Expert Witnesses, Adversarial Bias, and the (Partial) Failure of the Daubert Revolution
- Author(s): David Bernstein
- Date Posted: 2007
- Law & Economics #: 07-11
This manuscript raises two questions that have been surprisingly missing from the voluminous law review literature on expert evidence since the landmark Daubert decision. First, what is the underlying rationale for the replacement of the old qualifications-only, let-it-all standard for expert testimony with Daubert/Federal Rule of Evidence 702's requirement that all expert testimony be subject to a stringent reliability test? Second, once we have identified this rationale, has the "Daubert revolution" succeeded on its own terms?
I conclude that the implicit rationale for the reliability test is to preserve the perceived advantages of the adversarial system, while mitigating the harms to the courts' truth-seeking function by the inevitable strong biases that accompany adversarial expert testimony. These biases include the conscious biases of hired guns, the unconscious biases of other paid experts, and the selection biases that result from the fact that attorneys "shop" for their experts from a large pool of qualified individuals.
Rule 702 thus attempts to serve a worthy goal, but it far from fully succeeds in efficiently achieving this goal. First, in the context of forensic expertise in criminal cases, Rule 702 does nothing to address the huge gaps in resources between the prosecution and most defendants that severely inhibit defendants' ability to challenge unreliable prosecution expert testimony.
Second, Rule 702, applied correctly, does succeed in barring "junk science" causation evidence in toxic torts cases. However, it does so at the expense of excluding speculative evidence supporting causation, even when most experts in the field would conclude that the relevant evidence is a sufficient basis from which to find causation by a preponderance of the evidence. While Rule 702 is easily preferable to the prior overly permissive regime, it likely goes too far in insisting on a reliability test that makes the courtroom stricter about causation evidence than is the scientific community itself. The way around this problem is to amend Rule 702 to allow courts to admit educated guesses about causation, but only when nonpartisan experts, not subject to adversarial bias, are willing to make such guesses.
Finally, Rule 702 puts severe restrictions on the testimony of experience-based testimony by connoisseurs. Such experts may only testify if their field of expertise is a legitimate one, and they have proven to the court that they truly have the expertise they claim. Rule 702 also properly prevents attorneys from shopping for outlier and hired gun connoisseurs, given that there is no objective way for a jury to determine whether an experience-based expert's views are correct or representative of other experts in the field. Therefore, in the context of connoisseur testimony, courts should either replace adversarial experts with a panel of nonpartisan experts, or only allow an adversarial expert to testify if his conclusions are consistent with those of a nonpartisan advisory panel.