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by J. Scott Janoe, John D. Daley and Thomas F. Allen, Jr. - Harvard Law School '99
Expert witnesses have become fixtures in today's courts. From fiber comparisons to economic projections and psychiatric evaluations, the range of offered expertise covers the span of human knowledge. Hardly a case of any consequence goes to trial without expert witnesses of some kind.
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 be 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 that "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 lay 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 are to decide for themselves whether an expert's methodology -- the often highly complicated basis for the conclusions -- is 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. Louisiana, for example, adopted a variant of the Daubert test in State v. Foret.(9) While few state 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 roadmap for the expansive gatekeeping terrain, the remainder of this introduction outlines the history of judicial gatekeeping in Louisiana, and a synopsis of the more detailed discussions to follow.
Gatekeeping in Louisiana
1) the subject of the inference must be so distinctly related to some science, profession, business or occupation as to be beyond the under-standing of the average layman; and 2) the witness must have sufficient skill, knowledge or experience in that field or calling as to make it appear that his opinion or inference will probably aid the trier of fact in his search for truth.(11)Justice Dennis also included other variables to be considered in making admissibility determinations including: a preference for direct, concrete evidence over inferential evidence along with the purpose of the evidence and how close it was to the "hub" of the trial.(12) As Louisiana had rejected the Frye test in State v. Cantanese(13) three years earlier, the Wheeler analysis remained the primary means of evaluating admissibility of expert testimony until the adoption of the Code of Evidence.(14)
Soon after Louisiana adopted the Code of Evidence, state courts began to rely upon its provisions to develop standards for admissibility. To this end, the Louisiana Courts of Appeal for the second, third, and fourth circuits adopted the standards articulated by the United States Court of Appeals for the Fifth Circuit in Christophersen v. Allied-Signal Corp.(15) The Christophersen analysis consisted of four inquiries, with the first three serving as threshold requirements:
(1) [w]hether the witness is qualified to express an expert opinion, Fed. R. Evid. 702; (2) whether the facts upon which the expert relies are the same type as are relied upon by other experts in the field, Fed. R. Evid. 703; (3) whether in reaching his conclusion the expert used a well-founded methodology, Frye; and (4) assuming the expert's testimony has passed Rules 702 and 703 and the Frye test, whether under Fed. R. Evid. 403 the testimony's potential for unfair prejudice substantially outweighs its probative value.(16)Although the adoption of the Code of Evidence and the growing acceptance of the Christophersen analysis helped bring relative uniformity to judicial practice in regards to admissibility of experts in Louisiana, there remained uncertainty as to what the proper standards for admissibility should be. In State v. Foret the Supreme Court of Louisiana helped clear up this confusion.
State v. Foret: "The Reliability
Threshold and Relevance"
The Daubert "observations" serve as a sort of checklist for reliability. They include such factors as:
1. the "testability" of the expert's theory or technique;These Daubert factors are not, however, to be taken as a rigid, uncompromising test. Failure to satisfy one or more of the requirements does not automatically make testimony inadmissable. The trier of fact is the ultimate arbiter of admissibility and remains empowered to exercise discretion to admit expert testimony it believes is both reliable and relevant.(22)
As previously alluded to, the reliability inquiry is coupled with the article/Rule 702 relevance requirement that the expert's testimony must assist the trier of fact in understanding or determining a fact in issue. Ultimately, Daubert, and by extension Foret, created a two-pronged test requiring the trial judge to make a preliminary assessment, preferably outside of the jury's presence, that the expert is proposing to testify to actual scientific knowledge (the reliability prong) and that such knowledge will assist the trier of fact (the relevance prong).(23) Testimony must meet both of these standards in order to be admissible under Foret. Finally, the Foret court recognized that Daubert-type analysis requires the court to employ the balancing test of Federal Rule of Evidence 403(24) to determine if the probative value of given evidence is outweighed by its potential for unfair prejudice.(25)
Since Foret Louisiana courts have employed the Daubert standards in a variety of civil and criminal cases.(26) The standard of review used for trial courts' decisions on admissibility in Louisiana has been abuse of discretion. This strict standard has been interpreted to require a showing that the trial judge's decision to admit or disallow evidence was manifestly erroneous and more than harmless error to warrant overruling of a lower court's decision(27) In addition, the state courts of appeals have demonstrated an unwillingness to engage in sua sponte examination of proffered expert testimony requiring counsel to put forward admissibility challenges themselves at the trial level.(28)
Joiner and the Future
of Judicial Gatekeeping [Click here
for the Joiner update.]
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 on the distinction between fact and law. One way to view Daubert gatekeeping is as 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 options?
11. Judges are not scientists 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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