Juror decision-making in a mock sexually violent predator trial: gender differences in the impact of divergent types of expert testimony.

Despite widespread use of mental health testimony in cases where violence risk is at issue, relatively little is known about the impact of such information on juror decision-making. This study addressed the effects of testimony based on three types of risk assessment instrument or method (clinical opinion, actuarial assessment, and ratings of psychopathy) to examine whether they would have differential impact on jurors' perceptions of the defendant. In a mock sexually violent predator civil commitment trial, 172 undergraduates were presented a case summary that included prosecution and defense expert testimony related to violence risk based on one of the three methods noted above. Consistent with earlier research, the hypothesis that a defendant described as a "high risk psychopath" by the prosecution would be judged more severely than a defendant judged as "high risk" based on other evaluation procedures was supported, but only among female jurors. Unlike prior studies, little support was found for the hypothesis that clinical opinion testimony would be more influential than actuarially based testimony for either gender. Mechanisms that may underlie the observed gender differences are discussed, as are the potential implications of these findings for civil commitment proceedings. Copyright 2003 John Wiley & Sons, Ltd.