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Causation, Science And The Law:

Industrial & Environmental Chemical Toxicity

By Nachman Brautbar, M.D.

*This manuscript also summarizes previous publications by Dr. Brautbar, including Science And The Law, Journal of Clean Technology, Environmental Toxicology & Occupational Medicine, Volume 6, 1997; Science And The Law: Scientific Evidence, Causation, Admissibility, Reliability. "Daubert" Decision Revisited, Toxicology & Industrial Health; Establishing Causation in Forensic Medicine (From Henle To Bradford Hill), Journal of Clean Technology, Environmental Toxicology & Occupational Medicine, Volume 6, 1997; and Scientific Evidence, Book Chapter.

About The Author
Dr. Nachman Brautbar specializes in Internal Medicine, Occupational Medicine and Forensic Toxicology. He is a Clinical Professor of Medicine and he is a member of the American Society of Toxicology, the American College of Toxicology, and the American Society of Internal Medicine. He has published over 240 scientific peer reviewed papers and book chapters in the fields of Forensic Toxicology, Forensic Medicine, Pharmacology, Internal Medicine, Immunology and Nephrology. Dr. Brautbar is a treating physician and in his practice he addresses such issues as the use and effects of the drug Phen-fen, in addition to lung disease, asbestosis, chemical injury, solvent-related toxicity and occupational diseases. Dr. Brautbar has testified as an expert in some major toxic torts nationally.

Forensic Medicine is the application of medicine to the law. The forensic medicine specialist has to answer several questions such as what causes a medical condition. When was it caused. The forensic toxicologist is in the best position to answer questions on causation. The forensic toxicologist is in the best position to address these issues in forensic medicine. The forensic toxicologist is a medical doctor with expertise in toxicology and occupational medicine.

Occupational and environmental exposure to potentially toxic chemicals has been reported more frequently in the last five (5) years, most likely as the result of 1) increased public awareness, 2) improved reporting by physicians, 3) unlimited access to the information data banks, 4) more efficient regulatory support, 5) increased recognition by treating and evaluating physicians.

A physician who evaluates and treats patients with toxic exposure has to address the issue of causation. This issue of medical causation in toxic exposures has been the subject of ongoing scientific evolution over the last forty (40) years. As science evolves so does the understanding of causation and scientific evidence.

The Methodology For Establishing Cause And Effect
The evaluating and treating doctor has to establish cause and effect in the process of providing treatment, diagnosis or the evaluation of a population of patients for the purposes of consultations for forensic toxicology opinions. The methodology for establishing causation in the medical profession is not new and has been established and published in various texts, international and national conferences, and scientific peer-reviewed papers. Despite the fact that the methodology required to establish causation in toxic exposures has been well-described, the applicability of that methodology in the forensic medicine (medical-legal) arena has been a subject of deep division among experts, attorneys, and the judicial system.

Forensic medicine by its nature is subject to disagreements, especially in our adversarial judicial system. It is not unusual to find equally experienced and credentialed experts relying on the same literature and expressing diametrically opposed scientific opinions. The argument of what methodology is applicable, especially in toxic exposures disease process, is so passionate that it is no surprise that the court system in these types of cases, specifically toxic exposures, has tried to resolve this passionate argument by applying what was supposed to have meant some "criteria" to filter out what is sometimes (justifiably and not justifiably) classified as "junk science' (expert on both sides of the issue, i.e. defense and plaintiff experts have been labeled as "unreliable" based on some judicial pretense). The most recent editorial in the Journal of the American Medical Association criticizes this approach by some courts and clearly states "Courts with especially demanding standards are m isled if they believe that they are fairly representing medical practice." (Kassirer, JP; Cecil JS; Inconsistency in Evidentiary Standards for Medical Testimony, Disorder in the Courts, JAMA, September 18, 2002, Vol 288, No. 11, pgs 1382-1387 )

The famous or by some experts unreasonable "Daubert(1) decision" stated that the judge is the gatekeeper as far as the experts' preferred testimony. The Daubert court has provided several criteria for expert's testimony admissibility. : (1) whether the theory or technique used by the expert can be, and has been, tested; (2) whether the theory or technique has been subjected to peer review and publication; (3) the known or potential rate of error of the method used; and (4) the degree of the method's or conclusion's acceptance within the relevant scientific community.

