Lead Opinion
In this appeal from the Circuit Court of Kanawha County, we are asked to examine an order precluding the plaintiffs below from presenting the testimony of two expert witnesses in a case of food poisoning. The circuit court then went on to grant summary judgment to the defendant, on the basis that the plaintiffs did not have sufficient evidence to support their claim. On appeal, the parties debate whether the two experts — a treating physician and a director of a university food safety program — were qualified to testify and whether their opinions were sufficiently reliable to be admissible under Daubert v. Merrell Dow Pharmaceuticals, Inc.,
After careful review of the record, and of the excellent briefs and arguments by the parties, we find that the circuit court erred in excluding the two experts. As set forth below, we reverse the circuit court’s summary
I.
Facts & Background
Around noon on May 1, 2002, appellants Clinton and Jessie San Francisco visited a restaurant in Charleston, West Virginia, owned by the appellee, Wendy’s International, Inc. (“Wendy’s”). At the restaurant’s drive-through window, Mr. San Francisco purchased, among other items, a “single”sized hamburger with mustard, onions, pickles and tomato. The appellants then drove off and began eating their meals in the car.
Mr. San Francisco had eaten approximately one-quarter of his hamburger when he noticed that the burger was “red inside and wasn’t done, it was raw,” “tasted funny” and that the texture was “soft.” After this observation, Mr. San Francisco discarded the remainder of the hamburger.
Shortly thereafter, Mr. San Francisco became ill. His stomach began to bother him and he began to sweat profusely. Within one-and-a-half to two hours after eating the hamburger, Mr. San Francisco began experiencing vomiting and diarrhea.
Two days later, after continued pain and discomfort, on May S, 2002, Mr. San Francisco was admitted to Logan General Hospital.
While at Logan General, Mr. San Francisco was treated by Dr. Peter Gregor, a physician who is board certified in internal medicine and cardiology and is familiar, based on his clinical experience, with a food poisoning diagnosis. Dr. Gregor conducted a work up and analysis of Mr. San Francisco and performed a “differential diagnosis” to determine the cause of his illness. Using this method of diagnosis, during his examination, Dr. Gregor considered and then ruled out other potential causes of Mr. San Francisco’s illness, such as pre-existing gastrointestinal problems, alcohol use, peptic ulcer disease or diverticulitis. After considering Mr. San Francisco’s history and condition — particularly noting that he vomited 1.8 liters of material while in the emergency room, an amount which Dr. Gregor considered substantial — Dr. Gregor concluded to a reasonable degree of medical certainty that Mr. San Francisco was suffering from a foodborne illness caused by the Wendy’s hamburger. As Dr. Gregor later stated in his deposition:
If 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.
On April 19, 2004, Mr. and Mrs. San Francisco filed the instant lawsuit against appellee Wendy’s, alleging that the appellee had caused injury to Mr. San Francisco by selling an “unsafe, unwholesome, or unfit food product.”
During discovery, the appellants identified two experts. The appellants identified Dr. Gregor as an expert who would testify that Mr. San Francisco suffered from a foodborne illness caused by the Wendy’s hamburger. The appellants also identified Ewen Todd, Ph.D., an expert in food safety and toxicology from Michigan State University. Dr. Todd testified in a deposition that although the symptoms of Mr. San Francisco’s illness were most consistent with verotoxin produced by E. coli 0157:H7 bacteria, he became ill too quickly for a typical E. coli infection to have occurred; E. coli bacteria apparently require incubation of three to seven days from ingestion to produce enough verotoxin to induce symptoms. Instead, Dr. Todd was of the opinion that E. coli bacteria was present on the ground beef in the Wendy’s hamburger; that the bacteria had produced vero-toxin; and that the ingestion of the verotoxin in the Wendy’s hamburger had produced the rapid onset of Mr. San Francisco’s symptoms. Dr. Todd’s opinion was based upon a published scientific study which found that four days after E. coli bacteria was added to ground beef, verotoxins formed in the beef.
In an order dated March 14, 2006, the circuit court excluded the testimony of Dr. Gregor and Dr. Todd, and granted summary judgment to the appellee. The circuit court concluded that under Rule 702, Dr. Gregor was not “qualified as an expert by knowledge, skill, experience, training or education.” Further, the circuit court found that Dr. Todd’s opinion was “unreliable as a matter of law and inadmissible” under Daubert and Wilt. In the absence of the testimony of the two experts, the circuit court found insufficient evidence that Mr. San Francisco suffered from a foodborne illness caused by the Wendy’s hamburger, and therefore granted summary judgment to the appellee.
The appellants now appeal the circuit court’s March 14, 2006 order.
II.
