No. 33284 Clinton San Francisco and Jessie San Francisco, his wife v. Wendy's
International
Benjamin, J., dissenting:
I respectfully disagree with my colleagues that the circuit court should have
admitted into evidence the testimonies of Dr. Peter Gregor and Ewen Todd, Ph.D, putative
expert witnesses engaged by the appellants. I dissent specifically with respect to the
majority's adoption of syllabus points 4 and 5. I believe the majority's adoption of syllabus
point 4 will serve to have a lasting negative impact on litigation in the State of West Virginia
and our legal community, ultimately making summary judgment nothing more than an
unattainable fiction. Additionally, the majority, for reasons I cannot discern, has taken this
opportunity to adopt a rule of law (which has absolutely no application to the case before us
(See footnote 1) )
that will deprive our trial courts of their discretion to act on motions by requiring a hearing
prior to making a ruling on expert admissibility. Also troubling is the majority's reliance for
these changes on a minority view of law that has only been adopted by the First and Third
Circuits.
(See footnote 2)
I am most concerned that the majority believes that the summary judgment
process does not conform well to the discipline and analysis that
Daubert v. Merrell Dow
Pharmaceuticals, Inc., 509 U.S. 579, 113 S.Ct. 2786 (1993) and
Wilt v. Buracker, 191
W. Va. 39, 443 S.E.2d 196 (1993) impose. I do not believe that either holding was ever
intended to be rarely used at the summary judgment stage.
With respect to the specific testimony at issue, the focus of my disagreement
is not upon the qualifications of Dr. Gregor and Dr. Todd as experts in their specific fields
but upon the unreliability of both of their testimonies. The offered testimony of Dr. Gregor
should, in my opinion, be excluded because it is unreliable both in Dr. Gregor's diagnosis
of Mr. San Francisco's symptoms as a foodborne illness, specifically an
E. Coli 0157: H 7
bacteria-induced infection, and in his determination that the external cause of the illness was
a Wendy's hamburger that Mr. San Francisco had partially eaten within an hour or two prior
to the onset of his symptoms. (According to Dr. Todd, Mr. San Francisco became ill too
quickly for a typical
E. Coli infection to have occurred in that
E. Coli requires incubation of
three to seven days from ingestion for the pathogen to attach to the intestine walls and
produce verotoxin, the direct cause of an illness attributable to
E. Coli.) The offered
testimony of Dr. Todd should, in my opinion, be excluded because it is also unreliable, in this
case, by reason of Dr. Todd's theorizing
(See footnote 3) that the reason Mr. San Francisco's symptoms
occurred within a couple of hours after he had partially eaten the hamburger, instead of the
usual incubation period of three to seven days from ingestion, was because verotoxin had
already formed on the hamburger (pre-formed verotoxin) before it was eaten due to the
possibility that the beef had been abused, of which he had no direct evidence.
(See footnote 4)
I.
Daubert, Kumho Tire and Wilt
In
Daubert, the U.S. Supreme Court held that the traditional general
acceptance test enunciated in
Frye v. United States, 54 App. D.C. 46, 47, 293 F. 1013, 1014
(1923), which required that a scientific technique be generally accepted as reliable in the
scientific community in order to be admissible, was superseded by the adoption of the federal
rules of evidence. 509 U.S. 579, 113 S.Ct. 2786. The Court, in stating that the rules provide
the standard for admitting expert testimony, analyzed Rule 702 and found that nothing in the
rule stated that general acceptance was a prerequisite to admissibility. Subsequently, in
Wilt, 191 W. Va. 39, 443 S.E.2d 196, this Court concluded that
Daubert's analysis of Federal
Rule 702 should be followed in analyzing the admissibility of expert testimony under Rule
702 of the West Virginia Rules of Evidence. Neither decision explicitly, or implicitly,
cautions against utilizing summary judgment in the expert admissibility context. To the
contrary, the
Daubert Court specifically cautioned that
the Rules themselves place no limits on the admissibility of purportedly
scientific evidence. Nor is the trial judge disabled from screening such
evidence. To the contrary, under the Rules the trial judge must ensure
that any and all scientific testimony or evidence admitted is not only
relevant, but reliable.
Daubert, 509 U.S. at 588, 113 S.Ct. at 2795.
