Best, the plaintiff lost his sense of smell after an open

bag of pool chemicals spilled off a store shelf and poured

directly onto his face. 563 F.3d at 174. Different from

here, though, the issue in Best was not whether the plain‐

tiff needed a causation expert to prove his case (Best had

a causation expert); rather, the issue was whether the
8 No. 14‐2207

opinion offered by Best’s causation expert was sufficient‐

ly reliable to warrant admissibility (the court concluded

that it was). Id. at 180.  

Gass (which Best mentions in passing, without opin‐

ing on its applicability) is more helpful to Higgins, but it

cannot carry the day. There, the plaintiffs suffered

“chemical poisoning” after the staff at the hotel where

they were staying filled their room with pesticide gas

while spraying for cockroaches. 558 F.3d at 422. The dis‐

trict court granted summary judgment for the hotel, be‐

cause the plaintiffs lacked a specific causation expert. Id.

But the Sixth Circuit reversed. Id. at 432. In its view, be‐

cause the plaintiffs “produced ample evidence to demon‐

strate that at least one of the chemicals Defendants rou‐

tinely used to exterminate cockroaches ... [was] capable

of causing their symptoms,” a reasonable jury, without

the existence of the expert, could find that the plaintiffs’

symptoms were caused by their exposure to the pesti‐

cides. Id.  

Gass differs from our case in several critical respects.

First, the Gass plaintiffs complained only of “chemical

poisoning” (i.e., headache, itching, dizziness, etc.). Id. at

423, 430. The connection between the inhalation of harm‐

ful pesticides—exposure to which occurred in a confined

hotel room—and those symptoms is fairly obvious, as the

Sixth Circuit found. Here, by contrast, Higgins primarily

complains that exposure to chlorine fumes caused not

symptoms, but permanent, chronic conditions—reactive

airways dysfunction syndrome and asthma. And, though

(as mentioned) he apparently also seeks damages for

other nondescript “injuries to his eyes, nose, throat, and
No. 14‐2207 9

lungs,” the causative connection Higgins asks a jury to

make in this case—which involves an undetermined

quantity of airborne chlorine, inhaled outdoors after

some unspecified interval of time following the release of

the gas—is far less apparent than the causation question

in Gass. Second, and more fundamentally, the Gass plain‐

tiffs had an expert who testified as to general causation—

that is, that pesticides are capable of causing the symp‐

toms about which the Gass plaintiffs complained. Here,

Higgins argues that no causation expert is needed, peri‐

od.

In any event, Gass applied Michigan—not Indiana—

law in reaching its conclusion. And Indiana law makes

clear that “questions of medical causation of a particular

injury are questions of science necessarily dependent on

the testimony of physicians and surgeons learned in such

matters.” Armstrong v. Cerester USA, Inc., 775 N.E.2d 360,

366 (Ind. Ct. App. 2002) (quoting Hannan v. Pest Control

Servs. Inc., 734 N.E.2d 674, 679 (Ind. Ct. App. 2000)). This

comports with our decision in Myers, where we made

clear that “when there is no obvious origin to an injury

and it has multiple potential etiologies, expert testimony

is necessary to establish causation.” 629 F.3d at 643 (cita‐

tion and internal quotation marks omitted). And that is

particularly true in a case, like the one before us, involv‐

ing an allegation that exposure to a chemical caused

permanent and debilitating lung dysfunction. Without an

expert, a plaintiff in such a complex case would be free—

as Judge Boggs warned in his dissent in Gass—to prove

his allegations relying on the logical fallacy “post hoc ergo

propter hoc” (“the fallacy of saying that because effect A

happened at some point after alleged cause B, the alleged
10 No. 14‐2207

cause was the actual cause”). 538 F.3d at 434–35. For all of

these reasons, we conclude that a causation expert is re‐

quired in this case.  

We therefore turn to an evaluation of Higgins’s con‐

tention that Dr. Haacke can serve as such an expert. Un‐

derscoring the last‐ditch nature of Higgins’s argument—

invoked only after his proposed expert, Dr. Margherita,

was deemed unqualified to testify—Higgins never dis‐

closed Dr. Haacke as an expert witness pursuant to Fed‐

eral Rule of Civil Procedure 26. Rule 26(a)(2) requires a

litigant to disclose the identity of its expert witnesses pri‐

or to trial, and, “if the witness is one retained or specially

employed to provide expert testimony,” this disclosure

must be accompanied by a written report. Fed. R. Civ. P.

26(a)(2)(A)–(B). Thus, we agree with Higgins that Dr.

Margherita would fall under that section of Rule 26,

while Dr. Haacke (Higgins’s treating physician) would

not. However, Rule 26(a)(2)(C) makes clear that, for all

expert witnesses from whom a written report is not re‐

quired (which would include Dr. Haacke), the litigant

who seeks to use that expert’s opinion testimony must

nonetheless disclose to the other party “the subject mat‐

ter on which the witness is expected to present evidence

under Federal Rule of Evidence 702, 703, or 705” and “a

summary of the facts and opinions to which the witness

is expected to testify.” Fed. R. Civ. P. 26(a)(2)(C). Such

disclosure must be made at least 90 days before the date

set for trial. Id. (D)(i). Trial was set in this case for Febru‐

ary 10, 2014. So when Koch filed its summary judgment

motion on December 19, 2013, the date for filing expert

disclosures had passed. For that reason alone, the district
No. 14‐2207 11

court would have been justified in granting summary

judgment for Koch.  

