Expert Psychological Testimony in Rape Trials: A Social-Cognitive Analysis

In three studies with undergraduate subjects, we investigated juror use of group probability data (base rates) in the form of expert scientific testimony in a simulated rape trial. In Study 1 we hypothesized that juror use of such evidence would be influenced by the type and timing of the expert testimony presented. As predicted, jurors made the most use of the expert testimony when it was linked explicitly to the case under consideration and presented early in the trial. Study 2 demonstrated that the observed effects were not attributable to differences in the duration of the expert testimony or to enhanced recall and suggested that use is facilitated by concrete rather than abstract presentations of expert testimony. In Study 3 juror use of expert testimony was further examined by analyzing jury deliberations from Study 1. Results show that although juries hardly discussed the expert testimony itself, the expert testimony influenced interpretations of case facts.