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by Christopher T. Newkirk and Thomas F. Allen, Jr. - Harvard Law School '99
[Presented in the Spring of 1997 at the Judicial Gatekeeping Seminar in Alabama.]
What is the trial judge's role in overseeing the testimony of expert witnesses? Unlike lay witnesses, whose testimony a jury can evaluate with common sense and experience, expert witnesses offer conclusions based on practices and knowledge beyond the ken of the average juror. As a consequence, testimony by unpoliced expert witnesses can have a potentially prejudicial effect on jurors, who may be inclined to believe the experts based solely on their status as such. How is the trial judge to know whether the expert is merely speculating, or whether the evidence on which the expert bases his or her testimony is sufficient to support the conclusion? Judges certainly prevent lay witnesses from speculating and are expected to exclude a witness offering wholly speculative testimony. Why should the situation differ when the witness purports to be an "expert"?
If one accepts the proposition that the trial judge has a duty to exclude unreliable experts, a host of concerns inevitably follows. How is a trial judge to assess the scientific or technical adequacy of expert testimony if even a cursory understanding of the issues requires specialized training? Can anyone without such training fully understand the issues and come to a rational conclusion as to their validity? To what degree can the trial judge rely on the expert's own assertions about his or her qualifications? All of these concerns carry heavy weight for in many cases the trial judge is hardly a more qualified assessor of scientific credibility than the jury itself.
For more than half a century, American courts relied on the scientific community for assistance in their gatekeeping endeavor. In Frye v. United States, the Court of Appeals for the District of Columbia held that in order to be admissible, the basis for expert testimony must be "sufficiently established to have gained general acceptance in the particular field in which it belongs."(1) This became the standard in federal and most state courts for seventy years. The reasoning was simple: science was to be left to the scientists. The Frye test ensured that "those most qualified to assess the general validity of a scientific method will have the determinative voice."(2)
Yet oftentimes the "general acceptance" test seemed to have been in tension with changes in federal trial procedures. The Federal Rules of Evidence (FRE), passed in 1975, adopted a "liberal" approach for federal courts. Rule 402 states, "All relevant evidence is admissible," and Rule 702 calls for admissibility of expert testimony "[i]f scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue." After the promulgation of the FRE many began to question whether the Frye test was in tune with the prevailing law. The major criticism of Frye was that novel, yet otherwise completely reliable evidence was often excluded because scientists had not yet "accepted" its validity. Aggrieved parties were forced to lie in wait, as the scientific community meticulously examined the details of an otherwise "logically reliable" method.(3)
The Supreme Court sought to remedy this problem in 1993. In Daubert v. Merrell Dow Pharmaceuticals, the Court held that the FRE superseded the Frye test.(4) The Court held that the essential concerns of the Rules, and of Rule 702 in particular, were reliability and relevancy. While Frye was designed to flush out unreliable testimony, its test was not determinative and did not preclude further analysis. The Court held that when faced with expert witness testimony, the trial judge has a responsibility to determine "whether the expert is proposing to testify to (1) scientific knowledge that (2) will assist the trier of fact to understand or determine a fact in issue."(5)
The Court went on to hold that this "gatekeeping" role requires the trial judge to make a "preliminary assessment of whether the reasoning or methodology underlying the testimony is scientifically valid, i.e., whether it is reliable."(6) Furthermore, the evidence must be "relevant to the issue involved."(7) In order for expert testimony to be admissible, both prongs of the test must be met. Finally , the Court cautioned the judge to be sure that the inquiry only attacks the reliability of the underlying methods, and not the correctness of the expert's final conclusion--a determination that is reserved for the jury.(8)
Suddenly, the Federal judge could no longer rely on the scientific community for a determination of an expert's credibility. Instead, judges are to make the determination on their own. Federal trial judges were forced to decide for themselves whether an expert's methodology--the often highly complicated basis for the conclusions--was reliable.
Although the Daubert case itself deals only with trials conducted under the Federal Rules of Evidence, most states have chosen to adopt its test in one form or another. At this moment, Alabama courts generally follow a modified Frye test, but a statutory exception in which the legislature has mandated that the Daubert standard be followed suggests that this area of law is in flux in Alabama. While few states trial judges will ever hear a mass toxic tort case such as Daubert, this does not diminish the need to understand the Daubert rulings for questions of admissibility arise in a variety of civil and criminal cases. Much like the evidence offered, the judicial mechanisms for dealing with a Daubert challenge are still in the frontier stage. Attorneys will develop new means of both offering and challenging expert testimony, and the trial judge must be prepared to deal with them.
It is the intent of this paper and those that follow to explore the many questions surrounding the judge's gatekeeping role. Acting as a road map for the expansive gatekeeping terrain, the remainder of this introduction outlines the state of judicial gatekeeping in Alabama and introduces the specific gatekeeping issues discussed in more detail in the following papers.
