2022 IL App (1st) 211486
No. 1-21-1486
Opinion filed December 20, 2022
SECOND DIVISION
______________________________________________________________________________
IN THE
APPELLATE COURT OF ILLINOIS
FIRST DISTRICT
______________________________________________________________________________
DAVID MOLITOR, ) Appeal from the
) Circuit Court of
Plaintiff-Appellant, ) Cook County
)
v. ) No. 2018 L 1934
)
BNSF RAILWAY COMPANY, f/k/a Burlington Northern ) The Honorable
Santa Fe Railway Company, ) Mary Colleen Roberts,
) Judge Presiding.
Defendant-Appellee. )
PRESIDING JUSTICE FITZGERALD SMITH delivered the judgment of the court,
with opinion.
Justices Howse and Ellis concurred in the judgment and opinion.
OPINION
¶1 The plaintiff, David Molitor, appeals the trial court’s entry of summary judgment in favor of
the defendant, BNSF Railway Company, in this action under the Federal Employers’ Liability Act
(FELA) (45 U.S.C. § 51 et seq. (2018)). The trial court granted summary judgment after barring
the testimony of both of the plaintiff’s expert witnesses, Hernando R. Perez, Ph.D., and Ernest P.
Chiodo, M.D., based on the defendant’s motions asserting that their testimony failed to satisfy the
“general acceptance” test for the admission of expert testimony set forth in Frye v. United States,
293 F. 1013 (D.C. Cir. 1923) (Frye test). On appeal, the plaintiff argues that the trial court erred
No. 1-21-1486
in barring his experts’ testimony and then entering summary judgment on that basis. For the
reasons that follow, we reverse judgment of the trial court and remand for further proceedings.
¶2 I. BACKGROUND
¶3 The plaintiff was an employee of the defendant railroad from 1973 to 2014. In 2018, he filed
a one-count complaint against the defendant under FELA (45 U.S.C. § 51 et seq. (2018)), alleging
in general that, throughout his career, his job duties had required him to work in close proximity
to, or inside of, idling locomotive engines, which exposed him on a daily basis to various toxic
substances and carcinogens. The complaint alleged that his exposure to these substances over
many years caused, in whole or part, his development of B-cell lymphoma, diagnosed in 2015. It
alleged that, before and during the plaintiff’s employment, the defendant knew of evidence
demonstrating a positive correlation or causative link between the exposure to these toxic
substances and carcinogens and the development of cancer. It alleged various ways in which the
defendant was negligent in allowing the plaintiff’s exposure to these cancer-causing substances.
Additionally, although apparently not pled in the complaint, the plaintiff later testified that he was
exposed throughout his career to herbicides, specifically Roundup, that were sprayed in the rail
yards where he worked to control weed growth.
¶4 Discovery progressed, and the plaintiff ultimately disclosed two controlled expert witnesses
to testify on his behalf. His liability expert was Dr. Perez, an industrial hygienist. His medical
causation expert was Dr. Chiodo, an internal medicine physician who is also a licensed attorney
and has various additional credentials. The defendant filed motions to bar the admission of the
testimony of both of these experts on the basis that their testimony failed the Frye test. The trial
court granted both motions, barred the testimony of both experts in their entirety, and entered
summary judgment in the defendant’s favor. We take the two experts in turn, addressing their
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opinions and testimony and the basis upon which their testimony was barred.
¶5 A. Dr. Perez
¶6 Dr. Perez is an expert in the fields of industrial hygiene and occupational health who
evaluated and expressed opinions about the plaintiff’s working conditions during his employment
with the defendant, specifically his exposure to diesel exhaust and herbicides. Dr. Perez holds a
Ph.D. in industrial hygiene from Purdue University and a Master of Public Health degree in
environmental and occupational health from Emory University. He is certified in the
comprehensive practice of industrial hygiene by the American Board of Industrial Hygiene and in
the practice of safety by the Board of Certified Safety Professionals. Since 2015 he has been
employed by the United States Citizenship and Immigration Services, part of the United States
Department of Homeland Security, as its lead industrial hygienist and environmental hygiene
program manager. In that capacity, he is the environmental and occupational health technical
expert for the agency and is responsible for coordination and performance of industrial hygiene
activities at its facilities across the country. Prior to that, he was employed as full-time faculty at
the Drexel University School of Public Health from 2004 to 2014 and was director of its industrial
hygiene consulting service from 2006 to 2014.
¶7 To reach his opinions in this case, Dr. Perez conducted an interview with the plaintiff and
reviewed the plaintiff’s deposition. He also reviewed various discovery materials produced by the
defendant concerning diesel exhaust exposure levels to employees, including a 1997 presentation
addressing the potential dangers of exposure to diesel locomotive exhaust, exposure levels, its risk
as a human carcinogen, and steps to protect employees from diesel exhaust exposure. He also
conducted a review of pertinent literature and the websites of various government agencies and
organizations involving environmental issues and cancer research. Among the literature upon
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which he particularly relied was a study by lead author Dr. Anjoeka Pronk, a research scientist at
the National Cancer Institute of the National Institutes of Health. That study researched diesel
exhaust exposure levels in occupational environments in which diesel engine use is common.
¶8 Dr. Perez’s report states that the plaintiff “experienced chronic occupational diesel exhaust
exposure during the forty-one (41) year period between 1973 and 2014.” Dr. Perez relied on the
fact that, from 1973 until 2003, the plaintiff’s primary job duties involved switching train cars and
making up trains at various local industry sites. From 1973 until 1993, the plaintiff worked as a
yard switchman/brakeman. In 1993, he was promoted to conductor and continued performing
switching duties and working switcher routes until 2003. He relied on the plaintiff’s explanation
that his job duties during this time involved either riding on, being on the ground directly adjacent
to, or being in close proximity to idling or transiting switcher locomotives. He also relied upon the
plaintiff’s explanation that, between 1973 and the late 1980s, 95% of the locomotives used were
older, high-emitting locomotives with cab environments that allowed for built-up concentrations
of diesel exhaust. Dr. Perez explained that this statement by the plaintiff concerning these older,
heavy-emitting locomotives was corroborated by the defendant’s internal correspondence from
1996. In 2003, the plaintiff transitioned to the role of yardmaster, in which he spent the majority
of his time indoors in an office environment, which continued until 2007. In 2008, he returned to
work as a conductor and continued in that position until his retirement in 2014.
¶9 Dr. Perez expressed opinions that, between 1973 and approximately 1988 (while the older,
heavy-emitting locomotives were in use), the plaintiff’s average exposure to diesel exhaust was
“consistent with the upper quartile of the low range, with frequent excursions into the intermediate
range and occasional excursions into the high range.” (These references to “ranges” pertained to
the three ranges of elemental carbon exposure—which is an established surrogate for diesel
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No. 1-21-1486
exhaust exposure—used by Dr. Pronk’s team in its research of occupational exposures to diesel
exhaust: low was less than 25 micrograms per square meter, intermediate was less than 50
micrograms per square meter, and high was between 27-658 micrograms per square meter.) Dr.
Perez also explained that, between 1989 and 2003, the plaintiff’s exposures were “consistent with
the low range, with occasional excursions into the intermediate range.” Between 2004 and 2007,
the plaintiff’s exposures were “consistent with ambient background concentrations, with
occasional exposures into the low range.” Between 2008 and 2014, the plaintiff’s exposures were
“consistent with the low range.” Dr. Perez noted that these average exposure levels were also
consistent with the typical exposure levels in railroad settings that had been documented in the
defendant’s training presentation from 1997, which indicated that levels of exhaust ranged up to
about 47 micrograms per square meter. Dr. Perez stated that the plaintiff’s locomotive cab
environment would have exceeded these typical levels where visible buildup of exhaust had
occurred. Dr. Perez further explained that the plaintiff’s work settings were representative of
environments associated with the elevated risk of occupationally related cancer.
