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FORENSIC TOXICOLOGIST:

Establishing Causation in Forensic Toxicology and Forensic Medicine

By Nachman Brautbar, M.D.

In providing medicolegal services and expert testimony, the doctor should use the same standard and method that he is using in daily practice. (This has been the standard applied to physicians by the federal and state courts).

How do physicians who practice medicine establish causation? Do they say to a patient "sorry, sir, I need to use the Daubert criteria before I can tell you that your chest pain can be a sign of an aortic aneurysm?" NO! Do they say to the patient "sorry, sir, I could not find any epidemiological studies and therefore, go home, I cannot treat you?" The methodology used by experts such as the forensic toxicologist who testify must be the same methodology of their daily practice of medicine. (Federal and State Courts) But for some reason in some courts, the medical doctor is forced to relinquish the methods used in practice and use impractical rigorous causation standards.

"Courts with especially demanding standards are misled if they believe that they are fairly representing medical practice. Physicians should respond by correcting courts' misinterpretations of medical practice and assisting in the development of legal standards that encourage thoughtful and informed consideration of medical testimony by judges and juries." Inconsistency in Evidentiary Standards for Medical Testimony, Disorder in the Courts. Jerome P. Kassirer, M.D. Joe S. Cecil, Ph.D., J.D.JAMA, September 2002, V. 288, No 11, p 1382-1387.

From Henle to Bradford Hill

  • The medical scientific community has been struggling with this issue of causation since the early days of Paracelcus.
  • The first criteria for causation were established by Henle and Koch when Henle and his students, including Koch, studied cholera in the 1880's.
  • These criteria have changed through the years undergoing natural evolution.
  • In the 1960's Sir Bradford Hill presented aspects to establish medical causation.
  • For nearly 100 years the Henle-Koch postulates have been used as a reference point in evaluating the causal relationship of a new infectious agent to a clinical disease with which it is associated.
  • The postulates have also served as a point of departure for many concepts of causation of chronic diseases.

For The Forensic Toxicologist Henle-Koch Postulates seem to be the Answer

  • The parasite occurs in every case of the disease in question and under circumstances which can account for the pathological changes and clinical course of the disease.
  • It occurs in no other disease as a fortuitous and nonpathogenic parasite.
  • After being fully isolated from the body and repeatedly grown in pure culture, it can induce the disease anew.
  • Based on Rivers' translation (1937).

Were Koch's criteria indeed safe-proof for causation? Did the criteria satisfy forensic toxicology and forensic medicine?

  • At the same time there were a number of infectious agents which did not meet all the criteria and yet which Koch felt were strongly implicated in the causation of the disease.
  • These included the bacteria isolated from typhoid fever, diphtheria, leprosy, relapsing fever, and Asiatic cholera.
  • After being fully isolated from the body and repeatedly grown in pure culture, it can induce the disease anew.
  • The major problem of fulfillment was the inability "to produce the disease anew" in an experimental host.

FORENSIC TOXICOLOGY, FORENSIC MEDICINE AND PHYSICIANS DECIDED: Koch's Criteria Not A Check Box for Causation

  • Another problem limiting the application of the Henle-Koch postulates was the inability to grow many presumed human pathogens in the laboratory.
  • This applied to many parasitic diseases such as malaria, as well as to leprosy.
  • Thus, even at the time they were presented, the Henle-Koch postulates were never recommended as rigid criteria of causation and failed to apply to many diseases at the time when a causal relationship seemed almost unequivocal.
  • Koch himself felt that fulfillment of the first two postulates might be sufficient evidence of causality.

Koch's criteria have changed over a period of 100 years to account for viruses, epidemiology and cancers. Instead the Bradford Hill aspects were suggested as "criteria" to establish causation for medical doctors, forensic toxicologists and medical toxicologist.

INDEED, LET US EXAMINE SOME OF THESE "CRITERIA"

  • TEMPORALITY.
  • This criterion is inarguable, insofar as any claimed observation of causation must involve the putative cause C preceding the putative effect D.

Indeed, Professor Rothman in his Textbook of Modern Epidemiology stated that if any of these aspects of Hill are important, then temporal relationship is the one.

Professor Rothman Indeed Concludes

  • As is evident, the standard of epidemiologic evidence offered by Hill are saddled with reservations and exceptions.
  • Hill himself was ambivalent about the utility of these "standards" (he did not use the word criteria in the paper).
  • On the one hand, he asked "In what circumstances can we pass from this observed association to a verdict of causation?"
  • Yet, despite speaking of verdicts on causation, he disagreed that any "hard-and-fast rules of evidence" existed by which to judge causation (Like a "check box" or "rate of error").

Indeed, Professor Rothman in his Textbook of Modern Epidemiology stated that if any of these aspects of Hill are important, then temporal relationship is the one.

My recommendation for the practicing forensic toxicology internist, occupational physician, internist and toxicologist; follow your practice principles:

  • Review all records.
  • Review all environmental data available, MSDS, hydrogeological data, industrial hygiene data. (Carefully watch for dates of testing).
  • Use the methodology used by clinicians: Rule out differential diagnosis (medical records, testing, examination of the patient if possible).
  • Evaluate the available scientific, regulatory literature regarding the type of toxic chemicals in question.

