, Volume 15, Issue 5, pp 495-507

Barring ultimate issue testimony

Abstract

This research focuses on one of the major changes wrought by the Insanity Defense Reform Act of 1984: the exclusion of expert mental health testimony on the “ultimate issue,” that is, testimony specifically addressing the expert's opinion that the defendant is sane or insane. Subjects in this research were presented with 1 of 10 variants of an insanity case in which experts testified for the defense, prosecution, both, or neither. The testimony was at one of three levels: diagnostic only, penultimate issue, or ultimate issue. Results showed that level of testimony had no effect on the verdict pattern. There was evidence to suggest that this effect may occur because jurors infer, and/or mistakenly recall, higher levels of expert testimony than was actually presented to them. In addition, general and specific constructs (Finkel & Handel, 1989) that predict verdict yieldedR 2 values from .500 to .668 and were not significantly affected by the level of expert testimony. Implications of these findings are discussed.

A version of this paper was presented at the annual convention of the American Psychological Association, August, 1990, Boston, MA.