¶ 10 Regarding the plaintiff’s exposure to herbicides, Dr. Perez relied on the plaintiff’s
explanation that, at the railyard where he worked, large-scale spraying of herbicides had occurred
one to two times per year over the course of his career. The plaintiff had explained that he was
required to come into physical contact with visibly contaminated surfaces, such as switch handles,
while performing his work after spraying had occurred. The plaintiff also described experiencing
skin exposure to herbicide residue. He stated that he had once worked twelve hours on a spray-
train from which Roundup was being sprayed along the tracks and he could smell the sprayed
herbicide his entire shift.
¶ 11 Dr. Perez explained that several methods exist for estimating historical occupational
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exposures when objective and specific measurement data are nonexistent. He stated, however, that
expert assessment by industrial hygienists is considered the most accurate method for assessing
chemical exposures in studies requiring this type of evaluation. He explained that the usefulness
of this methodology has been documented for decades, citing a 1989 study establishing that
“ ‘[i]ndustrial hygienists were able to give remarkably accurate subjective estimates of the mean
exposure without historical data and even better estimates with the data.’ ” 1 Dr. Perez stated that
this type of expert assessment was what he had done in this case. He stated, “Through the collection
of a job task history including specific information regarding determinations of exposure, [the
plaintiff’s] historical exposure conditions were assessed and reported within the context of the
framework documented by Pronk et al.”
¶ 12 Finally, Dr. Perez explained that, at the time the plaintiff began his career in 1973, the railroad
industry was aware of several of the health risks that diesel exhaust exposure posed to employees.
Among other things, he references railroad industry documentation from 1955 recognizing the
carcinogenic potential of diesel exhaust exposure. He also referenced the defendant’s 1997 training
presentation concerning the health claims associated with diesel exhaust exposure among workers.
¶ 13 Based on the above, Dr. Perez expressed opinions that the defendant was negligent, among
other things, in failing to provide adequate air monitoring or to otherwise determine the plaintiff’s
level of exposure to diesel exhaust or herbicides, failing to provide him with adequate training and
equipment to prevent or lessen his exposure, failing to implement controls to reduce or prevent his
exposure, and failing to provide him with adequate warnings, training, and information about the
hazards of exposure.
1
Neil C. Hawkins & John S. Evans, Subjective Estimation of Toluene Exposures: A Calibration
Study of Industrial Hygienists, 4 Applied Indus. Hygiene 61, 61 (1989).
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¶ 14 At his discovery deposition, Dr. Perez further explained the methodology that he used to
understand the plaintiff’s past exposure to diesel exhaust and herbicides in his work environment.
He explained that the method was called historical (or reconstructed) exposure assessment. It is a
method that has been relied upon in industrial hygiene “for an extended period of time” and is
“established in the literature.” He explained his process as follows:
“The first step is to obtain—so I reviewed industrial hygiene data from railroad
environments provided by railroads in the peer-reviewed literature, etc., a large number of
individual pieces of data. That knowledge, that understanding, that review with that
assessment I went through the process of collecting an exposure history—a job history—
for Mr. Molitor through our conversation. Through that process, I identified the sources of
exposure, the pathways for the containment to reach his breathing zone specifically,
because we’re talking specifically about inhalation exposures here, with diesel exhaust,
with insecticide, with herbicides … there may have been exposure but the primary
exposure with diesel exhaust would have been inhalation, and given the nature of
enclosures of his environments, the proximity to sources, his description of the nature of
the source itself relative to others that he has experienced over the course of his career and
… combining with my industrial hygiene experience and understanding of exposure in
workplace settings to determine where he lies in the context of that framework provided
by Pronk.”
He testified that, in the field of industrial hygiene, “there are many instances during which we need
to evaluate exposures for which there’s no objective data. … And in order to do that, we need to
go back and reconstruct the exposures to these individuals, and this is how we do it.”
¶ 15 In its motion to exclude the opinions and testimony of Dr. Perez, the defendant argued that
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his opinions had not been shown to be “based upon generally accepted principles or sufficiently
reliable so as to be admitted.” It argued that Dr. Perez’s only case-specific knowledge was a
conversation with the plaintiff. Accordingly, Dr. Perez was unaware of facts such as the size of
the locomotive with which the plaintiff worked, its manufacturer, the plaintiff’s proximity to the
source of diesel exhaust while performing job duties, the model of the locomotive or engine the
plaintiff worked with between 1989-2003, the difference in the size and fuel efficiency of a
switcher engine and regular locomotive, or whether switcher engines were less powerful than
regular freight locomotives. The defendant’s motion further asserted that Illinois law requires that
“an expert witness must quantify the specific level of exposure to environmental chemicals in order
to be admissible” and that an expert “cannot rely solely on a lay person’s statements or testimony.”
The motion argued that it was “frankly unclear what method, if any, Perez employed to arrive at
his opinions in this case,” as he relied on “scant literature” and “limited independent knowledge
of and experience with diesel exhaust analysis and testing procedures from which to draw upon.”
The defendant’s motion was not supported by the affidavit of any expert witness.
¶ 16 In response, the plaintiff argued that the methodology by which Dr. Perez had assessed the
plaintiff’s historical exposures to diesel exhaust and herbicide was not new or novel and, therefore,
it was not subject to a Frye test. Rather, it was generally accepted within the field of industrial
hygiene and was identical to the methodology used by the defendant’s own expert, Dr. Dallas
Cowan. He cited Dr. Cowan’s description of his own process for assessing the plaintiff’s levels of
past exposures was to review the plaintiff own testimony to “understand his job title, the types of
duties that he conducted, the distance that he would have been from a point source of diesel
exhaust, and then compare that with the peer-reviewed literature to understand the breadth of the
scientific understanding of air concentrations in various workplace settings.”
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¶ 17 The trial court conducted a hearing. The hearing consisted entirely of attorney argument, with
no testimony being given with respect to the motions. The trial court then issued a written order
barring the testimony by Dr. Perez. Stating that a trial court must “look behind the expert’s
conclusions and analyze the adequacy of their foundation,” the trial court found that Dr. Perez’s
opinions must be entirely barred for the reason that they lacked the necessary foundation for the
court to determine whether they were based upon a methodology or principle that was generally
accepted by the scientific community. The trial court found that Dr. Perez’s opinions were not
based on sufficient facts or data, but instead were based upon his conversations with the plaintiff
in which he recounted his experience with diesel fumes and herbicides during the time he worked
for the railroad. The court stated,
“Perez admits he never went to any of the sites Molitor worked nor did he even consider
factors that may be relevant to the formation of his opinions. Not considering these factors
among other relevant data and relying instead on Molitor for facts he determined salient
does not form a sufficient basis for his opinions.”
¶ 18 C. Dr. Chiodo
¶ 19 Dr. Chiodo is a board-certified internal medicine and occupational medicine physician. In
addition to his medical degree from Wayne State University School of Medicine, he holds a master
of public health degree from Harvard University, a master of science in biomedical engineering
from Wayne State University, a master of science in threat response management from the
University of Chicago, a master of science in occupational and environmental health science with
specialization in industrial toxicology from Wayne State University, and a master of science in
evidence-based health care from the University of Oxford. He is also a licensed attorney. He is
certified by the American Board of Industrial Hygiene as a certified industrial hygienist. He has
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served as an assistant clinical professor of internal medicine, family medicine, and public health
at Wayne State University School of Medicine and an assistant adjunct professor of industrial
hygiene and toxicology at Wayne State University. He has also served as the medical director and
manager of medical and public health services for the City of Detroit.