Establish duration of exposure. Commonly we see the patients years after the major toxic exposure occurred. Evaluate depositions, statements of co-workers for symptoms during the exposure. Case reports and experimental animal studies should be relied on since in the majority of the cases no manufacturers, chemical companies, EPA or ATSDR have conducted "large scale" epidemiological studies on every chemical in question.

Ask your experts to clarify and explain their methodological approach by describing it in terms that judges and juries will understand like: How did you get from Point A (exposure to a toxic agent) to Point B (disease process or risk).

The following will demonstrate the use of differential diagnosis, physical examination, history and extrapolation from symptoms to levels of exposure, and how to win a Daubert motion.

SO WHAT IS THE PROCESS OF ESTABLISHING CAUSATION?

There is no check box for causation. Get a good history, evaluate the differential diagnosis, study the medical records, study the chemical records, and if available, industrial hygiene data (relevant to the date of exposure), study the literature if applicable in humans or experimental animals, and explain your method, extrapolation and how you arrived from point A exposure to point B illness.

Methodology Relying on Alternative Causation for The Forsenic Toxicology and Medical Toxicology Expert
Differential Diagnosis:

Differential diagnosis is an important step in the methodology of explaining how you get from Point A to Point B. It is a basic method used daily in the practice of medicine. This step in establishing causation is relevant, reliable and your expert must rely on it.

Important Case That Every Forensic Toxicologist, Toxicologist and Internist Should Know:
James Curtis Westberry
(IMPORTANCE OF DIFFERENTIAL DIAGNOSIS)

  • United States Court of Appeals 4th Circuit, 178 F3d 257, 1999 US APP.
  • In this case defendants sought to exclude plaintiff's expert testimony because the doctor did not have epidemiological studies, no peer reviewed literature, no animal studies, and no laboratory data to support his opinion that inhalation of talc caused Westberry's sinusitis. Instead, the doctor relied on differential diagnosis is a standard scientific technique in identifying the cause of a medical problem.

The Appellate Court Opined:

  • A differential diagnosis is a standard scientific method in identifying the cause of a medical problem.
  • A reliable differential diagnosis if formed after history taking, physical examination and review of clinical tests.
  • Temporal connection between exposure to a given chemical and subsequent injury is so compelling as to dispose with the need for reliance on standard method of toxicology.

"In summary,... a reliable differential diagnosis provides a valid basis for an expert opinion on causation."

Levels of Exposure

  • Dose - In the majority of cases, levels of exposure are not available for one reason or another. Here comes in the skill of the doctor, extrapolating from symptoms developing at time of exposure to a given chemical to levels of exposure.
  • A reliable differential diagnosis if formed after history taking, physical examination and review of clinical tests.
  • Temporal connection between exposure to a given chemical and subsequent injury is so compelling as to dispose with the need for reliance on standard method of toxicology.

AN IMPORTANT CASE EVERY FORENSIC TOXICOLOGIST, TOXICOLOGIST AND INTERNIST SHOULD KNOW:
Mike Curtis et al v. M&S Petroleum, 174F3d 661, No 97-60685 May 13, 1999 (Extrapolation from symptoms to levels of exposure).

  • In this case, defendants sought to exclude the doctor's testimony on the basis that the doctor had no levels of exposure. This was a case of exposure to benzene. The doctor obtained a history that when handling benzene, the patient developed dizziness.
  • The scientific literature quoted, demonstrated that dizziness at the time of handling benzene is equivalent to levels of 300-400 PPM (very substantial levels). The appellate court opined that the doctor had more than a paucity of facts, and allowed his testimony.
  • Another example is odor recognition. The EPA and ATSDR have published a list of chemicals and at what levels the patient will recognize the smell. For an example, odor recognition of benzene is anywhere from 60-90 ppm. This concept has recently defeated a Daubert motion in St. Bernard Parish, Louisiana (Doerr case).

AN IMPORTANT CASE THAT EVERY EXPERT IN FORENSIC TOXICOLOGY, FORENSIC MEDICINE, TOXICOLOGY SHOULD KNOW:
Richard Asad et al v. Continental Airlines, US District Court Northern District of Ohio, Case No. 1:99 CV 2194
EXTRAPOLATION FROM SYMPTOMS TO LEVELS OF EXPOSURE

  • Another example is carbon monoxide. In this case, defendants sought to exclude the expert's testimony since there were no "levels." The doctor reviewed the data and found out that when the patient was exposed to carbon monoxide she developed headaches and dizziness. The doctor provided literature allowing extrapolation from symptoms to levels of exposure. The Daubert motion was defeated.