It is well recognized that because [t]he law must seek decisions that fall within
the boundaries of scientifically sound knowledge, Honorable Stephen Bryer,
Introduction
to Reference Manual on Scientific Evidence 4
(2d ed. 2000),
Daubert imposed a gatekeeping
function for trial courts to ensure that
only relevant and reliable scientific evidence reaches
the jury. (emphasis added). Rule of Evidence 702 imposes a special obligation upon a trial
judge to 'ensure that any and all scientific testimony. . .
is not only relevant, but reliable.'
Kumho Tire Co., Ltd. v. Carmichael, 526 U.S. 137, 147, 119 S.Ct. 1167, 1177
(1999)(quoting
Daubert, 509 U.S. at 589) (emphasis added). The very purpose of
Daubert,
is to make certain that an expert, whether basing testimony upon professional studies or
personal experience, employs in the courtroom
the same level of intellectual rigor that
characterizes the practice of an expert in the relevant field.
Kumho, 526 U.S. at 152
(emphasis added). The trial judge must have
considerable leeway in deciding in a particular
case how to go about determining whether particular expert testimony is reliable.
Id., 526
U.S. at 151 (emphasis added).
It is crucial that the factor of reliability continue to be determined by the circuit
court, in its gatekeeper capacity; not the jury, under the rubric of weight. Because reliability
is properly an issue of admissibility,
not weight, this is not an issue within the province of the
jury to conclude. I fear that holdings such as the majority's opinion herein will give the
illusion that reliability is, in essence, virtually an issue of weight. We must be reminded that,
In analyzing the admissibility of expert testimony under Rule 702 of the
West Virginia Rules of Evidence, the
trial court's initial inquiry must
consider whether the testimony is based on an assertion or inference
derived from the scientific methodology. Moreover, the testimony must
be relevant to a fact in issue. Further assessment should then be made
in regard to the expert testimony's reliability by considering its
underlying scientific methodology and reasoning. This includes an
assessment of (a) whether the scientific theory and its conclusion can
be and have been tested; (b) whether the scientific theory has been
subjected to peer review and publication; (c) whether the scientific
theory's actual or potential rate of error is known; and (d) whether the
scientific theory is generally accepted within the scientific community.
Syl. Pt. 2,
Wilt v. Buracker, 191 W. Va. 39, 443 S.E.2d 196 (emphasis added). Undoubtedly,
when an expert opinion is based on data, a methodology, or studies that are simply
inadequate to support the conclusions reached,
Daubert and Rule 702
mandate the exclusion
of that unreliable opinion testimony.
Amorgianos v. Nat'l R.R. Passenger Corp., 303 F.3d
256, 266 (2d Cir. 2002) (emphasis added).
II.
The Testimony of Dr. Peter Gregor
In the case before us, the majority holds that Dr. Gregor was both qualified to
render an expert opinion regarding causation and that his opinion was reliable because it was
formed through a scientific method called differential diagnosis. The majority, in adopting
Syllabus Point 5, concludes that a medical opinion based upon a properly performed
differential diagnosis is sufficiently valid to satisfy the reliability prong of Rule 702. I do not
agree with the majority's holding, particularly because the majority confuses the terms,
differential diagnosis and differential etiology. I believe Dr. Gregor simply was not
qualified to render an expert opinion on the
cause of the gastroenteritis from which Mr. San
Francisco was suffering, and any opinions in this regard were unequivocally unreliable.
While Dr. Gregor, a cardiologist, may have been qualified to testify as to the
indications, diagnosis, and treatment of food poisoning since he evaluated Mr. San Francisco
in the emergency room, I believe that he required more specialized knowledge and
information in order to testify regarding the issue of external causation. Dr. Gregor admitted
that, as a cardiologist, he was not an expert on etiology in foodborne illness. Despite this,
the majority relies upon
Westberry v. Gislaved Gummi AB, 178 F.3d 257, 262 (4
th Cir. 1999),
a case recognizing that a differential diagnosis, or differential etiology, is a standard
scientific technique of identifying the cause of the medical problem by eliminating the likely
causes until the most probable one is isolated sufficient to meet the requirement of Rule 702.
I agree with the contention set forth by the appellees, that the terms differential diagnosis and
differential etiology are two separate concepts - a differential diagnosis being a medical
process and differential etiology being a legal concept.
A. Differential Diagnosis
The majority defines the term differential diagnosis as a methodology
employed by medical practitioners to determine by a process of elimination both the disease
or condition from which a patient is suffering and the internal or external cause of the disease
or condition. The majority, like many courts, have used the term in a way that differs from
its dictionary definition and from its usage in the medical community.
