Kristyn Kamke, Marianna Carlucci, Ph.D., Matthew Kirkhart, Ph.D., Theresa DiDonato, Ph.D., Frank Golom, Ph. D.

When Gender Doesn’t Match the Crime: Jury Bias in Cases of Insanity

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Many extra-legal factors, facts that are not case evidence but affect jury decisions, have been investigated in relation to decision-making, but less attention has focused on how they affect decisions in insanity defense cases (Abwender & Hough, 2001). In general, women tend to receive less severe sentences in court than a male counterpart, and there is also some evidence that women are less likely to be found guilty of crimes than their male counterparts. (Nagel & Johnson, 1994). For cases of insanity, it is less clear how defendant gender relates to assessments of guilt and sentence length (Breheney et al., 2007). When men commit crimes associated with women, like filicide, they receive harsher sentences and are more likely to be found guilty (Wiest & Duffy, 2013). It is unclear how women are treated when committing crimes associated with men, like killing a stranger; however, considering that women seem to receive harsher sentences when utilizing weapons associated with men (e.g., gun), there is reason to believe they would receive harsher sentences and verdicts when committing crimes with other factors associated with men (Dunn, Cowan, & Downs, 2006).

A total of 576 participants were used in analysis. They were randomly assigned to eight different groups, each reading a vignette describing a murder case in which defendant gender (female, male), relationship to victim (parent, stranger), and method of killing (smothering, shooting) were manipulated. Participants gave a verdict of guilty, not guilty, or not guilty by reason of insanity (NGRI), and sentenced the defendant if he or she was found guilty. It was expected that women would receive less harsh verdicts and less severe sentences than men.

No relation was found between gender of the defendant and verdict chosen, c² (1, N = 568) = 2.17, ns. However, female defendants were more likely to get NGRI verdicts. Because assumptions were violated for a parametric test, a Mann Whitney U test was conducted to the test the prediction that women would receive lesser prison sentences than men. The results of the test were in the expected direction and significant, z = -2.11, p < .05. Moderation tests could not be run because of use of the non-parametric test. Exploratory chi-squared analyses revealed significant relations between victim type and verdict, c² (1, N = 568) = 8.56, p < .01, with defendants who killed strangers getting more guilty verdicts, political affiliation and verdict, c² (1, N = 437) = 4.06, p < .05, with Democrats giving more NGRI verdicts, and personal diagnosis of mental illness and verdict, c² (1, N = 568) = 13.28, p < .001, with those who had a mental illness giving more NGRI verdicts.

These results suggest that the defendant gender may be a factor in jury decisions in insanity cases, though this study should be repeated with a larger sample size. In addition, it seems that the defendant’s relationship to the victim, political affiliation, and experience with mental illness also affect verdict decisions. These factors should be examined when selecting juries for insanity defense trials.