Daniel W. Shuman, Southern Methodist University School of Law
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Abstact
Introduction
The Traditional Adversarial System Approach
The Gatekeeping Approach
Much Ado about Little: The Effect of Daubert, Joiner, and Kumho Tire on Claims of Medical Expertise
Civil Litigation
Criminal Litigation
Barriers to a more Informed Application of Science-Based Medical Evidence in Law
Where Do We Go from Here? Constraints and Concerns
Conclusion
References and Notes
As the practice of science-based medical evidence has challenged the medical profession to consider the scientific bases for its methods and procedures, on a seemingly parallel path, the United States Supreme Court's 1993 decision in Daubert v. Merrell Dow Pharmaceuticals has challenged the legal system to consider the science underlying claims of medical expertise. This article examines how the legal system has responded to that challenge and why the response has been more limited than many had expected; the implications of the legal system's approach to scrutiny of claims of medical expertise for the practice of science-based medical evidence; and, the central elements of any meaningful change in legal assessments of expertise in medicine and health care.
Physicians offer expert testimony in a wide variety of civil and criminal proceedings that may directly involve the provision of health care (e.g., the standard of care in medical malpractice claims), that may indirectly involve the provision of health care (e.g., the prognosis of a claimant injured in an automobile accident), or that may not at all involve the provision of health care (e.g., the cause of death in a homicide prosecution or toxic tort claim). Even if a physician's provision of expert testimony is so closely tied to the provision of health care as to constitute the practice of medicine (Simon and Shuman 1999), no formal mechanism exists within the health care professions to approve the qualifications of purported experts or the reliability of their methods and procedures beyond the generic license to practice. Thus it falls to the courts to fashion mechanisms to address these purported experts' qualifications and their methodologies. This article addresses the mechanisms that courts have fashioned and the results they generate for science-based medical evidence. Whether the law regards as expert what a majority of the medical profession or particular groups of physicians may regard as expert can have a profound affect on the outcome of legal proceedings as well as the practice of medicine. As the practice of science-based medical evidence has grown, emphasizing "a structured critical examination of medical research literature, and a relative deemphasis of anecdote and personal heuristics" (Cynthia D. Mulrow and Kathleen N. Lohr in this special issue), its potential impact on the law and the law's potential impact on the practice of science-based medical evidence will be shaped in no small way by how the law assesses expertise in medicine and health care.
To understand how the law addresses claims of expertise in medicine and health care requires an understanding of two very different ideals about trials that vie for dominance in the U.S. judicial system. These two ideals, represented by the traditional adversarial approach and the gatekeeper approach, reflect two different ways of accommodating the tension among core values at stake in the dispute resolution process-accuracy, fairness, efficiency, consistency, and accessibility. The strength of the support for these differing accommodations has vacillated over time and frequently has varied within a jurisdiction according to the evidence at issue or the context in which admission is sought. For example, while the traditional adversary approach retains its hold in criminal cases and most categories of civil cases including medical malpractice cases in most jurisdictions, the gatekeeper approach has recently made substantial inroads in toxic tort and products liability cases in many of those jurisdictions. Accurate prediction of how courts will respond to a particular claim of expertise in medicine or health care, or a meaningful attempt to change that approach, requires an understanding of the ideals represented by the traditional adversary and gatekeeper approach and their effect on the admission of evidence.
Thus this article begins by exploring these models and their implications for the admissibility of science-based medical evidence. Of the two, the language of the gatekeeper model, invoking falsifiability, error rates, and peer review, appears most compatible with the concept of science-based medical evidence. Accordingly, the article then examines the impact of the cases that have ushered in the gatekeeper model on the admissibility of claims of medical expertise in both civil and criminal litigation. Concluding that the formal adoption of the gatekeeper model has had only a limited effect on the admissibility of claims of medical expertise-largely in raising the threshold for plaintiffs in products liability and toxic tort claims, the article then addresses the temporal, tactical, and philosophical barriers to a more informed application of science-based medical evidence in law. Finally, the article suggests several strategies for a more informed judicial response to claims of expertise in medicine and health care, including more rigorous scrutiny of expert testimony across the judicial spectrum, greater attention to the substantive legal standards that drive the need for expert testimony, and increased efforts to address the scientific education of lawyers.
Although critics often use the word "adversarial" pejoratively, the American legal system rejects the civil law's inquisitorial model and embraces the adversarial model as a novel vehicle to achieve a panoply of important social goals. The adversarial model assumes we are more likely to uncover the truth about a contested event as the result of the efforts of the parties who have a self-interest in the discovery of proof and exposing the frailties of an opponent's proof than from the efforts of a judge charged only with an official duty to investigate the case (Hazard, Fleming, and Levesdorf 1992). The adversarial model also assumes that the parties' participation in the investigation and telling of their story, and the use of a decision maker who is independent of the investigation of the case, will enhance support of the judicial system and confidence in its decisions (Tyler 1992). The model is also touted as an essential ingredient of our American democracy. The American legal system's extensive use of the jury system and its faith in the competence of jurors to resolve complex questions is based on a belief in the wisdom of common men and women, incorporation of community values into the trial system, and democratic values imbued by trusting governmental action to private citizens (Lempert 1981).
