Impoverishing the Trier of Fact: Excluding the Proponent's Expert Testimony Due to the Opponent's Inability to Afford Rebuttal Evidence

38 Pages Posted: 24 Apr 2007

See all articles by Edward J. Imwinkelried

Edward J. Imwinkelried

University of California, Davis - School of Law


There is a marked tendency toward the expanded use of expert testimony at trial. However, such testimony can be expensive. A 15 second computer generated animation (CGA) can cost $20,000, and likewise DNA testimony can be quite costly. Thus, the increased use of expert evidence places poorer litigants at a distinct disadvantage.

One way to level the evidentiary playing field is to provide the poor litigant with expert services. Under Ake v. Oklahoma, 470 U.S. 68 (1985), the Constitution sometimes compels the appointment of an expert for an indigent accused. An appointment for an indigent accused is also possible under the Criminal Justice Act. However, in practice, such appointments are few and far between.

Another way to level the playing field is to exclude the wealthier proponent's expert testimony. In a 2006 decision, Commonwealth v. Serge, 586 Pa. 671, 896 A.2d 2006 (2006), in dictum several members of the Pennsylvania Supreme Court expressed the view that when the opponent cannot afford rebuttal testimony, that state's Rule 403 sometimes authorizes the trial judge to bar the proponent's testimony. Pennsylvania's Rule 403 is identical to Federal Rule of Evidence 403; and in a survey mentioned in the article, a number of federal District Court judges expressed the same view.

The purpose of this article is to analyze the propriety of using Rule 403 in that fashion. On the one hand, the article concludes that Rule 403 does not embody any egalitarian objective. Rule 403 does not authorize the judge to exclude the proponent's testimony simply because the jury is likely to find the testimony impressive and the opponent cannot afford to hire a rebuttal witness.

On the other hand, the article argues that on occasion, there is a justification for barring the proponent's testimony under Rule 403. Rule 403 tasks the trial judge to balance the probative value of the evidence against its incidental probative dangers. One of those dangers is the risk that the jury will attach excessive weight to the testimony. The article contends that that risk is acute when three factors concur: The proponent's expert has impressive credentials, the expert's analytic technique does not include an objective decisional rule, and there are no data as to the error rate for the technique. To be sure, in many cases, the trial judge has other tools - the invocation of the learned treatise hearsay exception, judicial notice, and cautionary instructions - to minimize the risk. However, in an extreme case when the three factors concur and these tools are unavailable to the judge, the drastic step of exclusion under Rule 403 is warranted.

Suggested Citation

Imwinkelried, Edward J., Impoverishing the Trier of Fact: Excluding the Proponent's Expert Testimony Due to the Opponent's Inability to Afford Rebuttal Evidence. Connecticut Law Review, Forthcoming, UC Davis Legal Studies Research Paper No. 104, Available at SSRN:

Edward J. Imwinkelried (Contact Author)

University of California, Davis - School of Law ( email )

Martin Luther King, Jr. Hall
Davis, CA CA 95616-5201
United States

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