(See footnote 5)
As recognized by the Eleventh Circuit Court of Appeals in
McClain v.
Metabolife Intern., Inc., 401 F.3d 1233, 1252 (11
th Cir. 2005):
Differential diagnosis involves the determination of which one
of two or more diseases or conditions a patient is suffering from,
by systematically comparing and contrasting their clinical
findings. DORLAND'S ILLUSTRATED MEDICAL
DICTIONARY 240, (Douglas Anderson et al. ed., 29th ed.
2000)). This leads to the diagnosis of the patient's condition,
not necessarily the cause of that condition. The more precise but
rarely used term [for determining the cause of a condition] is
differential etiology, which is a term used on occasion by
expert witnesses or courts to describe the investigation and
reasoning that leads to the determination of external causation,
sometimes more specifically described by the witness or court
as a process of identifying external causes by a process of
elimination. See Mary Sue Henifin et al., Reference Guide on
Medical Testimony, in REFERENCE MANUAL ON
SCIENTIFIC EVIDENCE 439, 481 (Fed. Jud. Ctr. 2d ed. 2000)).
At one level, the confusion is terminology in only semantic . . . .[h]owever, at another level
the confusion can mislead. 2 Faigman, Modern Scientific Evidence at §20-1.1 at 541. The
danger is that, in conflating these two concepts, a physician could, as here, be permitted to
testify beyond his or her areas of expertise. (See footnote 6)
While the two methodologies may employ a similar process, that of deduction
or elimination, the differences are more than nomenclature, they are substantive for [v]ery
different skill sets are usually involved in these two determinations, (See footnote 7) that of
diagnosing a
patient's condition and that of identifying the external cause of the condition. As one author
has explained:
The distinction between differential diagnosis and differential
etiology may seem subtle, but it is actually quite profound.
Although doctors receive substantial training on formulating a
differential diagnosis, they receive very little training, if any, on
how to conduct a differential etiology. Furthermore, doctors
rarely perform differential etiology when treating patients. . . .
If an elderly patient were to tell a doctor that she had shortness
of breath, the doctor may use a differential diagnosis to
eliminate heart disease, anemia, lung fibrosis, and emphysema
as possible causes. [The doctor] may then conclude that the most
likely cause of the shortness of breath is chronic bronchitis, an
internal disease. The physician would rarely analyze external
factors such as workplace conditions in practice, but patients
often call in doctors to do so in litigation. Thus, if a court were
to mistake a differential etiology analysis for a differential
diagnosis analysis, the court could errantly overemphasize the
physicians's qualification to give competent and relevant
testimony . . . In contrast to a differential diagnosis, evaluating
external causation is a process in which most physicians are
inexperienced and uncomfortable.
Spechler, supra, note 6, at 743-746. (See footnote 8)
Differential diagnosis involves a rigorous exercise in ruling out possible
diagnoses and ruling in the most likely diagnosis. Differential etiology involves ruling out
other possible external causes for the diagnosed condition and ruling in the mostly likely
external cause. As one commentator has observed,
suppose that the expert purported to rest the opinion solely or
primarily on the timing_the fact that the plaintiff contacted the
illness shortly after exposure to the alleged causal factor.[ (See footnote 9) ] There is a grave doubt whether such an opinion would even be
admissible. The opponent would have two cogent arguments.
Under amended Federal Rule 702(3), the opponent would urge
that the expert has not followed accepted methodology in
conducting the analysis. The opponent would have an even
stronger argument that the opinion is inadmissible because it is
not based upon sufficient facts or data. Inferring causation
from the timing is an example of the classical logical fallacy,
post hoc, ergo propter hoc _ it is illogical to infer that event A
caused condition B because A preceded B. Even if the judge
generously admitted a differential etiology opinion with such a
skimpy basis, that opinion certainly would not be adequate to
support a finding of specific causation.
Imwinkelried, supra, note 6, at 416-17 (internal footnotes omitted). (See footnote 10)
B. The Unreliability of Dr. Gregor's Causation Testimony
In the case at hand, a reliable and properly conducted differential diagnosis of
Mr. San Francisco's symptoms required Dr. Gregor to rule in or out pre-existing
gastrointestinal problems, alcohol use, peptic ulcer disease, diverticulitis, and foodborne
illness. A reliable and properly conducted differential etiology to determine an external
cause of the diagnosed condition (foodborne illness) required Dr. Gregor to rule in or rule
out a ham, home-cooked chicken strips, homemade beef stew, pork chops, potato salads, a
Wendy's hamburger, and other items that Mr. San Francisco had eaten within the week
preceding the onset of his symptoms as the cause of his symptoms. The appellees in their
brief represent that Dr. Gregor in his deposition acknowledged that he was not aware of Mr.