THE IMPORTANCE OF DIFFERENTIAL DIAGNOSIS
Max Clausen (Max Clausen et al( dba Clausen Oysters) v M/V New Carissa et al, No. 01-35928, No. 01-36079, UNITED STATES COURT OF APPEALS FOR THE NINTH CIRCUIT,339 F.3d 1049; 2003 U.S. App. LEXIS 16436; 61 Fed. R. Evid. Serv. (Callaghan) 1474; 56 ERC (BNA) 1965; 2003 Cal. Daily Op. Service 7193; 2003 Daily Journal DAR 9017 March 4, 2003, Argued and Submitted, Portland, Oregon August 12, 2003, Filed)

(The Importance of a Differential Diagnosis)
In this case, the defendant moved to exclude the experts testimony based on Daubert. The Court of Appeal opined that the doctor performed differential diagnosis. Differential diagnosis or differential etiology is a standard scientific technique for identifying the cause of a medical problem by eliminating the likely causes until the most probable one is isolated "A reliable differential diagnosis taking of medical histories,... generally is accomplished by determining possible causes for the patient's symptoms and then eliminating each of these potential causes until one that cannot be ruled out or determining which of those that can not be excluded is most likely. Differential diagnosis is a common scientific technique and federal courts, generally speaking, have recognized that a properly constructed differential diagnosis is admissible under Daubert... we recognized in Kennedy v. Collagen Corp., 161 F.3d 1226 (9th Cir. 1998), that a reliable differential diagnosis passes muster under Daubert. See Westberry, 178 F.3d at 263 (citing Kennedy for the proposition that the Ninth Circuit has held that "a medical opinion on causation based upon a reliable differential diagnosis is sufficiently valid to satisfy" Rule 702);...The district court rejected the expert's testimony because he had not relied on specific epidemiological or animal studies proving Zyderm causes SLE and because there existed no consensus in the medical community on the issue. Id... We reversed the district court, and held that the proffered evidence was reliable, and therefore admissible, because it was "based on [the expert's] knowledge of the connection between collagen and various autoimmune disorders, combined with [the expert's] observation of [the plaintiff's] injuries and her medical history and laboratory tests." Id. At 1229-30. We noted that the lack of studies linking Zyderm and SLE was not fatal to its admissibility: "The fact that a cause-effect relationship between Zyderm and lupus in particular has not been conclusively established does not render [the expert's] testimony inadmissible." Id. At 1230. Accordingly, the district court "abused its discretion in excluding [the expert's] testimony." Id. At 1227." Clearly the Clausen Court opined that the absence of epidemiological studies is not detrimental to causation analysis based on the principles of 1) review of records; 2) history and chemical data sheets; and 3) differential diagnosis.

IMPORTANCE OF TEMPORAL RELATIONSHIP

AN IMPORTANT CASE THAT EVERY EXPERT IN FORENSIC TOXICOLOGY, FORENSIC MEDICINE, TOXICOLOGY SHOULD KNOW: IMPORTANT ROLE OF TEMPORAL RELATIONSHIP

Katie Bonner. (Katie Bonner, Plaintiff/Appellee, Esau Bonner, Plaintiff, v. ISP Technologies, Inc., Defendant/Appellant, Crawford & Company, Inc., Movant. No. 00-3458, UNITED STATES COURT OF APPEALS FOR THE EIGHTH CIRCUIT 259 F.3d 924; 2001 U.S. App. LEXIS 17252; 57 Fed. R. Evid. Serv. (Callaghan) 15; 32 ELR 20008 May 16, 2001, Submitted August 3, 2001, Filed)

The trial court was asked to disallow the testimony of the expert because the "testimony was unreliable." The Appellate Court focus that the expert relied on a methodology of 1. temporal connection between the exposure and the disease; 2. animal studies in regards to the chemical; 3. studies with chemicals with similar structures; 4. study of the mechanism by which the chemical affects health in this case; 5. medical records. The appellate Court states "under some circumstances a strong temporal relationship is a powerful evidence of causation." When a person is dowsed with chemical X and immediately thereafter developed symptom Y, the need for published literature showing a correlation between the two may be lessened.

IMPORTANCE OF EXTRAPOLATION FROM OTHER STUDIES

AN IMPORTANT CASE THAT EVERY EXPERT IN FORENSIC TOXICOLOGY, FORENSIC MEDICINE, TOXICOLOGY SHOULD KNOW

(Extrapolation from other studies)
Sonia Bocanegra (SONIA BOCANEGRA, versus VICMAR SERVICES, INC; ET AL, Defendants, BOAKE SANDOZ D/B/A/ SANDOZ MAINTENANCE SERVICE, CLARENDON NATIONAL INSURANCE COMPANY, AND RUSSELL A. SERGENT A/K/A/ RUSSELL A. SARGENT, Defendants-Appellees. No. 01-31121 UNITED STATES COURT OF APPEALS FOR THE FIFTH CIRCUIT 320 F.3d 581; 2003 U.S. App. LEXIS 2960; 60 Fed. R. Evid. Serv. (Callaghan) 804, February 19, 2003, Decided)

Another example is marijuana cases in regards to levels. In this case, the trial judge excluded the testimony of the expert because he did not know the quantity or quality of the marijuana ingested. The Appellate Court reversed, and said that the expert methodology of extrapolating from other studies was reliable. The court also opined that the testimony of the expert that people smoke marijuana to get high. Therefore, the lack of quantity should not make the expert opinion inadmissible.


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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