Psychopathy-associated personality traits influence crime-scene behavior in male homicide offenders.

Purpose: We investigated whether psychopathy-associated personality traits and behavioral styles affect the manner in which homicides are committed or the motives underlying them. Materials and methods: Using three nationwide registries and an in-house homicide database based on court verdicts, we identified all cases of homicide in Sweden during the years 2007, 2008 and 2009. In 72 male offenders who had undergone assessment using the Psychopathy Checklist - Revised (PCL-R), the manner of homicide was categorized as instrumental or expressive, and the motive as belonging to one of five categories: (1) intimate-partner or family-related homicide; (2) homicide occurring during altercations, (3) robberies or burglaries, or (4) criminal conflicts; or (5) sexual homicide. Results and conclusions: Offenders who had committed homicide in an instrumental manner or with a sexual motive had higher scores on PCL-R factor 1 than offenders displaying an expressive manner or other motives, suggesting that partially adaptive personality traits influence the crime-scene behavior of the former type of offenders more than maladaptive behavioral styles.

The effect of gender on the outcome of forensic psychiatric assessment in Sweden: A case vignette study.

BACKGROUND: Previous research suggests that female violent offenders at risk of a prison sentence are more likely than their male counterparts to be assessed as having mental health problems of a nature or degree that would lead to a court requirement for hospital treatment. AIMS/HYPOTHESES: To test the hypothesis that there is bias towards hospital disposal of female compared with male violent offenders with mental disorder. METHODS: In Sweden, the National Board of Forensic Medicine oversees all assessments of mental disorder for the criminal courts. Twenty-six Board appointed forensic psychiatrists, psychologists and social workers each independently assessed six case vignettes for fit with criteria for 'severe mental disorder', a prerequisite for hospital disposal from court. Each gender neutral vignette described a person who had been convicted of serious assault and had a major mental disorder. A gender was then assigned to each offender randomly within a block design, thus varying between sets. Participants were blind to the main aim of the study and the gender variation. RESULTS: There was no significant association between gender of the person assessed and judgement that s/he had a 'severe mental disorder'. An offender depicted as having mental retardation was more likely to be assessed as at high risk of criminal recidivism if portrayed as female, regardless of the sex, place of work or level of experience of the assessor. CONCLUSION: We found no evidence of gender bias in determining appropriateness of a hospital disposal of an offender with mental disorder. The difference in assessment of recidivism according to sex of the patient was only in relation to mental retardation; further research would be needed to able to interpret this. As researchers in other countries have reported gender bias in disposals from court, our findings may provide support for a centralised forensic psychiatric assessment board and formal, on-going training. Copyright © 2015 John Wiley & Sons, Ltd.

Risk assessments and recidivism among a population-based group of Swedish offenders sentenced to life in prison.

BACKGROUND: In Sweden, the number of people serving life sentences has steadily increased. To date, few studies have examined the recidivism rate or the predictive validity of different risk assessment instruments in this group. AIMS: Our aim was to test the predictive validity among inmates serving life sentences of two different instruments used for assessing risk--the Historical, Clinical and Risk Management-20 (HCR-20), most widely used in clinical populations, and the Psychopathy Checklist-Revised (PCL-R), commonly applied in both penal and clinical settings. METHOD: Ninety-eight life-sentenced prisoners were included, 26 of whom were released during the study period. Data on risk assessments and dates for release were collected from administrative records, while recidivism data were retrieved from a national database on criminal convictions. RESULTS: Sex offenders obtained the highest scores and inmates charged with domestic violent offences obtained the lowest scores on both instruments. The released prisoners were followed for a mean period of 33 months. During this time five prisoners (19%) reoffended, four of them violently, with an average time to recidivism of 10 months. Only PCL-R Facet 4, which reflects antisocial features, was significantly associated with recidivism. CONCLUSIONS: This small, but population-based, study demonstrates that antisocial behaviour shows incremental predictive validity for reoffending among life-sentenced offenders, but other measures have little to add for this specific task. The fact that those life sentenced prisoners who reoffended did so so soon after release should prompt allocation of earlier interventions towards preventing this.