Ex parte Perry: A Modified
1. Is there a theory, generally accepted in the scientific community, that supports the conclusion that DNA forensic testing can produce reliable results?The first two questions are clearly in line with Frye, requiring "general acceptance" of the theory and techniques supporting the evidence. The third question requires a more invasive judicial gatekeeping inquiry than previously called for--a precursor to the kind of role Daubert now requires federal judges to play. While noting that Perry never requested a hearing outside the presence of the jury to challenge the admissibility of the DNA matching evidence and the DNA population frequency statistics used to convict him, the Court nonetheless remanded the case to the trial court for an evidentiary hearing evaluating the evidence in light of the newly promulgated three-pronged test.(13) This is just the sort of hearing that Daubert now requires in federal court, though the standard for admissibility obviously differs.
The Alabama DNA Database System
Statute: The Legislature Adopts Daubert
genetic identification technology through DNA testing is generally accepted by the relevant scientific community . . . [and] is capable of producing reliable results . . . [and] should be admissible as a matter of evidence . . . and that juries . . . should be responsible for assessing the weight, if any, to be given to expert testimony or evidence.(15)
This assault on the Perry Court's skepticism regarding the use of DNA evidence reaches its apex in the section of the statute concerning expert testimony. Section 36-18-30 states that expert DNA testimony and evidence "shall be admissible and accepted as evidence. . . provided . . . the trial court shall be satisfied that [it] meets the criteria for admissibility as set forth. . . in Daubert." Though the legislation is silent on Perry, the DNA Database System statute changes the admissibility standard applicable for DNA evidence and seems to abolish Perry, at least for the purpose for which Perry was decided.(16) Perhaps Perry's modified Frye test remains the standard in non-DNA cases; in that case, the Alabama trial judge must know how to apply whichever test is appropriate.
Perry held that the test for admissibility of novel DNA evidence was a modified Frye test. The legislature changed the law on this narrow question and declared Daubert the standard for admissibility of DNA evidence. Yet the most recent authority to speak on the general question of what standard a judge should apply to determine admissibility of expert testimony and evidence, the Advisory Committee on the Rules of Evidence, stated that Frye remained the standard in Alabama and cited Perry in support of this proposition. It is, then, arguably an open question what standard the Alabama Supreme Court would apply today to the determine the admissibility of expert, scientific testimony.
The Breast Implant Multidistrict
Pretrial Discovery: The Northern District of Alabama at the Focus of Nationwide
Issues Presented In This Volume
1. How has the role of judicial gatekeeping evolved in the United States? How has the balance of power between judge and jury shifted in reaction to trends in American history?
2. What is the influence of summary judgment on the development of judicial gatekeeping? Gatekeeping clearly is rooted in the traditional division of responsibilities between judge and jury and in the distinction between fact and law. One way to view Daubert gatekeeping is an another means by which the judge may assert his role as arbiter of questions of law. In a practical sense, what is the relationship between admissibility decisions and motions for summary judgment?
3. What is the scope of a gatekeeping judge's admissibility determination in regard to assessing the reliability of expert testimony? How is Daubert a change from the Frye test?
4. How is a judge to determine whether expert testimony is reliable and relevant? Daubert dictates that a judge review the methodology but not the conclusions of an expert. This distinction is stickier than it appears at first glance. How does the methodology-conclusion debate impact a judge's admissibility determination? How do judges meet the Daubert command to exclude unreliable evidence without attempting to decide what constitutes "good science"?
5. Does Daubert apply to areas other than new science? Is science a special case? Or does Daubert-type gatekeeping also apply to experts in such fields as economics and psychiatry? If so, might the judge's evaluation of social science methodology differ from that of a "hard" science like biology or chemistry?
6. In toxic tort cases such as Daubert, plaintiffs attempt to establish causation through the use of epidemiological studies, which endeavor to measure a statistical relationship between exposure to an agent and the incidence of a harmful condition. Are such studies necessary to prove causation? Are they helpful? How should testimony relying on epidemiological evidence be treated?
7. Questions of admissibility can be quite complex when dealing with the testimony of an expert based on his "expertise" and experience in a given field. Physicians often present testimony to courts, and judges must decide whether or not it is admissible. How should a judge evaluate a physician's testimony based on differential ("clinical") diagnosis?
8. What are the procedural issues surrounding judicial gatekeeping? Practically speaking, how is the judge to accomplish his or her task?
9. Can Daubert hearings be given precedential value? Should one judge's assessment of certain scientific evidence command that other judges follow the same path? Or can the issue of adequacy of an expert's testimony be repeatedly litigated? How much should judges worry about conflicting court decisions on the validity of certain types of methodology?
10. What is the standard for appellate review of a Daubert hearing? Should a trial judge's evidentiary determination be subject to the traditional discretionary standard? Or should de novo review be applied so as to create more consistent treatment of scientific evidence? The current split in federal courts surrounding this issue will be decided next term in the Joiner case. What are the policy implications of the Court's opinions?
11. Judges are not scientist nor statisticians, yet they are asked to
make admissibility rulings on expert opinions that are often grounded in
statistical studies. How much weight should judges lend to statistical
measures of scientific proof? More specifically, how important are "significance
levels" and "confidence intervals" in determining the reliability of a
certain study? Nowhere is the uneasy interface between science and legal
evidence more apparent.
F. 1013, 1047 (D.C. Cir. 1923).
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