¶ 20 To reach his opinions in this case, Dr. Chiodo reviewed the complaint, the discovery
depositions of the plaintiff and one of his treating physicians, the plaintiff’s written discovery
responses, the plaintiff’s medical records, and the report of Dr. Perez. Dr. Chiodo’s report notes
that the plaintiff was born in 1954 and worked for BNSF from 1973 to 2008 as a
switchman/brakeman, train conductor, and yard master. He also had a history of smoking. He had
been diagnosed with diffuse B-cell lymphoma, a form of non-Hodgkin’s lymphoma. He noted that
Dr. Perez’s report had indicated that it was his opinion that the plaintiff had exposure to diesel
exhaust and herbicides during the course of his employment.
¶ 21 Dr. Chiodo’s report then states, “Exposure to diesel exhaust is well known to cause
lymphoma.” It then sets forth the citation and abstract of a 2008 article by lead author Chandima
P. Karunanayake, which studied the association between non-Hodgkin’s lymphoma and
occupational exposures related to long-held occupations. In pertinent part, the report identifies the
results of that study to be that “constant exposure to diesel exhaust fumes” was one of the factors
that “independently increased the risk of [non-Hodgkin’s lymphoma].” The report also states that
the article concluded, in pertinent part, that “[a]n increased risk of developing [non-Hodgkin’s
lymphoma] is associated with … exposure to diesel fumes.”
¶ 22 Dr. Chiodo’s report goes on to state, “Exposure to herbicides is known to cause lymphoma.”
It then gives the citation and abstract to a 2014 article by lead author Leah Schinasi, which
described the results of a systematic review and series of meta-analyses from nearly three decades
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of epidemiologic research on the relationship between non-Hodgkin’s lymphoma and occupational
exposure to agricultural pesticide active ingredients and chemical groups. It states in part that “B
cell lymphoma was positively associated with phenoxy herbicides and the organophosphorus
herbicide glyphosate. Diffuse large B-cell lymphoma was positively associated with phenoxy
herbicide exposure.”
¶ 23 Dr. Chiodo’s report concludes with his opinion to a reasonable degree of medical and
scientific certainty “that the exposures to diesel exhaust and herbicides experienced by Mr. David
Molitor during the course of his railroad employment were a significant cause of his development
of Diffuse B-Cell Lymphoma.”
¶ 24 In his discovery deposition, Dr. Chiodo testified multiple times that his opinions were not
predicated on the articles he cited or on a search of the medical or scientific literature. Rather, he
explained that he had known for a long time as a result of his training, education, and experience
that diesel exhaust and herbicides were known causes of non-Hodgkin’s lymphoma. He stated that
he found the two articles and cited them to corroborate his opinion, but his opinion was not based
on these articles. He testified that he found that the 2008 Karunanayake article corroborated his
opinion at a 95% or greater probability level that diesel exhaust causes non-Hodgkin’s lymphoma.
He acknowledged that the article only used the word “association” with respect to diesel exhaust
and non-Hodgkin’s lymphoma, not “causation,” but he testified that the word causation is a term
that is rarely used in scientific articles. He explained, however, that despite its word usage, the
article expressed its conclusions at a level of 95% probability that the results did not occur by
random chance. He testified that he was not aware of any literature saying that the association of
diesel exhaust with non-Hodgkin’s lymphoma is due to some “confounder” or “confounding”
effect, and thus he believes that it is a causal relationship.
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¶ 25 While Dr. Chiodo was initially unaware during his testimony of what herbicides the plaintiff
had been exposed to, his recollection was ultimately refreshed that the plaintiff had testified in his
deposition that Roundup was used in his work environment. He then explained that the plaintiff
had thus been exposed to glyphosates, which is a type of herbicide known to cause non-Hodgkin’s
lymphoma.
¶ 26 He testified that from a medical and toxicology standpoint, there was no threshold level of
diesel exhaust or herbicide exposure below which it had no carcinogenic effect or could not cause
B-cell non-Hodgkin’s lymphoma. His understanding, however, was that the plaintiff, while
working in a railyard, had been exposed to diesel exhaust and herbicides far greater than what the
typical person would be exposed to in everyday life.
¶ 27 He testified multiple times that he “could” extrapolate from the fact that diesel exhaust was
well-known to cause lung cancer that it could also cause other cancers, such as non-Hodgkin’s
lymphoma. He testified that if a person breathes in a chemical known to cause lung cancer, given
the absorption into the blood that would occur, the same cancer-causing transformations would
occur in the hematopoietic system that causes cancer in the lungs. He reiterated multiple times,
however, that he did not have to extrapolate because he had articles directly on point confirming
that non-Hodgkin’s lymphoma is caused by diesel exhaust.
¶ 28 In its motion to exclude the testimony and opinions of Dr. Chiodo, the defendant argued that
his opinions “were not rooted in generally accepted principles by medical causation experts.” The
defendant argued that Dr. Chiodo had improperly formed his opinion first, and only then sought
out articles corroborating his opinion, without also searching for negative articles. It argued that
his opinions were based on only two studies, and these studies referred only to an “association”
between diesel exhaust and herbicides and B-cell lymphoma, not causation. The defendant then
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argued that several recent federal court decisions rejected the notion that association and causation
were the same. Finally, it argued that his extrapolation opinions were unsound, unfounded, and
not generally accepted.
¶ 29 In response, the plaintiff argued that Dr. Chiodo used a reasoned and appropriate analysis to
reach his opinions. He argued that Dr. Chiodo had reviewed the pertinent record in this case and
applied his unique combination of training and experience to reach an opinion, which he then
corroborated by citing peer-reviewed medical literature. The plaintiff argued that Dr. Chiodo had
adequately explained why the use of the word “association,” and not “causation,” in his cited
studies did not mean that those studies were unsupportive of the conclusion of a causative
relationship between diesel exhaust and herbicides and non-Hodgkin’s lymphoma. The plaintiff
argued that the defendant was relying on inapposite case law applying the federal standard for the
admission of testimony, not the Frye standard used in Illinois. He argued that Dr. Chiodo had taken
the relevant facts of the plaintiff’s case into consideration in forming his opinion and that any facts
he did not consider went only to the weight to be given to his testimony, not its admissibility.
¶ 30 The trial court granted the defendant’s motion to bar Dr. Chiodo’s testimony. As it had done
with Dr. Perez, the trial court first concluded that it must look behind Dr. Chiodo’s opinions to
what he had based those opinions on. The trial court then stated that neither of the two published
studies upon which Dr. Chiodo relied supported his assertion that exposure to diesel exhaust or
herbicides causes B-cell lymphoma. Instead, the trial court reasoned, those studies “claim there
may be evidence of a positive ‘association with’ B-Cell Lymphoma.” The court found that Dr.
Chiodo had cited no scientific authority for his assertion that association essentially means causes
if there is no confounder stated. The trial court further found that Dr. Chiodo had relied upon the
extrapolation principle and then stated that neither the plaintiff nor Dr. Chiodo had provided
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scientific evidence that the method Dr. Chiodo employed to reach his conclusions was generally
accepted in the field of medical causation.
¶ 31 C. Summary Judgment
¶ 32 The trial court then concluded that, based upon its determination that the opinion evidence of
Dr. Perez and Dr. Chiodo were inadmissible, the plaintiff would be unable to prove that any
purported negligence on the part of the defendant medically caused or contributed to his
development of B-cell lymphoma. Without evidence necessary to prove all elements of his claim,
the trial court concluded that the defendant was entitled to summary judgment. The plaintiff
thereafter filed a motion to reconsider, which the trial court denied. The plaintiff then filed a timely
notice of appeal.