Stand,ard, of Review
Our review of a circuit court’s decision to grant a party a summary judgment under Rule 56 of the Rules of Civil Procedure is reviewed de novo. Syllabus Point 1, Painter v. Peavy,
When considering the propriety of a circuit court’s decision to admit or exclude the testimony of an expert witness, we generally examine the decision for an abuse of discretion. As we stated in Syllabus Point 6 of Helmick v. Potomac Edison Co.,
The admissibility of testimony by an expert witness is a matter within the sound discretion of the trial court, and the trial court’s decision will not be reversed unless it is clearly wrong.
See also Syllabus Point 5, Overton v. Fields,
However, when a circuit court excludes expert testimony as unreliable under the Daubert/Wilt gatekeeper analysis, we will review the circuit court’s method of conducting the analysis de novo. Syllabus Point 3, in part, Gentry v. Mangum, supra. (“Under Daubert ... and Wilt ... the reliability requirement is met only by a finding by the trial court under Rule 104(a) of the West Virginia Rules of Evidence that the scientific or technical theory which is the basis for the test results is indeed ‘scientific, technical, or specialized knowledge.’ The trial court’s determination regarding whether the scientific evidence is properly the subject of scientific, technical, or other specialized knowledge is a question of law that we review de novo ”). See also Norris v. Baxter Healthcare Corp.,
With these standards in mind, we turn to the parties’ arguments.
III.
Discussion
A.
General Principles under Rule 702
The appellants argue that the circuit court misinterpreted the West Virginia Rules of
“The Rules of Evidence embody a strong and undeniable preference for admitting any evidence which has the potential for assisting the trier of fact.” Kannankeril v. Terminix International, Inc.,
If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise.
“Rule 702 reflects an attempt to liberalize the rules governing the admissibility of expert testimony.” Weisgram v. Marley Co.,
Following in the footsteps of the U.S. Supreme Court’s decision in Daubert v. Merrell Dow Pharmaceuticals, Inc.,
As to the first part of the inquiry, in Syllabus Point 5 of Gentry the Court explained the steps that a trial court should take to determine if an expert is qualified to render an opinion under Rule 702:
In determining who is an expert, a circuit court should conduct a two-step inquiry. First, a circuit court must determine whether the proposed expert (a) meets the minimal educational or experiential qualifications (b) in a field that is relevant to the subject under investigation (c) which will assist the trier of fact. Second, a circuit court must determine that the expert’s area of expertise covers the particular opinion as to which the expert seeks to testify.
“Rule 702 permits a circuit court to qualify an expert by virtue of education or experience or by some combination of these attributes .... [W]e have stated clearly that a broad range of knowledge, skills, and training qualify an expert as such, and rejected any notion of imposing overly rigorous requirements of expertise.” Gentry,
Second, if the expert is qualified, the analysis turns to whether the expert’s proffered opinion is relevant and reliable. In Wilt, this Court adopted a standard similar to that established by the United States Supreme Court in Daubert. The Wilt Court stated, in Syllabus Point 2, 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 scientificmethodology. Moreover, the testimony must be relevant to a fact at 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.
We later expounded upon our holding in Wilt in Syllabus Point 4 of Gentry, where we explained:
When scientific evidence is proffered, a circuit court in its “gatekeeper” role under Daubert v. Merrell Dow Pharmaceuticals, Inc.,509 U.S. 579 ,113 S.Ct. 2786 ,125 L.Ed.2d 469 (1993), and Wilt v. Buracker,191 W.Va. 39 ,443 S.E.2d 196 (1993), cert denied,511 U.S. 1129 ,114 S.Ct. 2137 ,128 L.Ed.2d 867 (1994), must engage in a two-part analysis in regard to the expert testimony. First, the circuit court must determine whether the expert testimony reflects scientific knowledge, whether the findings are derived by scientific method, and whether the work product amounts to good science. Second, the circuit court must ensure that the scientific testimony is relevant to the task at hand.
As noted above, Daubert and Wilt provide several factors a trial court can apply to assess the reliability of expert testimony: whether the scientific theoiy and its conclusion can be or have been tested; whether the scientific theoiy has been subjected to peer review and publication; whether the scientific theory’s actual or potential rate of error is known; and whether the scientific theory is generally accepted within the scientific community. Syllabus Point 2, Wilt.
These factors are by no means a definitive checklist or test of reliability. Other courts have developed additional factors, such as whether the scientific theory “was developed for litigation or naturally flowed from the expert’s research; whether the proposed expert ruled out other alternative explanations; and whether the proposed expert sufficiently connected the proposed testimony with the facts of the case.” Lauzon v. Senco Products, Inc.,
When assessing the reliability of an expert’s opinion, a trial court’s role as a “gatekeeper” is to determine whether the reasoning or methodology underlying the testimony is scientifically valid. “Evaluating the reliability of scientific methodologies and data does not generally involve assessing the truthfulness of the expert witnesses!.]” Gentry,
conducts an inquiry into the validity of the underlying science, looldng at the soundness of the principles or theories and the reliability of the process or method as applied to the ease. The problem is not to decide whether the proffered evidence is right, but whether the science is valid enough to be reliable.
