11 Forensic psychiatry11.1 Crime and mental disorder
11.1.1 Offences committed by mentally disordered offenders
3 min read2 figures
Written by Resident Doctor Committee · Published
Homicide
Most people who kill are not psychiatric patients: about one in ten people convicted of homicide in England were under mental health services at the time (National Confidential Inquiry).
Homicide attributable to mental disorder is rare, about one per million people per year (0.1 per 100,000), according to Large and colleagues' 2008 analysis of England and Wales.
Acquaintances or friends are the largest victim group of perpetrators in contact with mental health services, ahead of relatives, partners, strangers and staff.
A diagnosis does not by itself establish diminished responsibility or insanity, each of which has its own legal test.
National clinical survey, 1996 to 1999
This survey covered everyone convicted of homicide in England and Wales.
Finding | Proportion |
|---|---|
Lifetime mental disorder, counting personality disorder and substance dependence | 34%, mostly never seen by services |
In contact with services in the year before | 9% |
Symptoms of mental illness at the offence | 10% (5% psychotic, 6% depressed) |
Lifetime schizophrenia | 5%, several times the general population risk of about 1% |
Lifetime affective disorder | 7% |
Lifetime alcohol dependence | 7% |
Lifetime personality disorder | 9% |
Personality disorder and schizophrenia
Disposal separates them: perpetrators with personality disorder mostly go to prison, and those with schizophrenia mostly go to hospital.
Disposal | Personality disorder | Schizophrenia |
|---|---|---|
Prison | About 92% | About 29% |
Hospital | About 4% | About 71% (hospital order) |
Across all homicide perpetrators, about 6% go to hospital. Among perpetrators with personality disorder:
About 43% had never been seen by mental health services, 28% were known but not seen in the final year, and 29% were seen in the 12 months before the offence.
About 55% had a second diagnosis, most often alcohol or drug dependence, and 45% had personality disorder alone.
Killing of children
Term | Definition |
|---|---|
Neonaticide | Killing a newborn within the first 24 hours, a descriptive term |
Infanticide | Under the Infanticide Act 1938 (England and Wales), a mother kills her child under 12 months while disturbed by birth or lactation |
Filicide | A parent kills a child of any age |
Northern Ireland has a 1939 Act, and Scotland has no infanticide offence.
Postpartum mental illness does not explain most filicide.
Sexual offences
The Sexual Offences Act 2003 (England and Wales) defines consent through choice, freedom and capacity.
Paraphilic offenders, driven by a persistent sexual interest, are a minority; most offend through antisocial attitudes, poor self-regulation, intoxication or opportunity.
Arson
Arson is criminal damage by fire under the Criminal Damage Act 1971, and can carry life imprisonment even without the aggravated, danger-to-life form.
The typical adult offender is a young, socially disadvantaged man who misuses alcohol and has low intellectual functioning.
Alcohol use disorder is the diagnosis most often found.
Personality disorder, usually antisocial (dissocial), is among the commonest diagnoses, ahead of psychosis, intellectual disability and pyromania.
Pyromania is rare and needs recurrent fire setting, fascination with fire, and tension beforehand with relief afterwards.
Motives include revenge, excitement or vandalism, concealing another crime, financial gain and, occasionally, psychiatric symptoms.
Base rates
Study | Finding |
|---|---|
Fazel and Grann, 2006, Swedish registers | About 5% of violent crime is attributable to severe mental illness |
Fazel and colleagues, 2009 meta-analysis | Schizophrenia raises the odds of violence about twofold without substance misuse and about ninefold with it |
A large relative risk in a small group adds little to total population violence.