Since the famous Daubert decision much confusion, and at times misunderstanding of causation, scientific evidence, and expert testimony reliability have arisen, nicely summarized in the statement by Professor Capra in his paper: "This schizophrenic aspect of Daubert...".(2) From review of what always used to be the scientific basis for causation and careful review of some of the recent cases "utilizing" the Daubert, it is no surprise that many courts have been divided in the application of those criteria when it comes to admissibility of expert testimony.

This deep division and what is described by some scholars as the "schizophrenic" aspect of Daubert has been recently experienced by me as a lecturer for State Court Judges from across the United States at the National Judicial College in Reno (November of 1998) in a session specifically addressing science in the courtroom. After I completed my presentation, which essentially addressed the methodology to be utilized and which is used by medical experts in order to establish causation, a very lively, intellectual, practical and productive discussion took place, the Honorable Judge Andre M. Davis and Attorney Anthony Roisman (who is well known in the environmental law circles) moderated the discussion. One of the judges from the State of Texas posed a question as follows, "I am a State Court Judge in a farming community where a relatively new chemical has been used for the last 2 years. No peer-reviewed literature is yet available since this is a new chemical, the material safety data sheets lack long-term information due to the fact that this is a new chemical, and several cases have come up where credible patients presented with history of exposure and evidence of injury." The judge further continued, "The doctor who treated those patients opined that the injuries are the result of exposure to this chemical (which in animals can cause a similar type of injuries), however defendants motioned the court to exclude the doctor's testimony based on the Robinson decision,(3) (which essentially applies Daubert criteria to a state court law in Texas)." The judge further asked, "The patient's are credible, the doctor is credible, there is a chain of events and temporal relationship, and treatment was required after the exposure to this chemical, but on the other hand I have these criteria established in the Daubert decision and applied to the state court in Texas under the Robinson decision." The scenario described by the Honorable Judge is not a unique one and in actuality is a very common one, one that physicians, insurance companies, attorneys, and courts throughout the country struggle with on a daily basis. If one has to take the rigid inflexible interpretation of the Daubert decision (which initially was supposed to be much more liberal and not inflexible) then, regardless whether the doctor ruled out other diseases, regardless whether the doctor reviewed medical records and found no evidence for other causes, other than the exposure, no matter if the material safety data sheets described this chemical as capable of causing injuries to the lungs and upper airways in experimental animals, the mere fact that this is a new chemical and there is no "peer-reviewed scientific literature published" addressing that specific chemical to these specific injuries there is no redress for the injured patients. On the other hand, if one adopts the methodology which is used by medical doctors, specifically, history, differential diagnosis, diagnostic studies, ruling out other causes, review of medical records, and review of the scientific literature, reliance on this methodology has served the medical profession for many years clearly establishes causation in this specific case given this theoretical scenario. Indeed the Federal Courts stated that the method of the doctor should not be different then what is used in the daily practice of medicine. After all, you do not expect your doctor to say "I need a peer reviewed paper with statistical analysis to tell if you are sick!! (You will be surprised on what some of the most outrageous Daubert decisions were based on). Or maybe not? To lead us in this quandary, I have chosen to quote parts of the Honorable Justice Dennis' dissenting opinion and the appellate's decision in Bob T. Moore v. Susan Moore.(4) Judge Dennis opined that the majority opinion (of the appellate court in this case) creates a "schism" between this court (the 5th Circuit Court) and other circuits, and state court of last resort, and disregards the teachings of federal evidence law scholars. The 2nd, 3rd, and 4th Circuits had held that a clinical physician may, consistently with Daubert, express an opinion, based on clinical medical methodology generally accepted within that discipline, that the particular toxic substance caused the patient's disease or death without hard, scientific collaboration under an inflexible application of the Daubert factors. Judge Dennis relied, among others, on the 2nd circuit decision in the McCulloch case(5) where the court rejected defendant's argument for exclusion of the clinical physician opinion as scientifically unfounded that glue fumes caused the plaintiff's respiratory symptoms and throat polyps. In that case, the evaluating doctor based the opinion upon his use of clinical medical methodology without any "hard science" or strict Daubert factor related basis. The defendant in that case argued that the doctor could not point to a single piece of medical literature that said that glue fumes caused throat polyps. The Court in that case, however, stated that the doctor based his opinion on a range of factors which include 1) his current treatment of the patient, 2) medical history, 3) pathological studies, 4) review of Material Safety Data Sheets, 5) the doctor's training and experience, 6) the use of scientific analysis known as differential etiology (which requires listing possible causes and then eliminating all causes except one) and 7) reference to various scientific and medical treaties. While there is no doubt in my mind that some conservative courts would hold the opinion that the doctors methodology in the McCullough case was "junk science" because there was "no peer review" of literature addressing that specific glue fumes, the court clearly stated that the doctor relied on the methodology used by medical doctors, accepted methodology used in the same discipline, mainly medicine. Judge Dennis also relied on the Benedi court (6) where the court clearly stated, "We will not declare the clinical medicine methodologies invalid and unreliable in light of the medical community's daily use of the same methodologies in diagnosing patients." I believe that Judge Dennis' opinion summarizes many traditional legal and medical scholars opinions as far as the methodology to be relied upon by medical experts. Judge Dennis' following statement sheds much light on what has been made so confusing and complicated by extremely conservative, and in my opinion, unreasonable parties. Specifically, Judge Dennis' opinion that, "the embank majority, in my opinion, makes several errors of law, the most serious of which is its holding that the clinical medical expert whose opinion is based on the sound cooperation of the principles of methodology of his or her discipline, cannot reliably testify as to the causal relationship between an individual's exposure to a chemical compound and his or her subsequent onset of symptoms and disease. As a result of this error of law in others, the embank opinions subverts the liberal thrust of the federal rules of evidence and the principles enunciated in Daubert by locking the gate on causation evidence derived through the principles and methodology of clinical medicine." Judge Dennis' opinion indeed represents (at least in my opinion) a rationale assessment of the methodology used to establish causation, and as such, admissibility. Indeed, as we will see later in this manuscript, the U.S. Supreme Court essentially supports this approach in its recent Kumho Tire decision.