Gentry,
The instant case raises a problem, one that was alluded to by the Court in Gentry, and that is when and how challenges to the reliability of an expert’s testimony are brought under Rule 702 and Daubert/Wilt. Gentry,
In Gentry, the Court suggested that DaubeH/Wilt challenges to scientific evidence should be rare, and said that “most scientific validity issues will be resolved under judicial notice pursuant to Rule 201.” Id. However, when challenges need to be made, the Gentry Court indicated that motions in limine are likely the best vehicle, because “the best time to review and resolve scientific issues is at the pretrial level.”
DaubeH/Wilt challenges can play a role during the summary judgment phase of civil litigation. However, the few courts addressing the issue have concluded that the Dau-bert gatekeeping regime is of limited utility in the context of a summary judgment motion, and have held that the better practice is to permit the parties a hearing to defend the admissibility of an expert’s proffered opinion. As one court stated:
The fact that DaubeH can be used in connection with summary judgment motions does not mean that it should be used profligately. A trial setting normally will provide the best operating environment for the triage which DaubeH demands. Voir dire is an extremely helpful device in evaluating proffered expert testimony ... and this device is not readily available in the course of summary judgment proceedings. Moreover, given the complex factual inquiry required by Daubert, courts will be hard-pressed in all but the most clearcut cases to gauge the reliability of expert proof on a truncated record. Because the summary judgment process does not conform well to the discipline that DaubeH imposes, the DaubeH regime should be employed only with great care and circumspection at the summary judgment stage.
We conclude, therefore, that at the junction where Daubert intersects with summary judgment practice, Daubert is accessible, but courts must be cautious — except when defects are obvious on the face of a proffer — not to exclude debatable scientific evidence without affording the proponent of the evidence adequate opportunity to defend its admissibility.
Cortés-Irizarry v. Corporación Insular de Seguros,
We have long stressed the importance of in limine hearings under Rule 104(a) in making the reliability determination required under Rule 702 and DaubeH. SeeUnited States v. Downing, 753 F.2d 1224 , 1241 (3d Cir.1985) (“It would appear that the most efficient procedure that the district court can use in maldng the reliability determination is an in limine hearing.”). In In re Paoli Railroad Yard PCB Litigation,916 F.2d 829 (3d Cir.1990), we reversed a summary judgment for defendants because the district court, in excluding expert evidence under Rule 703, had failed to “provide [ ] the plaintiffs with sufficient process for defending their evidentiary submissions.” Id. at 854. We explained:
The adversarial process upon which our legal system is based assumes that a fact finder will give the parties an adequate opportunity to be heard; if it does not, it cannot find facts reliably. Thus, the detailed factual record requirement, firmly entrenched in our jurisprudence, requires adequate process at the eviden-tiary stage, particularly when a summary judgment may flow from it.
Id. (citations omitted). We reiterated our Paoli holding in Hines v. Consolidated Rail Corp.,926 F.2d 262 , 272 (3d Cir.1991) (“A detailed factual record is required at the evidentiary stage, particularly when a summary judgment may result.”). And in In re Paoli Railroad Yard PCB Litigation,35 F.3d 717 (3d Cir.1994), we declared:
Given the “liberal thrust” of the federal rules it is particularly important that the side trying to defend the admission of evidence be given an adequate chance to do so.
Id. at 739 (citation omitted); see also Margaret A. Berger, Procedural Paradigms for Applying the Daubert Test, 78 Minn. L.Rev. 1345, 1365 (1994) (reviewing admissibility of expert testimony in light of the “liberal thrust” of the Federal Rules of Evidence).
Although courts considering the question have found that in limine hearings are generally recommended prior to maldng a Dwnbert-type determination, they are not required. “The only legal requirement is that the parties ‘have an adequate opportunity to be heard’ before the district court makes its decision.” Group Health Plan, Inc. v. Philip Morris USA, Inc.,
Prior to any Daubeti determination or other decision regarding the proffer of expert evidence, the parties must be afforded the opportunity to be heard. We generally recommend that the trial court conduct an in limine hearing specifically on the subject, as this procedure will result in full briefing and argument by the par-ties regarding the proposed expert testimony. This will not only assist the trial court in its function as evidentiary gatekeeper; it will provide a fuller record for an appellate court should the parties contest the eviden-tiary ruling. While an in limine hearing may not be necessary in all cases, it does provide the most efficient manner of addressing the issue in many cases.
