Juror decision-making regarding a defendant diagnosed with borderline personality disorder

Stigma is an established consequence of the Borderline Personality Disorder (BPD) diagnosis. This diagnosis is subject to revision in the International Classification of Diseases-11th Revision (ICD-11). Using the legal issue of diminished responsibility, this study applied an experimental mock-jury methodology to explore the impact of diagnostic stigma of BPD on jury decision-making. Participants were allocated to one of two versions of a simplified fictitious homicide trial. The group whose defendant was described as having a 'severe personality disorder, borderline pattern' rated the defendant as more dangerous, and more in need of segregation and coercive treatment, than controls where the defendant was described as having a 'complex mental health problem'. Between-group differences in other measures, including the decision to agree a verdict of diminished responsibility, were not found. The ICD-11 'severe personality disorder, borderline pattern' diagnosis may adversely impact the attitudes of jurors considering the question of diminished responsibility.