Profiling Overkill Cases Perpetrated by Individuals With Psychotic Illness: A Cross-Sectional Study From Türkiye

Although individuals with psychosis represent a minority of homicide perpetrators, they are overrepresented in 'overkill' cases, yet little is known about the characteristics of this specific group.

To describe the characteristics of people with psychosis who not only kill another person but also use far more force than necessary to do so.

A 10-year cross-sectional clinical chart review was conducted at two major forensic psychiatry centres in Türkiye found 183 homicide perpetrators with psychotic illness whose index offences met overkill criteria, operationalised as the infliction of violence beyond that necessary to cause death. Data on background, clinical and homicide-related factors were analysed and an exploratory cluster analysis was performed.

Almost all (91%) perpetrators were men, with a mean age of 38 years and long-standing illness with impaired psychosocial functioning and prior psychiatric contact. Most usually the victim was a relative, killed in a private indoor setting with a sharp weapon, easily to hand, when the perpetrator was experiencing active psychotic symptoms. Cluster analysis confirmed two distinct subgroups: this psychosis-dominant/domestic type, but also a smaller externalising/premeditated type, these perpetrators characterised by more planning and much greater likelihood of prior involvement with crime and/or substance use and targeting peers rather than family.

The profile of overkill perpetrators with psychotic illness largely resembles that of people with psychosis who kill without excessive violence, but the identification of two distinct subgroups highlights important heterogeneity within this population. Given that the perpetrators had almost all been known to mental health services at some point, these findings should help focus assessments and guide risk management approaches, which, particularly for the domestic attacks, may include environmental strategies.