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3 The Legal Landscape Post-Daubert These three Supreme Court decisions have led to increasing attention on the part of judges to scientific and technical issues (Berger, 2000). For instance, the Federal Judicial Center has published two editions of the Reference Manual on Scientific Evidence that contain a number of chapters on topics such as epidemiology, toxicology, and statistics that are highly relevant to determining causation in toxic tort cases. In addition, numerous training programs have been held for judges and lawyers on issues relating to scientific proof. Despite this educational effort, difficult issues remain. The Daubert criteria are too general to resolve many of the difficult problems facing the courts when complex scientific evidence is presented to prove causation. The factors discussed by the Supreme Court do not necessarily help the courts evaluate the consistency of expert judgment, determine when it is reasonable to extrapolate from other studies, determine whether the methodology used in one study is comparable to that used in another, or assess how conflicting standards and methodologies across varying areas of science should be considered. Nor does the Court provide guidance when scientific evidence is suggestive about where to draw the line between reasonable inference (which is permitted) and speculation (which is not permitted). Moreover, there are some areas of science that are so new and so complex that deciding what evidence is admissible and what testimony should be heard remains a formidable challenge. There is some evidence that application of the Daubert standards has in fact restricted the presentation of expert evidence, 7

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DISCUSSIONS OF THE COMMITTEE ON DAUBERT STANDARDS as indicated by increased exclusions of expert testimony in federal courts (Dixon and Gill, 2001). A 2001 study by the Rand Institute for Civil Justice found that judges are acting as gatekeepers for reliability and relevance; they are examining the methods and reasoning underlying the evidence; and they appear to be using general acceptance as only one of many factors that can enter into a reliability assessment. A 1998 survey of judges found that a third claimed to admit expert evidence less often than they did before Daubert and well over half of the attorneys surveyed reported the same trend in judges' rulings (Krafka et al., 2002). Many view this as demonstrating improvement in the quality of scientific evidence presented in the courtroom. They see the data as showing that the courts are complying with the obliga- tion established by Daubert and its progeny to act as gatekeepers to ensure the integrity of scientific evidence. Some claim that judges have continued to admit scientific evidence that properly should have been excluded. But others have argued that the application of these standards has been inconsistent with accepted scientific practice in certain cases, and that judges have been too aggressive in excluding evidence. For example, some judges tend to assess scientific testimony by examining each item of supporting evidence in isolation rather than examining the cumulative weight of the evidence in the manner in which the scientific community reaches a consensus of opinion. Moreover, many judges have expressed a preference for some forms of scientific evidence over other types (e.g., epidemiology may be preferred over toxicology in toxic tort cases) without an assessment of the relative strength or statistical power of the study designs. Judges also may be hesitant to general- ize from specific research findings to conclusions, following the warning of Chief Justice Rehnquist to beware of testimony that is based on "too great an analytical gap between the data and the opinion proffered" (General Electric v. Joiner, 1997). The diversity of views within science on the nature of 8

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The Legal Landscape Post-Daubert causation1 and the methodology needed to make claims about causation has complicated the efforts of the courts to identify credible views that should be presented to a jury. Judges have sometimes excluded testimony that some within the scientific community might consider relevant, reliable, yet still somewhat uncertain, and at times have allowed testimony that scientists might view as unreliable or irrelevant. The role of uncertainty in the culture of science is a particularly complex question, not always easily grasped in the legal arena. Judges often must review testimony from several different scientific disciplines. In toxic tort cases, for example, the evidence pertaining to causation could involve laboratory studies from toxicology and molecular biology, clinical studies (including randomized trials), observation, epidemiological studies of various designs, and case studies. Depending on the state of the science, some or no information might be available from each of these disciplinary areas. Compounding this complexity is another issue: for any given case, there may be published reviews of these same scientific studies, providing the court with analysis and synthesis of the evidence, and often an assessment of the likelihood of causa- tion. There are, then, two major categories of scientific evidence available to the courts: individual analytic studies and summary syntheses of bodies of evidence; both categories may be peer- reviewed but they involve quite different methodologies. Several concerns have been raised about the courts han- dling of scientific evidence and expertise, in particular: Whether decisions are being made consistently. Whether there is sufficient recognition of minority views in science. 1 For a discussion of these different viewpoints, see M. Parascandola and D.L. Weed. Causation in epidemiology. Journal of Epidemiology and Community Health 55:905-912, 2001. 9

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DISCUSSIONS OF THE COMMITTEE ON DAUBERT STANDARDS Whether courts appreciate differences among the sciences in collecting, validating, and synthesizing evidence. Whether courts appreciate that much of the available research relates to populations rather than to individuals and that complex questions may arise in extrapolating data to a particular person. Whether the Supreme Court's comprehension of the concept of validity corresponds with the scientific community's understanding of the term. Whether forensic evidence in criminal cases is receiving an appropriate level of scrutiny; Whether judges, by excluding too much evidence, are intruding on the constitutional role of the jury to resolve disputed facts. 10