San Francisco's having eaten these foods, except for the Wendy's hamburger. How is it
possible for a physician to rule out other possible foods as the cause of Mr. San Francisco's
symptoms if he was unaware of what other foods had been eaten by Mr. San Francisco within
the typical incubation period for
E. Coli to develop into a verotoxin? Moreover, how could
Dr. Gregor reliably conclude that the Wendy's hamburger was the cause of his diagnosis of
Mr. San Francisco's symptoms if he did not consider that no other patrons of that same
Wendy's restaurant had reported any illness from eating a Wendy's hamburger on the day
that Mr. San Francisco developed his symptoms, including Mr. San Francisco's wife who ate
a portion of her own allegedly underdone hamburger?
The appellants represent that Dr. Gregor's testimony as to the diagnosis and
causation of Mr. San Francisco's illness has a sufficient factual background based on Dr.
Gregor's observations and treatment of the patient and that his testimony will assist the
trier of fact. Observations and treatment as the basis for making a diagnosis and
identifying a cause of a diagnosed condition fall far short of demonstrating that Dr. Gregor
made a properly conducted and reliable differential diagnosis of Mr. San Francisco's
symptoms and made a properly conducted and reliable differential etiology of the cause of
Mr. San Francisco's symptoms.
The appellants further contend: that Dr. Gregor noted that Mr. San Francisco
vomited 1.8 liters while in the emergency room, which he considered very substantial; that
after considering the patient's history, Dr. Gregor was able to rule out other causes for the
illness by performing a differential diagnosis which included his findings of no pre-existing
gastrointestinal problems, no alcohol use, no peptic ulcer disease and no history of
diverticulitis; that after a thorough clinical examination, Dr. Gregor was able to reach a
diagnosis and opinion as to causation, based on his examination of the patient and his
symptoms, the patient's medical history, his recent travel history and his food intake
history
(See footnote 11) ; and that each of the items was specifically considered. In so doing Dr. Gregor
testified, [i]f you ask me, do I think a hamburger at a restaurant with diarrhea, vomiting and
fluid loss shortly thereafter was the cause of the hospitalization, I would say yes . . . It was
the hamburger.
The appellants' arguments are for the most part conclusory and do not show
the procedures followed by Dr. Gregor in making a differential diagnosis of Mr. San
Francisco's condition or in making a differential etiology of the cause of the condition. They
only represent that Dr. Gregor reached a diagnosis and opinion as to causation, based on his
examination of the patient and his symptoms, the patient's medical history, his recent travel
history and his food intake history. An examination of the patient's symptoms and
various histories does not amount to the formation of a reliable opinion as to diagnosis or the
cause of the diagnosis based upon a properly conducted differential diagnosis and differential
etiology. Moreover, Dr. Gregor in his testimony acknowledged that his identification of the
cause of Mr. San Francisco's symptoms as being the Wendy's hamburger was because of the
temporal relationship between the eating of the hamburger by Mr. San Francisco and his
onset of the symptoms. As Imwinkelried noted in his Baylor Law Review article [i]nferring
causation from the timing is an example of the classical logical fallacy,
post hoc, ergo
propter hoc_it is illogical to infer that event A caused condition B simply because A
preceded B. Imwinkelried,
supra note 6, at 417
The majority opinion concludes that a differential diagnosis is a tested
methodology, has been subject to peer review/publication, does not frequently lead to
incorrect results, and is generally accepted in the medical community. Majority slip opin.,
pp. 21-22,
quoting Turner v. Iowa Fire Equip. Co., 229 F.3d 1202, 1208 (8
th Cir. 2000). The
majority further concludes that a medical opinion based upon a properly conducted
differential diagnosis is sufficiently valid to satisfy the reliability prong of the Rule 702
inquiry under
Dauber/Wilt. Majority slip opin., p. 25. The majority opinion notably does
not disclose why it believes that Dr. Gregor properly conducted a differential diagnosis in
both diagnosing Mr. San Francisco's condition and determining the cause of his condition.