¶ 33 II. ANALYSIS
¶ 34 On appeal, the plaintiff argues that the trial court erred in granting summary judgment in
favor of the defendant because the opinions of Dr. Perez and Dr. Chiodo satisfied the Frye test and
should not have been barred.
¶ 35 A. Legal Standards
¶ 36 We begin by setting forth the legal standards pertinent to this appeal. As an appeal coming
before this court on the trial court’s granting of summary judgment in favor of the defendant, our
review is de novo. Walker v. Chasteen, 2021 IL 126086, ¶ 13. A motion for summary judgment
should be granted where the pleadings, depositions, and admissions on file, together with any
affidavits, show that there is no genuine issue as to any material fact and that the moving party is
clearly entitled to judgment as a matter of law. 735 ILCS 5/2-1005(c) (West 2020). Where it is
determined that a plaintiff cannot establish a necessary element of his cause of action, summary
judgment is proper. Bagent v. Blessing Care Corp., 224 Ill. 2d 154, 163 (2007).
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¶ 37 We deal here with an action under the FELA. The FELA is a federal law providing that a
common carrier by railroad shall be liable in damages for an employee’s “injury or death resulting
in whole or in part from the negligence of any of the officers, agents, or employees of such carrier.”
45 U.S.C. § 51 (2018). It was enacted in 1908 to provide a federal remedy for railroad workers
who suffer personal injuries as a result of the negligence of their employer. Atchison, Topeka &
Santa Fe Ry. Co. v. Buell, 480 U.S. 557, 561 (1987). It eliminates a number of traditional defenses
to tort liability to facilitate recovery in meritorious cases. Id. It is recognized as a broad remedial
statute that is to be liberally construed to accomplish the objectives of Congress. Id. at 562.
¶ 38 Given these goals and the language of the statute, it has been recognized that “in comparison
to tort litigation at common law, ‘a relaxed standard of causation applies under FELA.’ ” CSX
Transportation, Inc. v. McBride, 564 U.S. 685, 691-92 (2011) (quoting Consolidated Rail Corp.
v. Gottshall, 512 U.S. 532, 542-43 (1994)). The FELA does not incorporate “proximate cause”
standards used in nonstatutory common law tort actions. Id. at 688 (citing Rogers v. Missouri
Pacific R.R. Co., 352 U.S. 500 (1957)). Rather, the test “ ‘is simply whether the proofs justify with
reason the conclusion that employer negligence played any part, even the slightest, in producing
the injury or death for which damages are sought.’ ” Id. at 692 (quoting Rogers,
352 U.S. at 506).
¶ 39 Where an action under the FELA is brought in state court, questions concerning the
admissibility of evidence are governed by state law. Noakes v. National R.R. Passenger Corp., 363
Ill. App. 3d 851, 854 (2006). Accordingly, in an action under the FELA in Illinois, the Frye test is
the standard exclusively used to determine the admission of expert testimony. Id. at 854-55; see
Donaldson v. Central Illinois Public Service Co., 199 Ill. 2d 63, 76-77 (2002), abrogated in part
on other grounds by, In re Commitment of Simons, 213 Ill. 2d 523 (2004); In re Detention of New,
2014 IL 116306, ¶ 25. “The Frye standard, commonly called the ‘general acceptance’ test, dictates
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that scientific evidence is only admissible at trial if the methodology or scientific principle upon
which the opinion is based is ‘sufficiently established to have gained general acceptance in the
particular field in which it belongs.’ ” Donaldson, 199 Ill. 2d at 77 (quoting Frye,
293 F. at 1014).
The Frye test has now been codified in the second sentence of Illinois Rule of Evidence 702 (eff.
Jan. 1, 2011):
“Where an expert witness testifies to an opinion based on a new or novel scientific
methodology or principle, the proponent of the opinion has the burden of showing the
methodology or scientific principle on which the opinion is based is sufficiently established
to have gained general acceptance in the particular field in which it belongs.”
¶ 40 Several important considerations are involved in applying the Frye test. First, “general
acceptance” does not concern the ultimate conclusion that the expert reached. Donaldson, 199 Ill.
2d at 77. Rather, the focus is the underlying methodology that the expert used to generate the
conclusion. Id. If the underlying method that the expert used to generate his or her opinion is
reasonably relied upon by experts in the pertinent scientific field, then the factfinder may consider
the opinion, regardless of the novelty of the conclusion reached. Id.
¶ 41 Second, general acceptance does not mean universal acceptance.
Id. It does not require that
the methodology be accepted by unanimity, consensus, or even a majority of experts. Id. at 78. A
methodology is not generally accepted, however, if it experimental or of dubious validity. Id. The
Frye standard is meant to exclude methods new to science that undeservedly create a perception
of certainty when the basis for the evidence or opinion is actually invalid. Id.
¶ 42 Third, the Frye standard does not make the trial judge a “gatekeeper” of all expert opinion
testimony. Id. Rather, a trial judge may apply the Frye test only if the methodology or scientific
principle offered by the expert to support his or her conclusions is “new” or “novel.” Id. at 78-79.
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While identifying whether a scientific technique is new or novel is not always easy, one will meet
this standard if it is “ ‘original or striking’ or does ‘not resembl[e] something formerly known or
used.’ ” Id. at 79 (quoting Webster’s Third New International Dictionary 1546 (1993)). Also, the
Frye standard is applied only to “scientific” evidence, which is evidence that is “the product of
scientific tests or studies.” People v. McKown, 226 Ill. 2d 245, 254 (2007).
¶ 43 Fourth, the supreme court has rejected the notion that Illinois uses a “Frye-plus-reliability”
standard. Donaldson, 199 Ill. 2d at 81. In other words, a Frye test does not involve a component
by which the trial court, after determining whether a technique or methodology is generally
accepted, also inquires into whether the expert’s opinion is “reliable.” Id. at 80-81; see also Simons,
213 Ill. 2d at 532 (“Under the Frye standard, the trial court is not asked to determine the validity
of a particular scientific technique.”); In re Commitment of Sandry, 367 Ill. App. 3d 949, 966
(2006) (“inquiry into the validity or reliability of a methodology is outside the scope of the Frye
test”). Rather, questions concerning the underlying data upon which the expert relied go to the
weight of the evidence, not its admissibility. Donaldson, 199 Ill. 2d at 81. Questions concerning
an expert’s application of generally accepted techniques likewise go to the weight of the evidence,
not admissibility. Id.
¶ 44 Finally, exclusion of testimony through the general acceptance test must not be used as a
substitute for an attorney’s traditional methods of advocacy in exposing shaky but admissible
evidence through vigorous cross-examination and the presentation of contrary evidence at trial. Id.
at 88.
¶ 45 The proponent may prove general acceptance of a particular methodology by pointing to
scientific publications, prior judicial decisions, practical applications, and the testimony of
scientists about the attitudes of their fellow scientists. Mitchell v. Palos Community Hospital, 317
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Ill. App. 3d 754, 762 (2000). A trial court’s Frye analysis is subject to de novo review. Simons,
213 Ill. 2d at 530-31. In conducting such a de novo review, the reviewing court may similarly
consider not only the trial court record but also, where appropriate, sources outside the record,
such as legal and scientific articles and court opinions from other jurisdictions. Id. at 531.