Smith ex rel. Smith v. Clement, — So.2d -, -,
We therefore hold that because the summary judgment process does not conform well to the discipline and analysis that Daubert and Wilt impose, the Daubert/Wilt regime should be employed only with great care and circumspection at the summary judgment stage. Courts must be cautious— except when defects are obvious on the face of a proffered expert opinion — not to exclude debatable scientific evidence without affording the proponent of the evidence adequate opportunity to defend its admissibility. Given the plain language of the West Virginia Rules of Evidence, the side trying to defend the admission of expert evidence must be given an adequate chance to do so.
With these guidelines in mind, we turn now to the specific arguments of the parties concerning the proffered expert opinions of Dr. Gregor and Dr. Todd.
The Testimony of Dr. Gregor
The appellants argue that the circuit court abused its discretion in excluding Dr. Gregor’s testimony, because (1) Dr. Gregor is qualified as an expert to render an opinion on the identity and cause of appellant Mr. San Francisco’s illness, and (2) Dr. Gregor’s opinion is reliable under Daubert/Wilt.
As to Dr. Gregor’s qualifications as an expert, the appellants assert that Dr. Gregor is a physician board-certified in internal medicine with a sub-specialty in cardiovascular disease. During his time in practice from 1979 until 2002 (some twenty-three years), Dr. Gregor treated numerous gastrointestinal conditions, including diagnosing and treating multiple patients suffering from foodborne illnesses. The appellants point out that the Gentry Court stated that “once an expert passes the minimal threshold, further credentials affect the weight of the testimony not its admissibility."
The appellee, however, argues that Dr. Gregor does not have a specialization in gas-troenterology or epidemiology. Further, Dr. Gregor had never testified in court regarding foodborne illnesses prior to this case, had never conducted research or studies on the topic, and had never worked in the fields of epidemiology or public health. The appellee cites to Dr. Gregor’s own deposition testimony, where he admitted that medical experts in other fields would be better qualified to render an opinion:
A. ... And I’m not an expert in the etiology of foodborne illness, nor do I claim to be one today.
Q. Okay. Would you then defer to the opinions of a qualified gastroenterologist or infectious disease expert on those issues regarding etiology?
A. As regards to organism?
Q. Right. Organism or causation.
A. Yes.
The appellee argues that, while Dr. Gregor is highly qualified as a board certified cardiologist, he is not a gastroenterologist, infectious disease physician, public health physician, or epidemiologist — all of which are medical fields that deal specifically with foodborne illnesses. Accordingly, the appellee asserts that the circuit court was fairly persuaded that Dr. Gregor did not possess the necessary threshold of expertise to testify, and properly was within its discretion in excluding Dr. Gregor’s testimony.
After careful consideration, we reject the appellee’s position because it is directly contrary to Rule 702 and our holding in Gentry. Rule 702 states that a broad range of knowledge, skills, and training qualify an expert as such, and Gentry made clear that we have rejected any notion of imposing overly rigorous requirements of expertise. In Gentry, the Court expressed the concern that there is no “best expert” rule, and “[n]either a degree nor a title is essential, and a person with knowledge or' skill borne of practical experience may qualify as an expert.”
The Gentry Court stated plainly that [disputes as to the strength of an expert’s credentials ... go to weight and not to the admissibility of their testimony.
As a physician board-certified in internal medicine, with several decades of experience
Accordingly, we conclude that the circuit eoui't erred in excluding Dr. Gregor’s testimony on the basis that Dr. Gregor was not qualified to offer expert testimony under Rule 702.
Once an expert is deemed qualified, the trial court must address whether the methodology underlying the expert’s conclusion is reliable. The appellants argue that Dr. Gregor’s opinion is reliable under the DaubeH/Wilt analysis, and that the circuit court erred when it excluded the opinion.
The appellants assert that Dr. Gregor’s opinion was farmed through a scientific method called “differential diagnosis.” “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.’ ” McClain v. Metabolife Intern., Inc.,
The appellants indicate that Dr. Gregor was on staff at Logan General Hospital on May 3, 2002, and treated Mr. San Francisco in the hospital’s emergency room. Dr. Gre-gor noted his patient’s symptoms, particularly noting that Mr. San Francisco vomited 1.8 liters while in the emergency room. After considering his patient’s symptoms and history, Dr. Gregor ruled out various likely causes for the illness after finding no pre-existing gastrointestinal problems, no alcohol use, no peptic ulcer disease and no history of diverticulitis. Dr. Gregor conducted a clinical examination of Mr. San Francisco, reviewed his medical history, his recent travel history, and his food intake history. Taking all of these factors together, Dr. Gregor eliminated various likely causes and concluded that the most probable cause of Mr. San Francisco’s problem was a foodborne illness caused by the allegedly undercooked Wendy’s hamburger. Wfaen asked why he chose the undercooked hamburger as the cause of plaintiffs illness as opposed to other possibilities, Dr. Gregor explained “[i]t’s the highest probability of a series of possibilities.”