For all of the above reasons, I would exclude the testimony of Dr. Gregor on
the basis that it is unreliable. Because it is evident that a differential diagnosis is not relevant
to the issue of causation, summary judgment was appropriate in this case.
(See footnote 12)
III.
The Testimony of Ewen Todd, Ph.D.
The majority admitted the testimony of Dr. Todd because they believe that Dr.
Todd's opinion explained precisely how the conclusions were reached, and pointed to an
objective source to show that his conclusions were based on a scientific source to show his
conclusions were based on a scientific method used by at least a minority of scientists in the
field. Majority Slip Opin., p. 29. My disagreement with the majority is based upon my
opinion that Dr. Todd's testimony is unreliable and for that reason should be excluded. The
appellants aptly described Dr. Todd's testimony as being his verotoxin theory. Dr. Todd's
testimony is unreliable for a very simple reason: he theorized that the hamburger which Mr.
San Francisco had partially eaten was contaminated with E.Coli; theorized that verotoxin
from the E. Coli had already formed on the hamburger before it was consumed; and theorized
that the pre-formed verotoxin accounted for the rapid onset of Mr. Francisco's symptoms
after he had eaten the hamburger. Dr. Todd conceded, however, that verotoxin is not pre-
formed in the absence of abusive manufacturing, and that he had no evidence that the
Wendy's hamburger had been subjected to such conditions. He stated, We don't have
any_any evidence directly that the beef was abused, but it's still a
possibility that that
occurred.
(See footnote 13) (Emphasis added).
Dr. Todd had no evidence that the hamburger eaten by Mr. Francisco was
contaminated with
E. Coli and that verotoxin had pre-formed thereon before it was eaten.
He had only his theories and possibilities. It is rather obvious that Dr. Todd developed his
theory to meet the exigencies of this litigation;
i.e., to explain the short temporal relationship
between the eating of the hamburger and the start of the symptoms, and to thereby hopefully
avoid the classic illogic of inferring that the hamburger caused Mr. San Francisco' symptoms
simply because the eating of the hamburger preceded the symptoms:
post hoc, ergo propter
hoc. Dr. Todd's testimony is theory unsupported by facts. It is unreliable and summary
judgment was appropriate.
IV.
Principles and Methodologies: A Matter of Admissibility or A Matter of Weight
While the Supreme Court said in
Daubert, that the focus, of course, must be
solely on principles and methodology, not on the conclusions that they generate[,] 509 U.S.
at 595, it subsequently explained that this language did not create a strict dichotomy between
methods and conclusions because conclusions and methodology are not entirely distinct
from one another.
General Elec. Co. v. Joiner, 522 U.S. 136, 146, 118 S.Ct. 512, 139
L.Ed.2d 508 (1997). [N]othing in either
Daubert or the Federal Rules of Evidence requires
a district court to admit opinion evidence that is connected to existing data only by the
ipse
dixit of the expert.
A court may conclude that there is simply too great an analytical gap
between the data and the opinion proffered.
Id. (emphasis added). In other words, trial
courts may focus on the conclusions of the experts in determining whether the data actually
supports the conclusion. Dick Thornsburgh,
Junk-Science-the Lawyer's Ethical
Responsibilities, 25 Fordham Urb. L.J. 449, 459 (1998).
Since
Daubert . . . parties relying on expert evidence have had notice of the
exacting standards of reliability such evidence must meet.
Weisgram v. Marley Co., 528
U.S. 440, 455, 120 S.Ct. 1011, 145 L.Ed.2d 958 (2000) (emphasis added). The law of
evidence has long been viewed as the product of the jury system, i.e., the need to shelter
untrained citizens from the temptation to accept uncritically that which may be unreliable and
of doubtful credibility. 1 Franklin D. Cleckley,
Handbook on Evidence for West Virginia
Lawyers, 1-9 (2d ed. 2000). Thus, expert witnesses merit special attention because their
testimony can be powerful and simultaneously very 'misleading because of the difficulty in
evaluating it.' Douglas R. Richmond,
Regulating Expert Testimony, 62 Mo. L. Rev. 485,
487 (1997)(citations omitted). In short, maintaining standards on the admissibility of expert
testimony is particularly important considering the aura of authority experts often exude,
which can lead juries to give more weight to their testimony.
Elsayed Muktar v. California
State Univ., 299 F.3d 1053, 1063-64 (9
th Cir. 2002).