Nevertheless, we agree with the district court that,

even if Higgins had complied with his Rule 26 expert

disclosure obligations, he failed to demonstrate Dr.

Haacke’s fitness as an expert. Federal Rule of Evidence

702 permits a “witness who is qualified as an expert by

knowledge, skill, experience, training, or education” to

give testimony only if “(a) the expert’s scientific, tech‐

nical, or other specialized knowledge will help the trier

of fact to understand the evidence or to determine a fact

in issue; (b) the testimony is based on sufficient facts or

data; (c) the testimony is the product of reliable princi‐

ples or methods; and (d) the expert has reliably applied

the principles and methods to the facts of the case.” Fed.

R. Evid. 702. Rule 702 and Daubert require the district

court to determine whether proposed expert testimony is

both relevant and reliable. Zelinski v. Columbia 300, Inc.,

335 F.3d 633, 640 (7th Cir. 2003). “To gauge reliability, the

district judge must determine whether the expert is qual‐

ified in the relevant field and whether the methodology

underlying the expertʹs conclusions is reliable.” Id. In do‐

ing so, “[a] district court enjoys broad latitude both in

deciding how to determine reliability and in making the

ultimate reliability determination.” Bryant v. City of Chi‐

cago, 200 F.3d 1092, 1098 (7th Cir. 2000). In this case, the

district court deemed Dr. Haacke’s qualifications and her

methodology too questionable to permit her to testify as

an expert.  

Higgins argues that Dr. Haacke is qualified as a cau‐

sation expert by sheer virtue of her status as a pul‐
12 No. 14‐2207

monologist, which endows her with “a knowledge base

superior to a layperson.” But that’s not enough. Treating

physicians are no different than any other expert for

purposes of Rule 702; before proffering expert testimony,

they must withstand Daubert scrutiny like everyone else.

See O’Conner v. Commonwealth Edison Co., 13 F.3d 1090,

1105 n.14 (7th Cir. 1994) (“[W]e do not distinguish the

treating physician from other experts when the treating

physician is offering expert testimony regarding causa‐

tion.”). Higgins also contends that because Dr. Haacke

has twenty years of experience as a board certified pul‐

monologist, “[i]t goes without saying she understands ...

reactive airways dysfunction syndrome.” Again, Higgins

seems to misunderstand the requirements of Daubert and

Rule 702.  

As Judge Tinder articulated when he was a district

judge in the Southern District of Indiana, although a doc‐

tor may have “experience diagnosing and treating asth‐

ma ... that does not make him qualified to ‘assess its gen‐

esis.’” Cunningham v. Masterwear, Inc., 2007 WL 1164832,

at *10 (S.D. Ind. Apr. 19, 2007). Higgins, however, put

forth no evidence that Dr. Haacke has ever treated an‐

other patient for chlorine gas exposure or has any train‐

ing in toxicology. Nor has Higgins established that Dr.

Haacke employed a reliable methodology in forming her

causation opinion (even assuming she is qualified to do

so). The record demonstrates that Dr. Haacke essentially

diagnosed Higgins after listening to his own description

of his symptoms and the events at Holiday World—some

fourteen months after the fact—and after looking at the

results (though not the underlying data) of the pulmo‐

nary function study conducted by another doctor the
No. 14‐2207 13

year before. But the record is silent on whether Dr.

Haacke considered other possible causes of Higgins’s

ailments and, if so, how and why she ruled them out.

That is problematic, because Higgins told the district

court that Dr. Haacke had assessed the cause of his ail‐

ments by employing “differential diagnosis.” “Differen‐

tial diagnosis” actually refers to a method of diagnosing

an ailment, not determining its cause. See Myers, 629 F.3d

at 644. “Differential etiology,” on the other hand, is a

causation‐determining methodology. Id. But, to be valid‐

ly conducted, an expert must systematically “rule in” and

“rule out” potential causes in arriving at her ultimate

conclusion. Id. Higgins made no showing that this was

done.  

“Many times we have emphasized that expertsʹ work

is admissible only to the extent it is reasoned, uses the

methods of the discipline, and is founded on data.” Lang

v. Kohl’s Food Stores, Inc., 217 F.3d 919, 924 (7th Cir. 2000).

Here, Higgins simply failed to demonstrate this to be

true with respect to Dr. Haacke’s causation opinion. Ac‐

cordingly, we conclude that it was well within the district

court’s discretion to deem Dr. Haacke unqualified to

proffer expert testimony, even setting aside Higgins’s

non‐compliance with Rule 26.

III. Conclusion

For the foregoing reasons, we AFFIRM the district

court’s grant of summary judgment.