The appellee responds by arguing that Dr. Gregor’s opinion is still unreliable and inadmissible. While Dr. Gregor might be trained in the process of deducing a disease based on a set of symptoms and laboratory tests, the appellee argues that Dr. Gregor was essentially speculating about the cause of Mr. San Francisco’s illness. The appellee suggests in its brief, as a factual matter, that there are “more obvious culprits of Mr. San Francisco’s illness” in the foods that Mr. San Francisco ate
In general terms, physicians routinely rely upon differential diagnosis for establishing causation. The overwhelming majority of courts that have addressed the issue have held that a medical opinion on causation based upon a reliable differential diagnosis is sufficiently valid to satisfy the reliability prong of the Rule 702 inquiry. “Most circuits have held that a reliable differential diagnosis satisfies Daubert and provides a valid foundation for admitting an expert opinion. The circuits reason that a differential diagnosis is a tested methodology, has been subjected to peer review/publication, does not frequently lead to incorrect results, and is generally accepted in the medical community.” Turner v. Iowa Fire Equip. Co.,
Even with all the advances of medical science, the practice of medicine remains an art. A properly conducted and explained differential diagnosis is not “junk science.” If a differential diagnosis provides a sufficient basis on which to prescribe medical treatment with potential life-or-death consequences, it should be considered reliable enough to assist a fact finder in understanding certain evidence or determining certain fact issues.
Coastal Tankships, U.S.A., Inc. v. Anderson,
However, while most courts recognize the methodology of differential diagnosis as a scientifically valid way of determining causation, the same courts also warn that opinions based on differential diagnosis must be analyzed on a case-by-case basis, ensuring that the expert’s application of the technique is reliable and proper in each case. As the Eleventh Circuit Court of Appeals explained:
[A]n expert does not establish the reliability of his techniques or the validity of his conclusions simply by claiming that he performed a differential diagnosis on the patient. ... “No one doubts the utility of medical histories in general or the processby which doctors rule out some known causes of disease in order to finalize a diagnosis. But such general rules must ... be applied fact-specifically in each case.”
McClain v. Metabolife Int’l, Inc.,
Thus, an expert’s use of differential diagnosis is reliable and valid only if the expert applied the technique in a manner which is also reliable. “A reliable differential diagnosis typically, though not invariably, is performed after physical examinations, the taking of medical histories, and the review of clinical tests, including laboratory tests, and generally is accomplished by determining the possible causes for the patient’s symptoms and then eliminating each of these potential causes until reaching one that cannot be ruled out or determining which of those that cannot be excluded is the most likely.” Westberry,
The elements of a differential diagnosis may consist of the performance of physical examinations, the taking of medical histories, and the review of clinical tests, including laboratory tests. A doctor does not have to employ all of these techniques in order for the doctor’s diagnosis to be reliable. A differential diagnosis may be reliable with less than all the types of information set out above....
Depending on the medical condition at issue and on the clinical information already available, a physician may reach a reliable differential diagnosis without himself performing a physical examination, particularly if there are other examination results available. In fact, it is perfectly acceptable, in arriving at a diagnosis, for a physician to rely on examinations and tests performed by other medical practitioners.
Kannankeril v. Terminix Intern., Inc.,
Differential diagnosis is not a scientific method which lends itself to establishing a direct link between an activity and an illness or injury. Instead, it is a method by which a physician “considers all relevant potential causes and then eliminates alternative causes....” Federal Judicial Center, Reference Manual on Scientific Evidence 214 (1994). It is a process of elimination based upon a study limited to an evaluation of the patient alone.
We therefore conclude that a medical opinion based upon a properly performed differential diagnosis is sufficiently valid to satisfy the reliability prong of the Rule 702 inquiry under Daubert/Wilt. A differential diagnosis is a tested methodology, has been subjected to peer review/publication, does not frequently lead to incorrect results, and is generally accepted in the medical community. Opinions based on differential diagnosis must be analyzed on a case-by-case basis, ensuring that the medical expert’s application of the technique is reliable and proper in each case.
When Dr. Gregor was questioned regarding his opinion as to causation, and why he chose the undercooked hamburger as the cause of the appellant’s illness as opposed to other possibilities, Dr. Gregor explained that “[i]t’s the highest probability of a series of possibilities.” Appellee Wendy’s argues that Dr. Gregor’s differential diagnosis was unreliable
We therefore conclude that, under a Dau-bert/Wilt analysis, Dr. Gregor’s differential diagnosis of the cause of Mr. San Francisco’s illness is reliable and admissible.