The most recent Supreme Court decision in Kumho Tire Co., LTD, et al, v Carmichael, et al,(7) dealt with these specific issues and provided reasonable and ethical interpretation of the Daubert criteria. Essentially, what the Supreme Court opined is the following: While the Daubert criteria are intended to serve as a tool to examine the reliable basis of an expert's prior to admitting the expert's testimony (applied to all experts), the Daubert factors are not definitive nor inclusive, and the Daubert factors may or may not be pertinent depending on the specific case in front of the court. The court specifically stated, "We agree with the Solicitor General that the factors identified in Daubert may or may not be pertinent in assessing reliability, depending on the nature of the issue, the experts particular expertise, and the subject of his testimony." The court further stated that "Daubert itself is not to the contrary. It made clear that its list of factors was meant to be helpful, not definitive." The court further stated, "It might not be surprising in a particular case, for example, that the claim made by a scientific witness has never been of peer review, for the particular application at issue may never previously have interested any scientist. Nor, on the other hand, does the presence of Daubert's general acceptance factor help show that an expert's testimony is reliable when the discipline itself lacks reliability, as, per example, do theories grounded in any so-called generally accepted principles of astrology or necromancy." The court further stated, "The objective of that requirement (the importance of Daubert gatekeeping requirement) is to insure the reliability and relevance of expert testimony. It 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." The court further opined, "Rather, we conclude that the trial judge must have considerable leeway in deciding in a particular case how to go about determining whether particular expert testimony is reliable. That is to say, a trial court should consider the specific factors identified in Daubert where they are reasonable measures of the reliability of expert testimony." Essentially, the Kumho decision clarifies the Daubert decision, and clearly states that it is the judge's discretion to decide when and if to use the Daubert criteria and that the criteria are construed in a flexible manner. (While conservative parties were rushing into extremes of interpretation, the wording of the Kumho Tire court is clear: The judge has the discretion to decide when to apply Daubert, when Daubert is not relevant, and when to admit an expert's testimony based on professional experience and methodology used in that specialty.)

If we go back to my experience at the National Judicial College in Reno, and the question that the Judge from Texas posed to me, in my opinion, and in light of the Kumho decision, it is within the judge's discretion to decide whether for this particular chemical which is new, there is no peer-reviewed literature, there is no known range of error, the accepted methodology of clinicians is the litmus of admissibility of the doctor's methodology.

Establishing Causation

Doctors specializing in forensic medicine medical toxicology and internal medicine will probably be in the best position to address these issues.