The rules that implement the adversarial model incorporate these goals and illuminate some of the fundamental tensions they present. Consider the rule describing the goals of the Federal Rules of Evidence, which govern the admissibility of evidence at trial in the federal courts: "These rules shall be construed to secure fairness in administration, elimination of unjustifiable expense and delay, and promotion of growth and development of the law of evidence to the end that the truth may be ascertained and proceedings justly determined"(Federal Rules of Evidence Rule 102). Securing fairness, avoiding unjustifiable expense and delay, ascertaining truth, and justly determining proceedings are important but not invariably consonant goals. For example, the cost of ascertaining truth in some cases may be beyond the means of the parties or require a significant delay that prevents the speedy resolution of criminal charges or civil claims. Thus the rules recognize truth as an important, concurrent goal of the adversary system.
The adversary system has long recognized, as an important component of our democratic tradition, the wisdom of identifying the witness's bias and prejudice as well as the decision maker's. The adversarial model assumes that the believability of all witnesses, both lay and expert, is affected by their values and beliefs, and rejects the notion that impartiality or neutrality exists. Nonetheless, the use of partisan rather than court-appointed experts has been the subject of much intense criticism (Champagne et al. 2001).
One criticism of the adversary system claims that the information presented to the courts by privately retained experts is biased because attorneys seek out experts who will best assist their case and not necessarily because the experts represent mainstream science. A related criticism claims that the use of retained experts provides judges little control over the use of nonmainstream experts. Critics also claim that the use of privately retained experts increases the number of experts and therefore the expense of using experts. And critics claim that a system in which retention turns on the support an expert may provide for the case is a built-in incentive for experts' opinions to accommodate the interests of their attorney-employers. Notwithstanding these criticisms and the authority that courts enjoy to appoint experts, the use of court-appointed experts is exceptional in the American judicial system.
The U.S. legal system's failure to embrace the use of court-appointed experts as a panacea for the ills of retained experts is rooted, in large part, in its skepticism that experts' biases and prejudices are solely a product of the adversary system. "It is slightly mysterious that it should be thought that experts are venal mountebanks when engaged by the parties but transformed into paragons of objectivity when employed by the courts" (Howard 1991: 101; Champagne, Shuman, and Whitaker 1996). Thus, as science has wrestled with the way in which history, training, and values have bounded scientific knowledge (Kuhn 1970), the American adversary model has wrestled with proposals that would place the search for truth in the hands of scientists in science courts or other procedures that may not adequately expose the scientist's values and beliefs (Jacobs 1993). Wary that "there is no such thing as a neutral, impartial witness" (Diamond 1959: 229-230), the adversarial model has regarded the role of the jury and rules of admissibility that encourage informing the jury of all relevant evidence as critical to ascertaining truth and justly determining proceedings (Thayer 1898).
The role of the judge, jury, lawyers, and experts is central to the operation of the adversarial model. The adversarial model assumes that the parties' lawyers will be skilled, zealous advocates who drive the system investigating and presenting favorable evidence and challenging unfavorable evidence. Unlike the inquisitorial model, in the traditional adversary model the judge is not expected to conduct an independent investigation and determine the evidence that will be used to decide the case, but is instead expected to ensure that the procedures are fair and the parties have an equivalent opportunity to gather evidence and present their case. Although there is great ambivalence about the competence and biases of juries in legal and popular culture (Shuman and Champagne 1997), the traditional adversarial model relies on the intelligence and common sense of the jury, as reflected in this statement from the Supreme Court's 1983 opinion refusing to exclude psychiatric testimony in a capital sentencing proceeding labeled unreliable by the American Psychiatric Association: "Petitioner's entire argument . . . is founded on the premise that a jury will not be able to separate the wheat from the chaff. We do not share in this low evaluation of the adversary process" (Barefoot v. Estelle, 463 U.S. 880, 901 n.7 [1983]). (As we shall see below, one of the critical differences in the gatekeeper model is its rejection of this faith in the abilities of juries.) Experts are expected to play a useful, partisan role in the adversarial model, as reflected in another Supreme Court opinion recognizing the defendant's constitutional right to the appointment of a psychiatrist to assist his attorney in the presentation of an insanity defense. "Without the assistance of a psychiatrist to conduct a professional examination on issues relevant to the defense, to help determine whether the insanity defense is viable, to present testimony, and to assist in preparing the cross-examination of a State's psychiatric witnesses, the risk of an inaccurate resolution of sanity issues is extremely high. With such assistance, the defendant is fairly able to present at least enough information to the jury, in a meaningful manner, as to permit it to make a sensible determination" (Ake v. Oklahoma, 470 U.S. 68, 82 [1985]).
