Mitigating effects of psychological diagnosis and type of crime on juror decision making

Despite the increasing number of mentally ill individuals who become involved with the court system regularly, the laws and statutes regarding mentally ill defendants remain relatively ambiguous and not widely understood. The current study examined how varied psychiatric diagnosis and crime type might relate to juror decision-making processes in trials involving insanity pleas. Mock jurors read a trial transcript that varied the crime and the mental health diagnosis of the defendant. Dependent measures included verdict, defendant culpability, and attitude about the insanity defense. It was predicted that jurors would assign a less punitive verdict, rate lower on defendant culpability, and have more favorable attitudes toward the insanity defense for defendants with schizophrenia than the other groups. Additionally, it was hypothesized that jurors would assign more punitive verdict, rate higher on defendant culpability, and rate the insanity defense less favorably for defendants charged with sexual assault than those charged with physical assault. It was found that psychological diagnosis and crime type did not have a significant effect on verdict choice. However, in terms of defendant culpability, jurors perceived the behavior of bipolar defendants charged with sexual assault as more planful than schizophrenic defendants charged with physical assault. Jurors also rated the behavior of defendants with antisocial personality disorder higher in planfulness than those with bipolar disorder or schizophrenia. It was also found that crime type and diagnosis influenced juror attitudes regarding the insanity defense. Jurors demonstrated less favorable attitudes about the insanity defense for defendants perceived as less mentally ill who were charged with sexual assault. Limitations and future directions are discussed.