¶ 46 B. Dr. Perez
¶ 47 As explained in the background above, the trial court barred Dr. Perez’s entire testimony
based upon its determination that it must “ ‘look behind the expert’s conclusion[s] and analyze the
adequacy of the[ir] foundation,’ ” quoting Soto v. Gaytan, 313 Ill. App. 3d 137, 146 (2000). Upon
doing so, the trial court concluded that the opinions expressed by Dr. Perez “lack a reliable
foundation, that is, they are not based on sufficient facts or data.” Instead, the trial court reasoned,
Dr. Perez’s opinions were based on his conversation with the plaintiff recounting his experience
with diesel fumes and herbicides during his years working for the defendant. The court noted that
Dr. Perez did not go to any of the sites where the plaintiff had worked, “nor did he even consider
factors that may be relevant to the formation of his opinions.” The trial court determined that the
opinions of Dr. Perez lacked the necessary foundation for the court to determine whether they were
based on a methodology that was generally accepted by the scientific community, and therefore it
barred their admission at trial.
¶ 48 On appeal, the plaintiff argues that the trial court misapplied the Frye standard by first
considering whether his testimony had a sufficient foundation for the conclusions he reached. He
argues that the Frye test does not include analyzing the factual basis for an expert’s opinion, which
goes only to the weight of the testimony, not its admissibility. He notes that Soto, the case relied
upon by the trial court, did not involve a Frye test. Instead, Soto involved whether a plaintiff’s
treating physician could express an opinion about the permanency of the plaintiff’s injury in the
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No. 1-21-1486
absence of a recent examination of the plaintiff prior to trial. See id. at 139. The majority in Soto
cited Frye as support for the proposition that a trial court acts as the “gatekeeper” of proposed
opinion evidence that a jury may hear. Id. at 146. Then, in what was clearly dicta, the majority
went on to state that “[p]ursuant to Frye, the trial court closely examines proposed opinion
testimony from a scientific expert to determine whether it bears sufficient indicia of reliability to
submit to the jury.” Id. It stated that as gatekeeper, “the trial court plays a critical role in excluding
testimony that does not bear an adequate foundation of reliability.” Id. at 147. The plaintiff here
points out that Soto was decided two years prior to Donaldson, which clarified that the Frye test
did not involve any analysis into the “reliability” of an expert’s methodology or conclusions and
that questions concerning underlying data goes to the weight, not the admissibility, of evidence.
¶ 49 In response, the defendant points out that since Donaldson, decisions of this court have
continued to state that a trial court’s role is to examine the reliability of proposed scientific opinion
testimony before allowing a jury to hear it. See, e.g., Poliszczuk v. Winkler, 387 Ill. App. 3d 474,
495 (2008) (“Pursuant to Frye … the trial court closely examines proposed opinion testimony
from a scientific expert to determine whether it bears sufficient indicia of reliability before the
testimony is submitted to the jury.” (citing Soto, 313 Ill. App. 3d at 146-47)); Roach v. Union
Pacific R.R., 2014 IL App (1st) 132015, ¶ 55 (citing Soto for the proposition that a trial court acts
as “ ‘gatekeeper’ allowing through only reliable and relevant evidence for consideration by the
jury”); Bangaly v. Baggiani, 2014 IL App (1st) 123760, ¶ 155 (citing Soto for the proposition that
one of the trial court’s focuses in determining whether to allow expert testimony is that “the
testimony must be reliable and have a proper basis for the opinion to meet foundational
requirements”); People v. Safford, 392 Ill. App. 3d 212, 221 (2009) (citing Soto for the proposition
that admission of expert testimony requires the proponent to lay an adequate foundation
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No. 1-21-1486
“ ‘establishing that the information upon which the expert bases his opinion is reliable’ ” (quoting
Hiscott v. Peters, 324 Ill. App. 3d 114, 122 (2001), citing Soto,
313 Ill. App. 3d at 146)).
¶ 50 Several points must be made about the cases cited by the defendant. First, none of these cases
cited by the defendant involved a Frye test. Thus, none of these statements concerning the trial
court’s examination of the “reliability” of proposed expert testimony actually occurred in the
context of a Frye analysis. Both Poliszcuk and Roach involved issues about whether physicians
could express medical causation opinions in the absence of a recent examination of the plaintiff.
Poliszczuk, 387 Ill. App. 3d at 495-96; Roach,
2014 IL App (1st) 132015, ¶¶ 61-65. Bangaly
addressed the trial court’s decisions about whether to allow an attorney and a political science
professor to give testimony on the validity of a marriage under the law of the country of Mali.
Bangaly, 2014 IL App (1st) 123760, ¶¶ 158-71. In Safford, the issue was whether the trial court
erred in allowing an expert in fingerprint examination to testify without explaining the evidentiary
foundation for his conclusion. Safford, 392 Ill. App. 3d at 219. None of these issues are subjects
for a Frye test, and, thus, none of these cases support the proposition that a trial court analyzes the
reliability of the factual foundation of an expert’s testimony as a component of the Frye test.
¶ 51 Second, when our cases cite the principle that a trial court must ensure that an adequate
foundation has been established that the information upon which an expert bases his or her opinion
is “reliable,” this refers to the requirement of ensuring that the facts or data upon which the expert
has based his or her opinion is “of a type reasonably relied upon by experts in the particular field
in forming opinions or inferences upon the subject.” Ill. R. Evid. 703 (eff. Jan. 1, 2011); see People
v. Simmons, 2016 IL App (1st) 131300, ¶¶ 115, 124 (citing City of Chicago v. Anthony,
136 Ill. 2d
169, 186 (1990)); Wilson v. Clark,
84 Ill. 2d 186, 193 (1981) (“the key element in applying Federal
Rule 703 is whether the information upon which the expert bases his opinion is of a type that is
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No. 1-21-1486
reliable”). The reference to “reliability” under this principle does not refer to whether an expert
has set forth sufficiently detailed reasons for his or her opinions. Simmons, 2016 IL App (1st)
131300, ¶ 124.
¶ 52 We reiterate that it is not part of the Frye test for a trial court to examine the “reliability” or
“validity” of the underlying data on which an expert’s opinion is based. See Donaldson, 199 Ill.
2d at 81 (“the Frye-plus-reliability test impermissibly examines the data from which the opinion
flows”). The test is exclusively whether the scientific methodology or principle is generally
accepted in the particular scientific field in which it belongs. Id. at 77. It is unclear from the trial
court’s order whether the court was intending to analyze the reliability of the factual foundation
for Dr. Perez’s opinions as part of its Frye analysis, or whether it was making a preliminary inquiry
prior to applying the Frye test. See Northern Trust Co. v. Burandt & Armbrust, LLP, 403 Ill. App.
3d 260, 278 (2010) (describing a Frye determination as a “threshold matter” and holding opinion
evidence satisfying Frye may nevertheless be excluded for lack of an evidentiary foundation).
¶ 53 Thus, we will consider the trial court’s analysis as a pre-Frye test preliminary inquiry into
whether the opinions of Dr. Perez were so deficient in their factual foundation that his testimony
must be stricken in its entirety. In doing so, we recognize that the factual basis for a witness’
opinion is a matter generally held to go to the weight of the evidence, not its admissibility. Snelson
v. Kamm, 204 Ill. 2d 1, 26-27 (2003). The information used or not used by an expert is generally
not a sufficient reason to bar an expert’s testimony as lacking foundation. Noakes, 363 Ill. App.
3d at 858-59 (citing Turner v. Williams,
326 Ill. App. 3d 541, 555 (2001)). Also, “ ‘[g]reat liberality
is allowed the expert in determining the basis of his opinions.’ ” Swartz v. Sears, Roebuck & Co.,
264 Ill. App. 3d 254, 276 (1993) (quoting Melecosky v. McCarthy Brothers Co.,
115 Ill. 2d 209,
216 (1986)); Jackson v. Seib,
372 Ill. App. 3d 1061, 1072 (2007). It is presumed that the special
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No. 1-21-1486
knowledge that experts possess gives them the ability to judge the reliability of the information
upon which they base their opinions. Swartz, 264 Ill. App. 3d at 276. That said, an expert witness
cannot base an opinion on mere conjecture or guess. Dyback v. Weber, 114 Ill. 2d 232, 244 (1986).
