Motives, Offending Behavior, and Gender Differences in Murder Perpetrators With or Without Psychosis

Abstract

Little is known whether differences exist in motivation and reactive/instrumental offense behaviors between murder offenders with and without psychotic disorder. To contribute to better prevention strategies, the aim of this study was to investigate offense characteristics in murder offenders with a psychotic, nonpsychotic or no psychiatric diagnosis, and whether these factors differ according to sex. This data study examined the population of murder offenders between 1997 and 2005 ( N = 435) in Victoria, Australia. Apparent motive for murder was allocated to one of six classifications. Assignations of reactive versus instrumental offense categories, co-offending, victim-offender relationship were determined by review of case material. Mental health service usage and prevalence of mental illnesses were identified through data with the statewide register of contacts with the public mental health system. Of the 435 offenders, 43 (9.9%) had been diagnosed with a psychotic illness. Gender differences between and within offenders with and without a psychotic disorder were analyzed. Murder offenders with a psychotic disorder were 3.19 (95% confidence interval [CI] = [1.27, 8.03]) times more likely to be motivated by revenge than nonpsychotic offenders and those with no diagnosis (odds ratio [OR] = 2.46, 95% CI = [1.10, 5.53]). The diagnostic groups did not differ on premeditation of their offenses or prior convictions. Perpetrators with psychotic illness were significantly more likely to kill family members and others known to them. It appears that for the psychotic disorder group, the perception of having been wronged in some way is a potential risk marker for planning and committing a serious offense. Care should be taken to improve adherence and access to care to avoid possible future serious violence especially in female patients with a high burden of mental illness like schizophrenia or severe mood disorders.

Forensic psychiatric evaluation of 187 homicidal assailants with and without a schizophrenia spectrum disorder: Clinical, criminological and behavioral characteristics

“…When the motivational matrix is psychotic, the homicide is more likely to be intrafamilial (Richard-Devantoy et al, 2016), as previously also reported by others (Hachtel et al, 2018). In those cases, the crimes often took place in the victim's home.…”

Women and Men who Committed Murder: Male/Female Psychopathic Homicides

“…The relationship between major psychiatric disorders and homicide has been much debated. Although it is known that the vast majority of violent acts are committed by subjects without any history of psychiatric disorder (1), some research suggests that there is a correlation between the psychotic dimension and homicide (2‐8). Several studies showed that among those patients who suffered from schizophrenia (9‐11), also those who showed cognitive impairment or executive dysfunction, were at higher risk of committing violent acts (12), including homicide.…”

“…Homicide with a psychotic motive has some unique characteristics (5,7,14,15), even though the subject’s abilities to plan an antisocial act and to execute goal‐directed behavior do not exclude a diagnosis of schizophrenia (5). In these cases, the motive for murder is often revenge, triggered by persecutory (16) delusions (17).…”

“…Women who kill are more often diagnosed with a severe mental disorder (18,34‐37) or a personality disorder, especially borderline (38‐40), in comparison with men who commit homicide (41,42). According to some studies (5,43), homicidal women are up to 43 times more likely to have a diagnosis of schizophrenia than the general population, although there is evidence that the diagnosis of schizophrenia may also be overestimated in homicidal women, and conversely, the psychopathic dimension may be underestimated (40,44,45). In our previous research, a significant correlation was found between the psychopathic dimension and borderline personality disorder in women who committed homicide (40).…”

“…Besides the psychiatric diagnosis, it is important to point out that women usually express antisocial behavior in ways that are different from that of men (46,47). In most homicides committed by women, the victim is a family member (5,18,48,49), especially a child (where the diagnosis of the perpetrator is typically a schizophrenic disorder) (42,50,51) or their partner (34), rather than strangers who are killed more frequently by men (39,51). The psychopathic dimension seems to play a major role in those infrequent homicides committed by women who kill victims outside of their family (18).…”