C.
The Admissibility of Dr. Todd’s Testimony
The appellants next argue that the circuit court erred in excluding the testimony of their food safety expert, Dr. Todd, on the basis that his theory was unreliable. Dr. Todd indicated that Mr. San Francisco’s rapid illness was consistent with eating preformed verotoxin produced by E. coli 0157:H7 bacteria in the undercooked Wendy’s hamburger. The circuit court excluded Dr. Todd’s opinion based upon the appellee’s argument that there has, to date, been limited publication or peer review on this subject, and that none of the medical tests performed on Mr. San Francisco at Logan General Hospital — several days after eating the hamburger — found verotoxin or E. coli bacteria.
The appellants argue that Dr. Todd’s theory is logical and is supported by published literature. Based upon Mr. San Francisco’s symptoms, Dr. Todd concluded to a reasonable degree of probability that the cause of Mr. San Francisco’s illness was from preformed verotoxin produced by E. coli in ground beef. To support this, Dr. Todd cited to a study in a journal which found that E. coli sitting in uncooked ground beef can produce verotoxin. Furthermore, the appellants point to Dr. Todd’s wealth of knowledge on the subject of food safety; the record contains Dr. Todd’s cumculivm vitae, which extends for some 77 single-spaced pages.
The appellees respond that Dr. Todd’s conclusions are not reliable under a Daubert/Wilt analysis. The appellees concede that, in Daubert, Wilt and Gentry, trial judges were admonished that the focus of their reliability analysis must be “solely on principles and methodology, not on the conclusions they generate.” Daubert,
Still, the appellees contend that “nothing in the Rules [of Evidence] appears to have been intended to permit experts to speculate in fashions unsupported by ... the uncontroverted evidence.” Gentry,
The appellants counter the appellee’s position by arguing that, in proving a food poisoning lawsuit, positive proof by scientific testing is not required. Instead, the appellants argue that “[i]n the absence of direct evidence of the defectiveness of the food, recovery could be supported by circumstantial evidence if every other reasonable hypothesis as to the cause of the plaintiffs illness could be excluded.” Castleberry’s Food Co. v. Smith,
To begin, this Court has never required “positive proof by scientific testing to establish a factual basis for medical diagnosis and opinion.” Bussey v. E.S.C. Restaurants, Inc.,
The circuit court based its decision to exclude Dr. Todd’s testimony, in large part, upon the fact that his conclusion had not been tested, and that his theory had not been subjected to peer review and publication. Syllabus Point 2, Wilt. However, these factors listed in Wilt are by no means a definitive checklist or test of reliability.. Our review of the record indicates that Dr. Todd sufficiently connected the proposed testimony with the facts of the case. Because food poisoning is a fairly common illness, we see nothing novel in Dr. Todd’s theory that would warrant great interest in its publication. Further, a court may treat an expert’s qualifications as circumstantial evidence that he or she has used a scientifically valid methodology or mode of reasoning in drawing his or her conclusions. Ambrosini v. Labarraque,
We believe that the conflict between the positions taken by the parties regarding Dr. Todd’s conclusions did not render his testimony unreliable, but instead created a jury issue regarding the weight to be given to the testimony. Accordingly, we find that the circuit court erred in excluding Dr. Todd’s testimony.
D.
Order Granting Summary Judgment
Finally, the appellants contend that the circuit court erred in granting summary judgment to the appellees, after excluding both of the appellant’s causation witnesses.
“A motion for summary judgment should be granted only when it is clear that there is no genuine issue of fact to be tried and inquiry concerning the facts is not desirable to clarify the application of the law.” Syllabus Point 3, Aetna Casualty & Surety Co. v. Federal Insurance Co., of New York,
The cireuit court granted summary judgment on the basis that the appellants had no evidence of causation, that is, no evidence that the Wendy’s hamburger was the cause of Mr. San Francisco’s illness. Having found that the circuit court erred in excluding both of the appellants’ causation experts, we now find that the appellants made a sufficient showing on an essential element of the case that they had the burden to prove. Accordingly, because it now appears from the record that genuine issues of fact exist to be tried, we find that the circuit court erred in granting summary judgment.
IV.
Conclusion
The circuit court’s order of March 14, 2006 is reversed, and the case is remanded for further proceedings.
Reversed and Remanded.
Notes
. The appellants are residents of Logan, West Virginia.
. See Risini D. Weeratna and Michael P. Doyle, "Detection and Production of Verotoxin 1 of Escherichia coli 0157:H7 in Food,” 57 Applied and Environmental Microbiology 2951 (Oct. 1991).
