Juror decision making in not criminally responsible on account of mental disorder trials: Effects of defendant gender and mental illness type

This study sought to examine the potential impact of defendant gender and mental illness type on Canadian juror decision making by manipulating the gender (man, woman) and mental illness (substance abuse disorder, schizophrenia, bipolar, depression) of the defendant in a second-degree murder case involving an insanity plea. Participants read a trial transcript that included definitions of second-degree murder and the not criminally on account of mental disorder (NCRMD) defense. Participants then provided a verdict (guilty or NCRMD) and completed various scales measuring attributional judgments, perceptions of the defendant, and perceived dangerousness. Contrary to expectations, NCRMD was chosen over a guilty verdict in the majority of cases. Findings also indicated that participant decisions and perceptions regarding defendants diagnosed with substance abuse disorder differed from the other mental illness groups. The gender of the defendant had an influence on participants' perceptions of internal attributions, and the perceived stability of criminal behaviors. Results suggest that perceptions of mental illness influence verdicts in NCRMD cases, and that defendant gender plays a role in participants' perceptions of defendants. These findings contribute to the scarce literature on mental illness in the Canadian court system. Future research should examine the interaction between juror gender, defendant gender, and mental illness in insanity cases.