This study empirically and statistically analyzed jurors' evaluation and utilization of expert psychiatric testimony in trials involving an insanity defense. The subjects were thirty-four jurors who served in live jury trials in three counties in northern California. Jurors' evaluation and utilization of psychiatric testimony was assessed by a three-part questionnaire: (1) an open-ended questionnaire procedure conducted with each juror in an interview with the researcher; (2) a self-administered form for each juror to rank order components of the trial with the set to indicate the degree of importance they attached to each in reaching their verdicts; and (3) a seventy-two item self-administered questionnaire to evoke jurors' ratings of expert witnesses' characteristics and courtroom behavior. Nonparametric statistical procedures were utilized throughout the study. Although no definitive conclusions can be drawn concerning the role psychiatric testimony plays in jurors' reaching their verdicts, certain trends emerge which warrant and stimulate future investigation.