Field reliability of the Psychopathy Checklist-Revised among life sentenced prisoners in Sweden.

Although typically described as reliable and valid, the Psychopathy Checklist-Revised (PCL-R) has come under some criticism by researchers in the last half-decade due to evidence of poor interrater reliability and adversarial allegiance being reported in applied settings in North America. This study examines the field reliability of the PCL-R using a naturalistic test-retest design among a sample of Swedish life sentenced prisoners (N = 27) who had repeatedly been assessed as part of their application to receive a reduced prison term. The prisoners, who were assessed by a team of forensic evaluators retained by an independent government authority, had spent on average 14 years in prison with a mean time from Assessment 1 to Assessment 2 of 2.33 years. The overall reliability of the PCL-R (ICC(A1)) was .70 for the total score and .62 and .76 for Factor 1 and 2 scores, respectively. Facet 1-3 scores ranged from .54 to .60, whereas Facet 4 was much higher (.90). Reliability of individual items was quite variable, ranging from .23 to .80. In terms of potential causes of unreliability, both high and low PCL-R scores at the initial assessment tended to regress toward the mean at the time of the second evaluation. Our results are in line with previous research demonstrating concerns regarding the reliability of the PCL-R within judicial settings, even among independent evaluation teams not retained by a particular side in a case. Collectively, these findings question whether the interpersonal (Facet 1) and affective (Facet 2) features tapped by the PCL-R are reliable enough to justify their use in legal proceedings.

Homicide offenders 32 years later - a Swedish population-based study on recidivism.

BACKGROUND: The literature on recidivism by homicide offenders is scarce despite its importance for individuals and for society. AIMS: To establish the rate of seriously violent re-offending among homicide offenders and identify risk factors for such recidivism. METHODS: A 1970s incident cohort of all homicide offenders, sane and insane, from two regions of Sweden (N = 153) was followed up until 2007 using data from the national crime register. RESULTS: Ten per cent of the cohort (n = 15) re-offended. The mean time from index offence to recidivism was 9.4 years. Five people (3%) committed a further homicide, and it was established that another five (3%) offenders had killed before the index offence. Prospective risk factors for violent recidivism were young age, psychotic disorder, male victim, acquainted victim and intoxicated victim. CONCLUSIONS: The prevalence of repeated homicide is higher than previously reported. Victim variables and mental disorder in conjunction with substance abuse appear to be two domains of particular significance for recidivism.

Crime-scene and offender characteristics in conventional and nonconventional stranger homicides committed by male offenders in Sweden.

In Sweden, from 1990 to 2013, most homicides occurred between family members, friends or acquaintances: the annual rate of incidents between unacquainted offenders and victims ranged between 8% and 13%. In the majority of these "stranger homicides," three common motives, as defined by the precipitating event, could be identified: homicides resulting from a spontaneous altercation; homicides committed in the context of a robbery or burglary; and homicides committed in the context of a gangland conflict. The remaining minority-with uncommon or indiscernible motives-could, nonetheless, be categorized according to their nonconventional distinguishing feature: homicides characterized by the offender's ostensibly mentally aberrant behavior; homicides committed in the context of a hate offense or politically motivated offense; homicides committed in the context of a sexual offense; and homicides committed in the context of a mass killing or series of homicides. In this registry-based study of 224 incidents, "conventional" stranger homicides, defined by their commonplace motive, were compared with "nonconventional" stranger homicides, defined by their lack of such motive. The former were more often committed with an accomplice, against a male victim, whereas the latter were more often committed in a public place, after contact initiated by the offender. In the latter, offenders were less often intoxicated at the time of the offense and more often adjudged to suffer from a severe mental disorder. The subcategory of nonconventional stranger homicides characterized by the offender's ostensibly mentally aberrant behavior corresponded largely to both the archetypal stranger-homicide construct and the popular notion "act of madness."

Swedish child homicide investigations: A population-based study 1998 to 2017.

