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Evidence Matters: Science, Proof, and Truth in the Law, Susan Haack. Cambridge: Cambridge University Press, 2014, 446 pages, $34.99 paperback.
Expert testimony has troubled judges for centuries. Since judges rarely have backgrounds in science, having to tell genuine knowledge from hokum is frequently a challenge, especially in this era of increasing courtroom use of expert testimony. In this book of "interdisciplinary essays," Susan Haack, renowned epistemologist, attempts to teach judges something about how to evaluate scientific testimony by focusing on the intersection of law, philosophy, and science, invoking concepts of inquiry and truth as they are used in all three disciplines.
The reason it is up to judges to decide whether expert testimony is genuine knowledge that would be helpful to the jury is the Supreme Court's Daubert decision,1 which placed the gatekeeping task of evaluating scientific validity on federal judges. The Court's subsequent decisions elucidated the gatekeeping requirement;2 and the amendment to Federal Rule of Evidence 702 codifies these decisions.3
Based on the judge's duty to assess relevance in determining admissibility, the Daubert Court told federal judges to engage in a "preliminary assessment of whether the reasoning or methodology underlying the testimony is scientifically valid and whether that reasoning or methodology properly can be applied to the facts in issue."4 The rationale for permitting experts - who have no personal knowledge of the events at issue - to testify, the Court noted, "is premised on an assumption that the expert's opinion will have a reliable basis in the knowledge and experience of his discipline."5 The Court then gave judges some "general observations" (the Daubert factors) to guide their assessment: testability,6 subjection to peer review and publication,7 known or potential error rate and the existence and maintenance of standards,8 and general acceptance.9
Daubert linked the idea of reliability to helpfulness: something cannot be helpful to the jury if it is not reliable - meaning trustworthy. Rule 702 as amended tries to give guidance to the trustworthiness inquiry. It provides that a qualified witness may testify if it would be helpful to the trier of fact (usually the jury), and "the testimony is based on sufficient facts or data . . . is a product of reliable principles and methods . . . reliably applied...