Degree Year


Document Type


Degree Name

Bachelor of Arts




Patty deWinstanley

Committee Member(s)

Cynthia McPherson Frantz
Sarah Rabbitt


Not guilty by reason of insanity, NGRI, Insanity defense, Legal insanity, Fair trial, Legal psychology, Pretrial attitudes, Juror decision-making, Evidence type


Pretrial attitudes (attitudes held preceding any case-specific information) towards the insanity defense are known to influence jurors’ decision-making about a case. However, the impact of pre-trial attitude on decisions across different types of evidence was an open question that the present study addressed. Through Amazon Mechanical Turk, participants indicated their pretrial support for the insanity defense. Participants served as mock jurors and rated the likelihood of giving the defendant not guilty by reason of insanity (NGRI) as well as perceived responsibility for the defendant’s actions, they gave these ratings after introducing seven different pieces of evidence (baseline case vignette, mother hospitalized for schizophrenia, defendant abused as child, defendant testimony to delusions, psychological evaluation diagnosing defendant with schizophrenia, comorbid substance abuse, brain scans supporting schizophrenia diagnosis). Pretrial attitudes had a significant effect on mock jurors’ ratings, with those in the low-support group being significantly less likely than the those with higher support to give the defendant NGRI. There was also a significant interaction between attitude groups and type of evidence. Both the effect of attitude group and the interaction between evidence type and attitude group were significant for responsibility ratings as well. The results of this study have important implications for insanity defense trials, and highlight the importance of how pretrial attitudes and different types of evidence, as well as how pretrial attitudes interact with types of evidence, influence the likelihood of a mock juror giving a defendant NGRI.

Included in

Psychology Commons