BACKGROUND: Child homicide investigations are intricate, and the forensic examinations are of paramount importance in such cases. Despite this, the forensic profile of child homicides remains unexplored. OBJECTIVE: Our objective was to provide an overview of the forensic aspects and investigational challenges in Swedish child homicide cases spanning from 1998 to 2017, with a specific focus on enhancing investigative methods. PARTICIPANTS AND SETTING: 70 cases with 82 victims (41 girls, 41 boys) aged between 0 and 14 were included. METHOD: Police, crime scene and autopsy reports of solved Swedish child homicides were retrospectively reviewed. RESULTS: On average, 3.5 cases (4.1 victims) occurred annually, primarily within families (79 %). Notably, the number of cases increased by 10 % during the latter half of the study period (2008-2017) compared to the initial decade (1998-2007). In nearly 29 % of instances, the perpetrators followed the homicides with their own suicides. A majority of child deaths (89 %) resulted from concentrated acts of violence, most frequently involving blunt or sharp force. Furthermore, 66 % of the homicides took place within the parental home. Adequate crime scene processing, including documentation and evidence collection, occurred in 74 % of cases. The investigation unveiled several complicating factors: 22 % of victims and 47 % of crime scenes displayed no obvious signs of violence. Moreover, offenders often made physical (27 %) and verbal (26 %) attempts to mislead investigators. CONCLUSIONS: In conclusion, most child homicides are familial in nature and associated with investigational complexities that can lead to misdirection. This research may inform procedural recommendations for child homicide investigations, but further exploration is needed to better understand the forensic characteristics of suspicious child deaths.

Mental Disorders and Intimate Partner Femicide: Clinical Characteristics in Perpetrators of Intimate Partner Femicide and Male-to-Male Homicide.

Intimate partner violence against women is a global and persistent public health issue. An extreme manifestation of this problem is intimate partner femicide (IPF), the killing of a woman by a male partner. While declining trends of homicide rates have been observed over decades, rates of femicide and IPF have remained stable. Yet, IPF as a phenomenon has until recently been fairly invisible in Europe, why research from the European countries on rates and characteristics of IPF has been relatively scarce. One area of research, particularly in need of further scrutiny, is to what degree perpetrators of IPF suffer from mental health conditions, and what the clinical features are. The objective of present study was to add to the existing literature by investigating prevalence and types of mental disorders in perpetrators of IPF, and to compare with male-to-male homicide (MMH) perpetrators. Our aim was also to examine life-time contact with psychiatric services, and, with missed opportunities in mind, contacts shortly preceding the homicide. With a retrospective design, this population-based study includes all solved cases of male-perpetrated homicides against intimate female partners (IPF) and other males (MMH) committed in Sweden between January 2007 and December 2009. Primary and secondary psychiatric diagnoses based on ICD, version 8, 9 or 10 from psychiatric inpatient as well as outpatient care have been retrieved. In order to identify mental disorders in perpetrators during commission of the homicidal offense, we also retrieved diagnoses from forensic psychiatric evaluations. Our results demonstrate that approximately one-third of the perpetrators, irrespective of homicide type, had been diagnosed with a mental disorder (excluding substance related disorders) at some point in life. Diagnosis of substance related disorders from psychiatric care was significantly more common in MMH perpetrators (37%) compared to IPF perpetrators (15%). Similarly low rates of major mental disorder were found in both groups (11%) when aggregating life-time diagnoses and diagnoses during commission of the crime. However, homicide-suicide in connection to the offense was relatively common in IPF perpetrators (20%). Thus, our study supports the notion that previous suicide attempts and suicide ideation are important indicators for predicting and possibly preventing IPF.

Violent behaviour by general psychiatric patients in Sweden - validation of Classification of Violence Risk (COVR) software.