The traditional adversarial model has relied heavily on the jury to decide the ultimate issues in the case. It zealously guarded the jury's prerogative by excluding expert testimony when the issues were not "beyond the ken" of the jury or when the expert testimony threatened to usurp the function of the jury, criteria that have been relaxed in recent years. When expert testimony is admissible on an issue, the requirements for admissibility under the traditional adversary approach focus predominantly on the qualifications of the expert, leaving scrutiny of the validity of the expert's methods and procedures to the fact finder as part of its assessment of the appropriate weight to be accorded the evidence in reaching a decision on the ultimate issues. The standard applied in assessing qualifications is a functional determination to which the trial judge is accorded significant discretion. So, in assessing the qualifications of a physician to testify as an expert, the standard typical of the adversarial approach notes:
An expert need not have certificates of training, nor memberships in professional organizations. . . . Nor need he be . . . an outstanding practitioner in the field in which he professes expertise. Comparisons between his professional stature and the stature of witnesses for an opposing party may be made by the jury. . . . the only question for the trial judge who must decide whether or not to allow the jury to consider a proffered expert's opinions is, "whether his knowledge of the subject matter is such that his opinion will most likely assist the trier of fact in arriving at the truth." (United States v. Barker, 553 F.2d 1013, 1024 [6th Cir. 1977])
Under the traditional adversarial model, once having determined that the expert is qualified, it is rare for the court to engage in a searching analysis of the expert's expertise in determining admissibility (Eymard v. Pan American World Airways, 795 F.2d 1230 [5th Cir. 1986]). Only when the expert has sought to present novel sources of expertise, purportedly grounded in science, have courts applied more rigorous threshold scrutiny as a prerequisite to admissibility (Frye v. United States, 293 F. 1013 [D.C. Cir. 1923]). Articulating the approach that characterizes the traditional adversarial model, the Supreme Court noted that "the rules of evidence generally extant at the federal and state levels anticipate that relevant, unprivileged evidence should be admitted and its weight left to the factfinder, who would have the benefit of cross-examination and contrary evidence by the opposing party" (Barefoot v. Estelle, 463 U.S. at 898). Under this approach, medical expert testimony in medical malpractice or personal injury cases has rarely invoked threshold scrutiny beyond determining the witness's qualifications, the basis for the opinion, or the confidence with which it was expressed (Black 1988).
Although clinical practice guidelines and science-based medical evidence are not synonymous, clinical practice guidelines are the most common manifestation of science-based medical evidence with which courts have dealt. The absence of reported decisions addressing the admissibility of practice guidelines suggests that lawyers and judges have assessed expert testimony offering science-based medical evidence from the perspective of the traditional adversarial model. Although practice guidelines play an active role in medical malpractice litigation (Hyams, Shapiro, and Brennan 1996), the reported decisions reflect that lawyers and judges have not regarded the guideline's validity as an expert or scientific evidence admissibility issue. "Without much fanfare, litigants have introduced and courts have approved the use of practice guidelines to provide evidence of the relevant standard of care" (Shuman 1997a: 104).
In a negligence action, in the absence of an analysis of negligence in which a statute or regulation defines the standard of care (e.g., exceeding the posted speed limit), the jury is charged with determining what society is entitled to expect of an actor under the circumstances (i.e., the behavior of the proverbial reasonable person). From the perspective of the adversary model, whether guidelines are "quality enhancing" or "cost-reducing" (Brennan 1991), they may provide the fact finder with important information about customary practice, the practice of a respectable minority, reasonable prudence, or acceptable practice, to consider in its determination of reasonableness under the circumstances (Rosoff 1995; Havighurst 1991).
Legislatures and courts have yet to determine how triers-of-fact should use practice guidelines. They can be extremely helpful in cases calling into question whether a physician chose the wrong course of diagnosis or treatment or should have gone further in attempting to understand or correct the situation. . . . However, they should not necessarily be viewed as conclusive evidence of the standard of care. Proof of compliance with practice guidelines should not necessarily establish due care; just as proof of noncompliance should not establish negligence per se. Clinical practice guidelines can materially assist the triers-of-fact in medical malpractice cases. Properly authenticated clinical practice guidelines are relevant to the question of the proper standard of care and should be admitted as substantive evidence if introduced through a witness who can lay a proper foundation. (Frakes v. Cardiology Consultants, No. 01-A-01-9702-CV-0069, 1997 Tenn. App. LEXIS 597, at *15-16 [Tenn. App. Aug. 29, 1997])1
Courts relying on the adversarial model have not engaged in demanding scrutiny of the admissibility of science-based medical evidence. Rather, they have regarded it as important feature of the adversary model to provide all such relevant information to the jury, who, with the benefit of competent counsel's rigorous cross-examination and presentation of opposing expert evidence, can assess the reliability of this evidence and give it the appropriate weight in their determination.