When this Court adopted the
Daubert standard in
Wilt, Justice Neeley, in his
concurrence, foresaw the problems accompanying increasingly loose expert standards:
Today, virtually any doctor armed with a medical degree is
qualified to testify. Sometimes he will be expected to assert that
his opinion has a reasonable basis, that it does not originate in
chicken entrails or phases of the moon, but this is not much of
a standard. He need not be a recognized authority or specialist.
He need not reconcile his opinions with public-health statistics
of epidemiology. He need not establish that his diagnostic
methods or logical leaps enjoy general acceptance among
other doctors. Quite the contrary: he may insist that he alone
among doctors understands the importance or origins of certain
symptoms. He may claim, in short, to be a new Galileo, a lonely,
misunderstood genius who can see wonders that others neither
discern or understand. The standards are almost equally loose
for other, nonmedical experts.
Wilt, 191 W. Va. at 58-56, 443 S.E.2d at 212-13 (quoting Peter Huber,
Galileo's Revenge:
Junk Science in the Courtroom, 16 (1991)).
The recent decisions of this Court regarding the admissibility of expert
opinions now beg the question once again - how far will the boundaries of expert
admissibility continue to be stretched?
See Walker v. Sharma, __W.Va.__, __S.E.2d.__ (No.
33284 Nov. 21, 2007)(Benjamin, J., dissenting)(finding that once a trial court has found an
expert qualified to testify, a determination of weight to be afforded to the expert's testimony
rests within the province of the fact finder). My fear is that the majority, in going too far
astray from our prior precedent and the intent of our rules of evidence, is headed down a path
where virtually every aspect of expert testimony, including the factor of reliability, is
evaluated simply as a matter of weight, and not admissibility. However, my hope is that our
circuit courts (much like the circuit court at issue here) will properly balance the liberal thrust
of our rules of evidence with the need to preserve their role as gatekeepers and apply the new
rules of law enunciated by the majority in a careful, commonsensical manner, continuing to
utilize necessary legal tools such as summary judgment as the circumstances warrant.
For all of these reasons, I dissent.
Footnote: 1
Spechler, PHYSICIANS AT THE GATES OF DAUBERT: A LOOK AT THE ADMISSIBILITY
OF DIFFERENTIAL DIAGNOSIS TESTIMONY TO SHOW EXTERNAL CAUSATION IN
TOXIC TORT LITIGATION, 26 Rev. Litig. 739,743 (Summer 2007). See also Imwinkelried,
THE ADMISSIBILITY AND LEGAL SUFFICIENCY OF TESTIMONY ABOUT
DIFFERENTIAL DIAGNOSIS (ETIOLOGY): OF UNDER_AND OVER_ESTIMATIONS, 56
Baylor L. Rev. 391,402-03 (Spring 2004) (If the key question is the cause of the illness rather than
the nature of the illness, the physician uses a related, but distinct technique, that is, differential
etiology. It is true that the expressions 'differential diagnosis' and 'differential etiology are
sometimes utilized interchangeably as if they are synonymous. However, strictly speaking,
differential diagnosis uses process-of-elimination reasoning to identify the patients's illness while
differential etiology adopts the same mode of reasoning to determine the cause of the illness.);
Faigman, Symposium: The Role of the Judge in the Twenty-First Century[,] JUDGES AS
'AMATEUR SCIENTISTS,' 86 B.U.L. Rev. 1207, 1221 (December 2006) (Properly understood,
differential diagnosis refers to the identification of the illness or behavioral condition that a person
is experiencing. Differential etiology refers to the cause or causes of that condition.); Ertmer,
JUST WHAT THE DOCTOR ORDERED: THE ADMISSIBILITY OF DIFFERENTIAL
DIAGNOSIS IN PHARMACEUTICAL PRODUCT LITIGATION, 56 Vand. L. Rev. 1227,1228,
n. 5 (May 2003) ('Differential diagnosis,' as I use the term in this Note, is more properly referred
to as 'differential etiology.' The term 'differential diagnosis' actually refers to the process by which
physicians diagnose a patients's condition, rather than the cause of that condition. See, e.g., Faigman
et al., Modern Scientific Evidence: The Law and Science of Expert Testimony § 20-1.1 (2d ed.
2002). 'Differential etiology.' on the other hand, refers to the process of causal assessment. See
id.) See also 27 Minn. Prac., Products Liability Law § 16.20. (Internal footnotes have been omitted
from the above quotations.)