. One court summarized the non-exclusive guidelines as including:
(1) whether a method consists of a testable hypothesis; (2) whether the method has been subject to peer review; (3) the known or potential rate of error; (4) the existence and maintenance of standards controlling the technique’s operation; (5) whether the method is generally accepted; (6) the relationship of the technique to methods which have been established to be reliable; (7) the qualifications of the expert witness testifying based on the methodology; and (8) the non judicial uses to which the method has been put.
In re Paoli R.R. Yard PCB Litigation,
. In the week before eating the hamburger, Mr. San Francisco ate a ham, home-cooked chicken strips, homemade beef stew, pork chops, potato salad, and other items. The appellee asserts that the time lapse between eating these foods and the onset of illness is an incubation period consistent with the general state of medical knowledge concerning the length of time it takes for tainted food to cause food poisoning.
. Mr. San Francisco visited his grandson in the hospital in the days before his illness. The ap-pellee posits that Mr. San Francisco may have contracted a bacteria or virus from another individual or from contact with a surface of some sort during this visit.
. See, e.g., Feliciano-Hill v. Principi,
. The record indicates that Dr. Todd secured a Ph.D. in the "Taxonomy of Staphylococci and Micrococci” in 1968 from the University of Glasgow, Scotland. He then emigrated to Canada, where he worked until 2001 as a research scientist on the “reporting and surveillance of food-borne disease" for the Health Protection Branch of Health Canada. Dr. Todd is currently the Director of the National Food Safety and Toxicology Center at Michigan State University.
. We note, however, that Dr. Todd said in his deposition that his opinion was based upon county health department inspection reports which, on five occasions, cited the Wendy's restaurant for "temperature abnormalities” such as "temperatures that were either above the recommended temperature for storage of food or below the temperature for dishwasher use.”
Concurrence Opinion
concurring:
(Filed November 26, 2007)
In the case mb judice, the trial court excluded the testimony of the appellants’ two expert witnesses because it concluded that Rule 702 precluded their testimony. The majority has correctly determined, however, that both of the plaintiffs’ experts should have been permitted to testify insofar as their proffered scientific testimony is essential to a decision in the case, the experts are qualified to render an opinion as such, and their proffered testimony is admissible. See W. Va. R. Civ. P. 702.
I write separately to reiterate my position in a similar case decided this term of Court, State ex rel. Jones v. Recht,
Adherence to the guidelines for admitting expert testimony set forth in my Jones sep-erate opinion affords trial courts the opportunity to evaluate proffered scientific evidence to ensure that such evidence is, in fact, admissible while still fulfilling their duty as gatekeepers to preclude the improper admission of evidence that is not reliable and not relevant. See Syl. pt. 4, Gentry,
Because the majority opinion correctly determined the appellants’ experts should have been permitted to testify in this case, I concur in the majority’s decision.
Dissenting Opinion
dissenting:
(Filed December 19, 2007)
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
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.,
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. Gre-gor 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 vero-toxin, 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
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,
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,
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), DaubeH 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,
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,
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 regal’d 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,
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.
As recognized by the Eleventh Circuit Court of Appeals in McClain v. Metabolife Intern., Inc.,
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.” BOR-LAND’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 externalcausation, 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 Gttide 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 .... [hjowever, at another level the confusion can mislead.” 2 Faigman, Modem 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.
While the two methodologies may employ a similar process, that of deduction or elimination, the differences are more than nomenclature, they are substantive for “[vjery different skill sets are usually involved in these two determinations,”
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.”
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.[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).
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
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 preexisting 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
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 maldng 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 “[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 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 opin.,
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.
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 Opin.,
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^]”
“Since Daubeit ... parties relying on expert evidence have had notice of the exacting standards of reliability such evidence must meet.” Weisgram v. Marley Co.,
When this Court adopted the DaubeH standard in Wilt, Justice Neely, 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,
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,
For all of these reasons, I dissent.
. In the case sub judice, the appellee filed a motion for summary judgment at the close of discovery, upon a fully developed record. A hearing was conducted, and the parlies had adequate opportunity to be heard at the pretrial level, before the circuit court made its decision to grant summary judgment for the appellees. Indeed, the majority arrives at its conclusion to reverse the circuit court's ruling, not by using the principles of law enunciated in syllabus point 4, but for entirely different reasons.
. In relying on Cortes—Irizarry v. Corporacion Insular de Seguros,
The Daubert regime can play a role during the summary judgment phase of civil litigation. If proffered expert testimony fails to cross Dau-bert’s threshold for admissibility, a district court may exclude that evidence from consideration when passing upon a motion for summary judgment.