The gatekeeping approach to the admission of expert testimony rests on the belief that the traditional adversary model has not worked well in scrutinizing expert testimony. Its critique of the operation of the traditional adversary model is that many judges have been unwilling or unable to exclude unreliable claims of expertise (Angell 1996); that there are large numbers of experts willing to offer testimony that would not satisfy the standards for work in their profession's laboratories, clinics, or journals;2 that attorneys operating under the ethos of the adversary system have sought experts to support their case without regard to their professional competence;3 that jurors lacking scientific or technical expertise have relied on irrational, superficial criteria to assess the believability of experts;4 and, accordingly, heightened scrutiny of the admissibility of expert testimony is necessary (Huber 1991).
In contrast with the traditional adversarial approach, the gatekeeping approach assumes that it is appropriate for the judge to impose a demanding standard of scrutiny for the admissibility of expert testimony, and given doubts about the abilities of juries that characterize the gatekeeping model, the role of the jury in assessing the reliability of expert testimony is more circumscribed. Similarly, the gatekeeping approach assumes that the role of lawyers in trying cases, and the role of experts in presenting evidence, will be more circumscribed than under the traditional adversarial model.
Although the gatekeeper model calls for raising the threshold for admitting expert testimony, those calls have been directed at standards for assessing the reliability of the expert's methods and procedures, not the expert's qualifications. Even in courts that have embraced the gatekeeper model, the standard for scrutiny of the expert's qualifications is unchanged from the traditional adversary model. It remains a functional analysis of the expert's ability to provide relevant evidence on the issue for which the expert is offered. "What is required is that the offering party establish that the expert has 'knowledge, skill, experience, training, or education' regarding the specific issue before the court which would qualify the expert to give an opinion on that particular subject" (Broders v. Heise, 924 S.W.2d 148, 153 [Tex. 1996]).
One barrier that stands in the way of changing this approach for the scrutiny of medical experts' qualifications is the absence of relevant, comprehensive, and authoritative credentialing criteria. Where would courts turn for guidance? There are no federal or state rules or regulations enumerating an exhaustive list of medical procedures and the qualifications required to perform them, let alone privately promulgated guidelines. And the standard of review continues to leave the issue to the discretion of the trial court.5
The gatekeeper model articulated in the Supreme Court's recent trilogy on the admissibility of expert testimony under the Federal Rules of Evidence-Daubert v. Merrell Dow Pharmaceuticals (509 U.S. 579 [1993]), General Electric Co. v. Joiner (522 U.S. 136 [1997]), and Kumho Tire Co. v. Carmichael (526 U.S. 137 [1999])-places on the trial court judge "the task of ensuring that an expert's testimony rests on a reliable foundation and is relevant to the task at hand" (Daubert, 509 U.S. at 597). Rejecting the federal rules' incorporation of the Frye "general acceptance"6 test that relied on consensus to assess the admissibility of novel scientific evidence, the Daubert Court constructed a standard built on the work of Karl Popper (1989; see also Susan Haack in this issue), which relies on falsifiability as the hallmark of the scientific enterprise, considering:
Joiner clarified that appellate courts reviewing trial court decisions under Daubert are to reverse only when the trial court abused its discretion (i.e., failed to use sound legal reasoning), a standard that has traditionally granted wide latitude to the decisions of the trial court. And Kumho Tire clarified that the Daubert criteria applied to all proposed expert testimony, whether grounded in scientific, technical, or other specialized knowledge, but "whether Daubert's specific factors are, or are not, reasonable measures of reliability in a particular case is a matter that the law grants the trial judge broad latitude to determine" (Kumho Tire, 526 U.S. at 153).
The Daubert, Joiner, Kumho Tire trilogy has important implications for science-based medical evidence. If judges are required to act as gatekeepers so that juries hear only relevant and reliable expert testimony, then only expertise derived from asking "What's the evidence" (Eisenberg 1999: 1869) should satisfy the admissibility threshold for claims of medical expertise. If it is not acceptable to admit an expert's conclusion, "just because somebody with a diploma says it is so" (United States v. Ingham, 42 M.J. 218, 226 [A.C.M.R. 1995]), then asking about testability, peer review and publication, error rates, and acceptance within the relevant scientific community of the expert's methods and procedures are sensible requisites for claims of medical expertise in the courts as well as in medical practice. How various practice guidelines would fare under that analysis, let alone what currently accepted claims of medical expertise meet that threshold, would present an interesting study.