Hannelore Anderson Decision


The Kumho Tire court decision and its logic has been most recently applied in the case of Hannelore Anderson v Quality Stores, Inc, et al.(8) In that opinion the 4th Circuit U.S. Court of Appeals ruled on 06/14/99 that the opinions of the experts offered in a chemical exposure case were based on a reliable differential diagnosis and a strong temporal relationship between exposure and the onset of symptoms and therefore should have been admitted. Initially the issue in the case was that the District Court entered summary judgment for Quality (defendants), holding that the experts' opinions were not reliable because there was no evidence of quantifying the levels of exposure and finding that in the absence of additional testimony on causation the evidence was not sufficient to raise a genuine issue of fact. The U.S. Court of Appeals for the 4th Circuit clearly disagreed with that approach. In their opinion they stated that in a previous case on 05/20/99, Westbury v Gislaved Gummiab,(9) they upheld that an expert's opinion based on differential diagnosis and strong temporal relationship between exposure and the onset or worsening of symptoms is sufficiently trustworthy to satisfy the reliability prong of Rule 702. They have essentially followed the line of thinking and reasoning as did the honorable Judge Dennis and as did the other court, specifically that a medical doctor relying on differential diagnosis, temporal relationship, and general knowledge on the generic effects of a chemical, is reliable and admissible. In the Westbury case, the appellate court clearly stated that, "The temporal relationship between Westbury's exposure and the onset and worsening of his sinus disease provided support for Dr. Eisenhower's opinion that talc was the source of the problem."

In my opinion, the Supreme Court decision in the Kumho cases is a reasonable "relaxation" of the Daubert decision (which in my opinion has been "used" by defendants, and at times misunderstood by plaintiffs), and provides a reasonable middle ground for the judge to be the fair gatekeeper of expert's testimony with the understanding that the judge should use flexible criteria.

The causation issue does not always equal etiology, meaning, a condition may have several causes but "unknown etiology." This is confusing to the average practicing physician. The expert in medical toxicology or forensic medicine by the nature of the practice, are used to the causation analysis.

Suggested Reading

  1. Science and the Law; Journal of Clean Technology, Environmental Toxicology & Occupational Medicine, Volume 6, No. 1:91-100, 1997
  2. Science And The Law: Scientific Evidence, Causation, Admissibility, Reliability. "Daubert" Decision Revisited, Toxicology & Industrial Health
  3. Establishing Causation in Forensic Medicine (From Henle To Bradford Hill), Journal of Clean Technology, Environmental Toxicology & Occupational Medicine, Volume 6, 1997
  4. Capra, DJ, The Daubert Puzzle, Georgia Law Review, Spring 1988, 32:699-781
  5. Rom, WN, Causation, Textbook of Environmental and Occupational Medicine, 2nd Edition, 1992, Little Brown & Co., 38-47
  6. Maxcy-Rosenau, Public Health and Preventive Medicine, 12th Edition, 1992, Appleton & Lange, 31-34


  1. Daubert v. Merrill Dow Pharmaceuticals, 1993, 509 U.S. 579, 113 S. Ct 2786.
  2. Capra, DJ, The Daubert Puzzle, Georgia Law Review, Spring 1988, 32:699-781.
  3. E.I. Dupont de Nemmours and Company Inc., Petitioners v C.R. Robinson and Shirley Robinson, Respondents, No. 94-0843, Supreme Court of Texas, Decided 06/15/95, RE: Hearing, Overruled 07/08/96
  4. Bob T. Moore and Susan Moore v Ashland Chemical Inc, et al, Case Number 925-20492, Appealed from the U.S. Distric Court for the Southern District of Texas, 08/14/98.
  5. McCullock, G, v H.B. Fuller Company, United States Courts of Appeals for the 2nd Circuit, No. 1188, No. 94-7883, Decided 07/27/95
  6. Antonio Benedi v McNeil-P.P.C., Incorporated, United States Court of Appeals for the Fourth Circuit, No. 94-2596 (CA-94-345-A), Filed 10/26/95
  7. Kumho Tire Co., Ltd., et al v. Carmichael et al, United States Court of Appeals for the 11th Circuit, No. 97-1709, 1999.
  8. Hannelore Anderson v Quality Stores, Inc, et al, United States Court of Appeals for the 4th Circuit, No. 98-2240, 06/99.
  9. Westbury v Gislaved Gummiab, United States Court of Appeals for the 4th Circuit, No. 98-1540 (L), 05/99.

Dr. Brautbar is a board-certified internist and nephrologist, and certified in forensic medicine. If you are interested in retaining Dr. Brautbar for forensic and expert witness testimony services, please submit the Contact Form.

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