Rates of mental disorder in people convicted of homicide. National clinical survey.

Background: Previous studies of people convicted of homicide have used different definitions of mental disorder.

Objective: To estimate the rate of mental disorder in people convicted of homicide; to examine the relationship between definitions, verdict and outcome in court.

Methods: A national clinical survey of people convicted of homicide (n=1594) in England and Wales (1996-1999). Rates of mental disorder were estimated based on: lifetime diagnosis, mental illness at the time of the offence, contact with psychiatric services, diminished responsibility verdict and hospital disposal.

Results: Of the 1594,545 (34%) had a mental disorder: most had not attended psychiatric services; 85 (5%) had schizophrenia (lifetime); 164 (10%) had symptoms of mental illness at the time of the offence; 149 (9%) received a diminished responsibility verdict and 111 (7%) a hospital disposal - both were associated with severe mental illness and symptoms of psychosis.

Conclusions: The findings suggest an association between schizophrenia and conviction for homicide. Most perpetrators with a history of mental disorder were not acutely ill or under mental healthcare at the time of the offence. Some perpetrators receive prison sentences despite having severe mental illness.