Juror Attitudes Towards the Insanity Defense and The Influence of Mental Health Diagnoses on NGRI Verdicts​

Madison Gesualdo

Co-Presenters: Individual Presentation

College: College of Liberal Arts

Major: BA.PSY/FORENSICPSY

Faculty Research Mentor: Franklin Turner

Abstract:

Public perceptions of the insanity defense may shape juror decision-making and influence not guilty by reason of insanity (NGRI) verdicts across different mental health conditions. This study examines how juror attitudes toward the insanity defense relate to verdict likelihood and decision confidence when defendants present with varying psychiatric diagnoses. The primary objective is to determine whether preexisting beliefs about the insanity defense predict differential NGRI outcomes across diagnostic categories. Using a between-subjects experimental design, adult participants will complete an online survey in the role of mock jurors. Participants will first complete the Insanity Defense Attitudes-Revised (IDA-R) to assess baseline attitudes toward the insanity defense. They will then be randomly assigned to read one of four case vignettes describing a defendant pleading NGRI, each featuring a different condition: dissociative identity disorder, schizophrenia, borderline personality disorder, or a control condition involving acute psychosis without a documented mental health history. After reviewing the vignette, participants will rate their likelihood of rendering an NGRI verdict and their confidence in that decision using Likert-scale measures. Demographic variables, including race, gender, and political affiliation, will be collected to explore potential moderating effects. Findings from this study are expected to clarify how attitudinal bias and diagnostic framing influence juror verdicts in insanity cases. These results may inform legal practice, jury education, and future research on fairness in criminal responsibility determinations.
Keywords: insanity defense, NGRI, juror attitudes, mental disorders, legal decision-making