¶ 54 As stated above, the principal reason cited by the trial court for its conclusion that Dr. Perez’s
opinions were not based on sufficient facts or data was the fact that his opinions were based upon
a conversation with the plaintiff in which he recounted his experience with diesel fumes and
herbicides while working for the defendant. On appeal, the defendant likewise characterizes Dr.
Perez’s opinions as unreliable and lacking foundation because his assessment of the plaintiff’s
exposures “was gleaned solely from plaintiff’s description in conversations that occurred decades
after exposure.” However, the fact that an expert’s opinion is based upon information received
from an interested litigant is generally considered relevant only to the weight that it should be
given, not to its admissibility. Peach v. McGovern, 2019 IL 123156, ¶ 54 (citing J.L. Simmons Co.
ex rel. Hartford Insurance Group v. Firestone Tire & Rubber Co., 108 Ill. 2d 106, 117 (1985)).
¶ 55 The defendant further contends on appeal that the speculative nature of Dr. Perez’s analysis
is shown by his testimony that he was unable to identify from the data any clear pattern indicating
that the age of an engine affected its emission levels or exposure to those working on or near it
because that depended also on how well the engine had been maintained and whether it had any
faulty systems. It asserts that Dr. Perez admitted during his deposition that he had only speculated
that the smaller switcher engines that the plaintiff used between 1973 and 1988 were worn out and
exposed to higher levels of exhaust. And it asserts that he testified that he did nothing to research
the difference between emissions from a freight locomotive and a switcher engine and that he did
not know the make or model of the locomotive used by the defendant between 1973-1988, the size
of the engine in a BNSF switcher locomotive, or the fuel efficiency of the engine at issue.
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No. 1-21-1486
¶ 56 Furthermore, the defendant criticizes Dr. Perez for not using the results of the defendant’s
own diesel exhaust and pesticide studies in his analysis, although Dr. Perez testified in his
deposition that he disputed the accuracy of the defendant’s internal studies on the issue. The
defendant asserts that Dr. Perez thus ignored the available data and instead accepted the plaintiff’s
“self-serving testimony” and reached conclusions that were unsupported by the railroad testing
and the Pronk framework. According to the defendant, the Pronk study actually concluded that
trainmen in situations similar to the plaintiff were exposed only to “low levels of diesel exhaust.”
¶ 57 We hold that an adequate foundational basis exists for Dr. Perez to express the opinions that
he did in this case. The facts and data upon which he based his opinion came from the plaintiff’s
deposition, his own interview with the plaintiff, his review of the documents and internal
correspondence that the defendant produced during discovery, various scientific articles in peer-
reviewed publications, and information published on the websites of various government agencies
and scientific organizations. These materials are similar to the kinds of information that expert
witnesses routinely rely upon in many cases of this nature. The fact that Dr. Perez obtained a first-
hand account of the plaintiff’s diesel exhaust exposures from reading the plaintiff’s deposition and
interviewing him does not affect the admissibility of his testimony. See id. Furthermore, Dr. Perez
testified that the plaintiff’s recounting of his exposures was corroborated by some of the
defendant’s internal communications and training presentation materials. Lacking specific
measurements of the plaintiff’s historical exposures, Dr. Perez explained why he believed the peer-
reviewed, published study by Dr. Pronk allowed him to accurately estimate the plaintiff’s historic
levels of exposure after interviewing the plaintiff. It was for Dr. Perez to determine the
informational basis necessary to express an opinion. Swartz, 264 Ill. App. 3d at 276.
¶ 58 We find that the defendant’s various criticisms of the factual basis for Dr. Perez’s testimony
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No. 1-21-1486
all go to the weight to be given to his testimony, not to its admissibility. This is true of his
knowledge concerning information about the locomotives used by the plaintiff in his job. See
Noakes, 363 Ill. App. 3d at 859 (medical experts’ unfamiliarity with various aspects of plaintiff’s
work affected only weight to be given to evidence and could be brought to light on cross-
examination). Also, we find that Dr. Perez adequately explained his reasons for why he did not
believe that the defendant’s internal diesel exhaust and pesticide studies were reliable. The
defendant will have the opportunity to bring out these purported shortcomings in his testimony
through cross-examination at trial.
¶ 59 Although the trial court did not reach the question of whether the methodology used by Dr.
Perez to reach his opinions satisfied the Frye test, we find it clear that he employed a methodology
that is generally accepted within the field of industrial hygiene for estimating the plaintiff’s
historical exposures to toxic substances. As set forth in greater detail above, Dr. Perez described a
methodology that he referred to as historical exposure assessment, which he testified was well-
established in the scientific literature of the field of industrial hygiene and had been used for
decades to estimate past exposures in situations where objective data did not exist. That
methodology involved his review of peer-reviewed literature and other data that had studied
occupational exposure to various contaminants in railroad environments. He then interviewed the
plaintiff to ascertain his job history, work environment, proximity to sources of contaminants, and
the nature of the contaminant sources he had experienced over the course of his career. Then, using
his training and expertise in industrial hygiene, Dr. Perez was able to combine this information to
gain an understanding of where the plaintiff fell within the context of the framework described in
the scientific literature, specifically the study by Pronk.
¶ 60 First, nothing about this process strikes us as particularly new or novel and thus subject to a
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No. 1-21-1486
Frye analysis. Donaldson, 199 Ill. 2d at 79 (“[o]nly novelty requires that the trial court conduct a
Frye evidentiary hearing”). Even if it was, however, we have reviewed the scientific articles that
Dr. Perez cited in support of the general acceptance of this methodology, and we find this
methodology well-described. These articles generally describe industrial hygienists performing
interviews with subjects to review job history information to assess whether an individual has had
exposure to the contaminant of interest and rating the exposure on a scaling system based on a
comparison with scientific literature studying the exposures of interest. 2 Thus, we conclude that
this methodology has found general acceptance among at least “some reasonable subset” of
scientists within the field. See Sandry,
367 Ill. App. 3d at 965. Furthermore, we take judicial notice
that, although employing the more stringent federal standard of Federal Rule of Evidence 702 and
Daubert v. Merrell Dow Pharmaceuticals, Inc.,
509 U.S. 579 (1993), at least six other judicial
decisions have approved of Dr. Perez’s use of the historical exposure assessment methodology as
a basis for expressing opinions in cases similar to this one. See Lemberger v. Union Pacific R.R.
Co.,
463 F. Supp. 3d 954, 967-68 (D. Neb. 2020); Ranney v. Union Pacific R.R. Co., No. 8:18-
CV-59,
2020 WL 3036200, at *8 (D. Neb. Jun. 5, 2020); Bettisworth v. BNSF Ry. Co., No. 8:17-
CV-491,
2020 WL 3498139, at *4-6 (D. Neb. Jun. 29, 2020); Jorn v. Union Pacific R.R. Co., No.
8:18-CV-138,
2020 WL 6261693, at *8 (D. Neb. Oct. 22, 2020); Cleaver v. Union Pacific R.R.
2
Hawkins, supra, at 61 (“Each industrial hygienist participated in a three-hour personal interview
… [during which the] expert reviewed chemical process information and then subjectively assessed the
distribution of exposures and the average exposure among the workers. … Industrial hygienists estimated
the average exposure and the 90th percentile of the exposure distribution with remarkable accuracy.”); V.