The court also acknowledged that
Though such an opportunity is most easily afforded at trial or in a trial-like setting, courts have displayed considerable ingenuity in devising ways in which an adequate record can be developed so as to permit Daubert rulings to be made in conjunction with motions for summary judgment. See, e.g., Brown v. SEPTA (In re Paoli R.R. Yard PCB Litig.),35 F.3d 717 , 736, 739 (3d Cir.1994)(discussing use of in limine hearings), cert. denied,513 U.S. 1190 ,115 S.Ct. 1253 ,131 L.Ed.2d 134 (1995); Claar, 29 F.3d at 502 (discussing district court’s technique of ordering experts to submit serial affidavits explaining the reasoning and methodology underlying their conclusions.) We do not disparage such practices; we merely warn that the game sometimes will not be worth the candle.
Id. at fn. 3 (emphasis added).
. In their Brief, the San Franciscos label Dr. Todd's testimony as his "verotoxin theory.”
. Dr. Todd’s theory concerning prc-fortned vero-toxin is based on a single 15-year-old study where E. Coli was added to ground beef and held for four days at a temperature of 98.6"F.
. See Federal Judicial Center, Reference Manual on Scientific Evidence 443 (2d ed.2000).
. Courts often confuse differential diagnosis, a technique accepted in the medical field and used by doctors every day, with differential etiology, which is a very different process. "Differential diagnosis refers to the clinical process by which doctors determine the internal disease that is causing a patient's suffering; differential etiology is used for determining the external causes of the problem. In a differential diagnosis, a doctor isolates a disease that is causing the patient’s symptoms, whereas differential etiology isolates an external factor that has caused the internal disease.” Ian S. 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) (internal footnote omitted). See also Edward J. 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.”)(internal footnotes omitted); 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.”)(internal footnotes omitted); Note, Wendy Michelle 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 also 27 Minn. Prac., Products Liability Law § 16.20.
. Faigman, supra, note 6, at 1222.
. See also Imwinkelried, supra, note 7, at 405 ("the two techniques [that of differential diagnosis and differential etiology] are distinguishable. As we have seen, the techniques address fundamentally different questions: the nature of the illness as opposed to the cause of the illness. Moreover, physicians receive more formal training in differential diagnosis than in differential etiology. Lastly, practicing physicians have more experience working with the differential diagnosis technique, since in many cases the cause of the illness is irrelevant to the patient’s treatment. In short, an expert physician’s opinion about the nature of an illness, based on a differential diagnosis, might well be more reliable than the same physician’s opinion about causation, arrived at by differential etiology”) (internal footnotes omitted); Faigman, supra, note 7, at page 1222 ("Differential etiology, however, is anything but a straightforward affair, and most areas of science give it little or no attention.”).
9. It appears that Dr. Gregor in this case primarily, if not solely, identified the Wendy hamburger as the external cause of Mr. San Francisco's symptoms because of the temporal relationship between the eating of the hamburger and the onset of the symptoms.
. Imwinkelried goes on in the succeeding pages of his Baylor Law Review article to describe the process and misconceptions of the differential etiology methodology. One such misconception "relates to the precise ultimate inference which the physician is endeavoring to draw.” Id at 418. He thus elaborates:
The practicing physician employing differential etiology is not attempting to decide whether it is more likely than not that a particular factor caused the plaintiff's illness. The physician faces a treatment exigency: the condition of the physician’s patient may be deteriorating rapidly, and the physician must make a treatment intervention. The physician will not wait until he or she is satisfied that it more likely than not that a particular factor is the cause of the patient's illness.... The physician seeks to isolate the best causal hypothesis. In etiological analysis, the physician could conceivably select a potential cause with a fifteen percent probability if the probabilities for all the other possible causes were lower than fifteen percent. In other words, a differential etiology analysis does not necessarily yield an opinion that is more likely than not that the selected factor caused the illness.
Id. (internal footnotes omitted). In the case at hand, it appears that Dr. Gregor’s diagnosis of Mr. San Francisco’s symptoms was largely based upon what he believed to be a cause, the temporal relationship between the eating of the hamburger and the onset of the symptoms.
. Just what that "food intake history” may have been is not disclosed by appellants. As noted earlier, the appellee contends that Dr. Gregor was not aware of a great number of foods that Mr. San Francisco had eaten within the week before the onset of his symptoms, and which possibly could have caused a foodborne illness.
. This is not to say that I believe a differential diagnosis may never provide a sufficient basis for an opinion as to general causation. Indeed, other courts have recognized that while a differential diagnosis usually does not support an opinion as to general causation, there may be instances where, because of the rigor of the differential diagnosis performed, the expert's training and experience, the type of illness or injury at issue, or some other case-specific circurn-stance, a differential diagnosis is sufficient to support an expert's opinion in support of both general and specific causation. See McCullock v. H.B. Fuller Co.,
. Thus, his opinion was based on the assumption of a fact without any evidentiary support, making it unreliable.