McGuire et al., Assessment of Occupational Exposures in Community-Based Case-Control Studies, 19
Ann. Rev. of Pub. Health 35, 40-41 (1998) (“The use of an industrial hygienist … is considered the most
accurate method for assessing chemical exposures in population-based case-control studies. Generally, one
or more industrial hygienists review job history information obtained from an in-person interview to assess
whether an individual has had exposure to each chemical agent of interest. The expert or experts rate the
exposure on a scaling system. … Continually updated bibliographic literature that is specific to putative
exposures of interest is needed.”).
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No. 1-21-1486
Co., No. 8:18-CV-512, 2021 WL 75259, at *6 (D. Neb. Jan. 7, 2021); Edgett v. Union Pacific R.R.
Co., No. 8:18-CV-407, 2021 WL 1238498, at *10 (D. Neb. Apr. 1, 2021).
¶ 61 Accordingly, we hold that the historical assessment exposure methodology employed by Dr.
Perez in this case satisfies the Frye test of general acceptance within the field of industrial hygiene.
As such, the trial court erred in barring him from expressing opinions and testimony at trial.
¶ 62 C. Dr. Chiodo
¶ 63 With respect to Dr. Chiodo, the trial court barred his testimony, based on its conclusion that
he had relied on two published articles for his opinion that diesel exhaust and herbicides cause B-
cell non-Hodgkin’s lymphoma and neither of those articles supported his conclusion. The trial
court found instead that these studies merely “claim there may be evidence of a positive
‘association with’ B-Cell Lymphoma.” The trial court stated that Dr. Chiodo had advanced no
scientific authority that “association” essentially means “causation” if no confounder is identified.
The trial court also found that Dr. Chiodo had relied upon the extrapolation principle, and it then
stated that neither the plaintiff nor Dr. Chiodo had provided scientific evidence that the method
Dr. Chiodo employed to reach his conclusions were generally accepted in the field of medical
causation.
¶ 64 On appeal, the plaintiff argues that the trial court erred in this analysis. First, the plaintiff
contends that Dr. Chiodo’s testimony does not implicate Frye because he did not use any new or
novel methodology to conclude that the plaintiff’s exposure to diesel exhaust and herbicide was a
likely cause of his non-Hodgkin’s lymphoma. He argues that Dr. Chiodo explained that his opinion
was based upon his knowledge, training, and experience that exposure to these carcinogens causes
lymphoma and that he used two studies recognizing an association between diesel exhaust and
herbicide exposure and lymphoma to corroborate his opinion. The plaintiff further asserts that Dr.
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No. 1-21-1486
Chiodo adequately explained that his method for doing so is generally accepted and that it is also
generally accepted that exposure to diesel exhaust causes non-Hodgkin’s lymphoma at a
probability level of 95% or greater.
¶ 65 For its part, the defendant argues that Dr. Chiodo’s deposition testimony displayed the
absence of a generally accepted methodology. It asserts that Dr. Chiodo denied any knowledge of
the plaintiff’s exposure to diesel exhaust and herbicides, that he had little to no experience
diagnosing or treating B-cell non-Hodgkin’s lymphoma, and that he had never published studies
or performed his own research pertaining to the disease. The defendant asserts that Dr. Chiodo was
unaware of information in the scientific literature concerning the dose necessary for herbicides or
diesel exhaust fumes to cause an individual to develop B-cell lymphoma. The defendant further
asserts that Dr. Chiodo knew almost nothing about the plaintiff’s associated risk factors, including
whether he was obese, whether he had a previous diagnosis of cancer, or what amount of time he
spent in specific roles during his railroad employment. The defendant states that, despite this lack
of knowledge, he simply testified that no threshold level exists below which diesel exhaust or
herbicide exposure cannot cause lymphoma.
¶ 66 The defendant characterizes Dr. Chiodo’s methodology as having “created an opinion to
support plaintiff’s theory” and then seeking out a single study “not to gather the available scientific
data, but only to corroborate his guesswork.” According to the defendant, Dr. Chiodo admitted
that he ignored or did not look for studies negative to his opinion. The defendant contends that Dr.
Chiodo’s reliance upon his knowledge, training, and experience in reaching his opinions is
undermined by the fact that he had no experience as a physician treating patients with B-cell
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No. 1-21-1486
lymphoma or with publishing about the disease or exposures. 3
¶ 67 The defendant states that the 2008 Karunanayake study cited by Dr. Chiodo does not
recognize that a causal connection exists between diesel exhaust experienced by railroad workers
and B-cell lymphoma. Rather, it recognizes only that an “association” exists. The defendant further
states that the study’s authors noted a potential flaw in that the participants in the study had a prior
personal history of cancer three times that of the control group.
¶ 68 Regarding the 2014 Schinasi article cited by Dr. Chiodo, the defendant asserts that Dr.
Chiodo “refused to confront whether the herbicide to which plaintiff was exposed even was
addressed.” The defendant states that, when Dr. Chiodo was confronted with data that glyphosate
(the herbicide identified as the one the plaintiff was exposed to) had not been listed by the
International Agency for Research on Cancer as a human carcinogen, Dr. Chiodo did not disagree.
¶ 69 After carefully considering the parties’ arguments, we agree with the plaintiff that the medical
causation testimony expressed by Dr. Chiodo in this case is not the type of scientific testimony
subject to a Frye analysis. In general, testimony by a physician about whether a particular event or
thing caused an injury is rarely subject to exclusion through the Frye test. See, e.g., Noakes, 363
Ill. App. 3d at 856-58 (“Medical testimony is not novel.”); Wartalski v. JSB Construction &
Consulting Co., 384 Ill. App. 3d 139, 146 (2008); Northern Trust Co.,
403 Ill. App. 3d at 276-77;
Mitchell, 317 Ill. App. 3d at 762; but see Agnew v. Shaw, 355 Ill. App. 3d 981, 990 (2005) (finding
no abuse of discretion in trial court’s ruling that methodology of “backward extrapolation” was
not generally accepted); Kane v. Motorola, Inc., 335 Ill. App. 3d 214, 222 (2002) (finding trial
3
Both the plaintiff and defendant assert that Dr. Chiodo also used the methodology of extrapolation
to reach his opinions in this case. However, we disagree. He testified multiples times during his deposition
that he “could” have used this methodology. He explained, however, that he did not need to extrapolate
because he had two articles clearly corroborating what he knew from his experience and training.
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No. 1-21-1486
court did not abuse its discretion in barring experts who were “unable to explain what steps they
took or methodologies they used to extrapolate their opinions” that radio frequency emitted by
antenna caused plaintiff’s brain tumor); Durbin v. Illinois Workers’ Compensation Comm’n, 2016
IL App (4th) 150088WC, ¶ 39 (employing Frye analysis to uphold workers’ compensation
arbitrator’s barring of causation opinion based on scientific articles).
¶ 70 Initially, we have difficulty determining exactly what the defendant contends is new or novel
with respect to Dr. Chiodo’s testimony that implicates Frye. The defendant does not squarely
address the plaintiff’s argument on this point in its brief. The only thing it refers to as “novel” is
Dr. Chiodo’s statement that “associated with” means “causes” in the absence of a confounder. The
defendant describes Dr. Chiodo’s methodology for reaching his opinions in a way that could be
characterized as perhaps “unreliable” but not new or novel. For example, the defendant states that
Dr. Chiodo’s methodology was to reach his opinion first and then seek out a single study that
would corroborate his research, without also looking for negative studies. However, there is
nothing new or novel about an expert first having an opinion based on training, education, and
experience and thereafter conducting a literature search for articles corroborating that opinion.
Criticisms that an expert’s literature search was not thorough does not make such a methodology
new or novel. Similarly, most of the rest of the defendant’s criticisms go to specific facts that Dr.
Chiodo allegedly failed to take into account, studies or publications that he has not undertaken,
and disagreement with the conclusions of the articles that he cited. However, these kinds of
criticisms do not make his methodology new or novel.
¶ 71 Instead of Dr. Chiodo’s methodology, it seems that what the defendant is suggesting is new
or novel is the existence of a causal link between diesel exhaust or herbicide exposure and non-
Hodgkin’s lymphoma. Again, however, as judges without medical training, we have difficulty with
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No. 1-21-1486
how to credit such an assertion. According to Dr. Chiodo, who is the only scientific expert to weigh
in on the matter in this case, these are well known causal links, not new or novel ones. He cites
two peer-reviewed articles which, according to him, support this conclusion at a 95% probability.
The defendant has not countered these assertions with any affidavit from an expert witness of its
own, nor has it cited the deposition testimony of any other expert demonstrating that this causal
link is new or novel. Likewise, the defendant has also not cited any peer-reviewed articles stating
that this causal link has been shown not to exist. All we have is argument by the defendant’s
attorneys on this point. Our supreme court has observed that the primary focus of a Frye test is
“ ‘counting scientists’ votes.’ ” (Internal quotation marks omitted.) Simons, 213 Ill. 2d at 532
(quoting People v. Miller, 173 Ill. 2d 167, 205 (1996) (McMorrow, J., concurring)). And
essentially the defendant here has not shown us any scientists’ votes that we can count in its favor
on this matter.
¶ 72 Furthermore, absent some other evidence, we do not believe that the causation opinions
expressed by Dr. Chiodo are made subject to Frye merely by the fact that the two articles cited by
him do not definitively state that diesel exhaust or herbicides cause non-Hodgkin’s lymphoma.
These articles clearly state that there is an increased risk or “association” between exposure to
these contaminants and non-Hodgkin’s lymphoma. According to Dr. Chiodo’s interpretation, they
state these conclusions at a level of 95% probability that the results did not occur by random
chance. The appellate court has previously rejected arguments to exclude causation testimony
under Frye based on scientific articles recognizing only an “association” or “increased risk”
between a thing and an injury without using the word “cause.” Northern Trust Co., 403 Ill. App.
3d at 277. Also, neither the Frye test nor Illinois law in general requires definitive medical or
scientific agreement on the existence of a causal relationship before a jury may hear evidence on
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No. 1-21-1486
the issue. Donaldson, 199 Ill. 2d at 78 (“ ‘[a] cause-effect relationship need not be clearly
established by animal or epidemiological studies before a doctor can testify that, in his opinion,
such a relationship exists’ ” (quoting Ferebee v. Chevron Chemical Co., 736 F.2d 1529, 1535-36
(D.C. Cir. 1984))); id. at 91 (“Illinois law does not require unequivocal or unqualified evidence of
causation”). The proper way to address the inconclusiveness of these studies is through cross-
examination and the presentation of contrary evidence. However, the statements within the studies
go to the weight to be given to Dr. Chiodo’s opinions, not to the admissibility of his testimony.
Swartz, 264 Ill. App. 3d at 277.
¶ 73 We also do not find Dr. Chiodo’s causation opinions to implicate the policy concerns of Frye.
The Frye test is primarily concerned with evaluating evidence produced through scientific tests or
studies that a jury may improperly regard with a sense of “infallibility” (Donaldson, 199 Ill. 2d at
86) or accord an undue significance due to its equating of science with truth. McKown,
226 Ill. 2d
at 254. Such concerns are not present with the causation testimony expressed by Dr. Chiodo.
Disputes regarding medical causation issues are common, and juries routinely hear and evaluate
disputed medical causation evidence in cases like this one. Experience informs us that juries do
not view as infallible or equate with truth an expert’s statement that he knows the cause of the
plaintiff’s injury from his experience as a physician or the fact that a medical journal article can
be cited to corroborate his opinion. This is especially true in cases such as this, where the scientific
literature cited is not unequivocal in its findings of causation and acknowledges the flaws in its
study, facts which must either be fronted on direct examination or exposed by opposing counsel
through cross-examination.
¶ 74 Finally, we find perhaps the most persuasive support for our conclusion in the following
observation quoted by our supreme court in Donaldson:
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No. 1-21-1486
“ ‘Judges, both trial and appellate, have no special competence to resolve the complex and
refractory causal issues raised by the attempt to link low-level exposure to toxic chemicals
with human disease. On questions such as these, which stand at the frontier of current
medical epidemiological inquiry, if experts are willing to testify that such a link exists, it
is for the jury to decide whether to credit such testimony.’ ” Donaldson, 199 Ill. 2d at 81
(quoting Ferebee, 736 F.2d at 1534).
We believe that this principle applies with respect to Dr. Chiodo’s testimony in this case. The
proper way for the defendant to address the weaknesses it perceives in his testimony is through
vigorous cross-examination and the presentation of contrary medical evidence through its own
witnesses at trial. The trial court erred in barring Dr. Chiodo from expressing opinions and
testimony at trial. 4
¶ 75 D. Summary Judgment
¶ 76 The defendant’s motion for summary judgment was predicated entirely upon its argument
that the opinions of Dr. Perez and Dr. Chiodo were inadmissible in their entirety and that, therefore,
the plaintiff could not establish the elements of his claim under the FELA. The trial court’s order
granting summary judgment in favor of the defendant was similarly predicated on this conclusion.
As we have reversed the trial court’s order barring those witnesses, we must likewise reverse the
entry of summary judgment in favor of the defendant. We conclude that, with the admissible
testimony and opinions of Dr. Perez and Dr. Chiodo, a genuine issue of material fact exists with
4
We point out that we are only addressing the issue of whether the opinions and testimony of Dr.
Perez and Dr. Chiodo should have been barred in their entirety for failure to satisfy the Frye test. We express
no opinion about whether any part of the testimony of either witness could later be stricken for any different
reason. See Northern Trust Co., 403 Ill. App. 3d at 278 (“a Frye determination is a threshold matter and
… opinion evidence surviving a Frye challenge may nevertheless be excluded if it lacks an evidentiary
foundation”).
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No. 1-21-1486
respect to all essential elements of the plaintiff’s claim under the FELA. See Bahus v. Union
Pacific R.R. Co., 2019 IL App (1st) 180722, ¶ 31 (to survive a motion for summary judgment in
an action under the FELA, the plaintiff must offer evidence that could prove the common law
elements of negligence, including duty, breach, foreseeability, and causation).
¶ 77 III. CONCLUSION
¶ 78 For the reasons set forth above, the trial court’s order barring Dr. Perez and Dr. Chiodo from
giving opinions or testimony at trial and granting summary judgment in favor of the defendant is
reversed, and this cause is remanded for further proceedings.
¶ 79 Reversed and remanded.
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No. 1-21-1486
Molitor v. BNSF Railway Co., 2022 IL App (1st) 211486
Decision Under Review: Appeal from the Circuit Court of Cook County, No. 18-L-1934;
the Hon. Mary Colleen Roberts, Judge, presiding.
Attorneys Stephen F. Monroe, of Marc J. Bern & Partners, LLP, of Chicago,
for and Jonathan Sternberg, of Jonathan Sternberg, Attorney, P.C., of
Appellant: Kansas City, Missouri, for appellant.
Attorneys Richard T. Sikes Jr. and Matthew C. Jardine, of Knight Nicastro
for MacKay, LLC, and Karen Kies DeGrand, of Donohue Brown
Appellee: Mathewson & Smyth LLC, both of Chicago, and S. Camille
Reifers, of Reifers, Holmes & Peters, LLC, of Memphis,
Tennessee, for appellee.
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