The objectives of the study are to report the 20-week base rate of violent behaviour in the community among a general psychiatric patient population from Stockholm and to establish the validity of a violence risk assessment software program, Classification of Violence Risk (COVR), in a European setting. Three hundred and thirty one patients at two psychiatric hospitals in Stockholm were interviewed upon discharge. Telephone interviews with the patients and collaterals were conducted 10 and 20 weeks later. The violent behaviour was also measured through a national criminal register. The allocation of patients into different risk groups according to COVR software was compared with the occurrence of actual acts of violence during the follow-up. The base rate of violent behaviour was 5.7% and a ROC-analysis showed that the AUC for COVR was 0.77. Since there were few patients in the high risk groups, the 95% confidence interval for the proportion of violent patients was wide. The base rate of violent behaviour is relatively low in Sweden and prediction is therefore difficult. The predictive validity of COVR software is comparable to other risk assessment tools.

Violent victimization of psychiatric patients: a Swedish case-control study.

OBJECTIVES: To report the rate of violent victimization of psychiatric patients 1 year before interview and to examine the relative rate in comparison to the general population. METHOD: Cases were recruited from two public psychiatric hospitals in Stockholm County (n = 390). The controls comprised gender- and age-matched people interviewed in an annual national survey of living conditions (n = 1,170). RESULTS: Twenty percent of the patients had been victimized during the preceding year. The relative rate was six times higher than that of the controls. Women appeared to be most vulnerable with a tenfold risk increase. CONCLUSIONS: The findings stress that psychiatric patients are vulnerable to other people's violent behaviour.

Criminal mutilation in Sweden from 1991 to 2017.

We identified 43 cases of mutilation homicides in a nationwide population-based study in Sweden during the period of 1991-2017. 70% of cases were classified as defensive mutilations where the main motive was disposal of the body, while 30% were classified as offensive, that is, due to an expression of strong aggression, necro-/sexual sadism, or psychiatric illness. In comparison with a previous study covering mutilation homicides in Sweden between 1961 and 1990, we noted an increase in incidence. The percentage of cases involving mutilation had increased from 0.5% of all homicides in the 1960s to 2.4% in the 2010s. The most common cause of death was sharp force, but in 28% of the cases, the cause of death could not be determined. The clearance rate in cases of mutilation homicide was 67%, and in a large majority of the cases, the offender was known to the victim. With regards to gender women made up 44% of the victims, whilst men constituted 56% of the victims and a total of 95% of the offenders. Half of the offenders had a personality disorder, however, only 13% were sentenced to forensic psychiatric care.

A Static-99R Validation Study on Individuals With Mental Disorders: 5 to 20 Years of Fixed Follow-Up After Sexual Offenses.

'The Static-99R is one of the most commonly used risk assessment instruments for individuals convicted of sexual offenses. It has been validated for use on many populations, but few studies specifically target and describe individuals with mental disorders. Additionally, research on the discriminative properties (how well the instrument separates recidivists from non-recidivists) of the instrument over longer follow-up periods is scarce. This article evaluated the validity of the Static-99R using a cohort of individuals with mental disorders convicted of sexual offenses in Sweden (N = 146) with fixed 5-year (n = 100), 10-year (n = 91), 15-year (n = 79), and 20-year (n = 36) follow-up periods. A Static-99R cut score of 6 demonstrated the highest Youden index, maximizing sensitivity (72.7%) and specificity (74.2%), with 25.8% of recidivists correctly assumed to reoffend sexually and 95.7% of non-recidivists correctly assumed not to. The Static-99R instrument demonstrated adequate discrimination (AUC = 0.79, CI 95% = 0.70-0.87, and OR = 1.45, CI 95% = 1.14-1.84, p < 0.001, 5-year fixed follow-up), with only marginal differences for 10-, 15-, and 20-year fixed follow-up (AUC = 0.73, 0.74, and 0.74 and OR = 1.31, 1.36, and 1.40, respectively). Calibration (quantifying risk and correspondence with the instrument's norms) was acceptable (Brier = 0.088, P/E = 0.70, E/O = 1.43), with the routine sample norms displaying a decisively better fit to the study cohort compared to the high-risk/high-need sample norms. The results affirm the recommendation that, when in doubt and where there is no recent local norm group large enough available, the Static-99R routine sample found in the evaluators' workbook should be used.

Association between homicide injury severity and benzodiazepine influence.

There are case reports of offenders inflicting excessive injuries on their victims when under the influence of benzodiazepines. However, the potential association between benzodiazepine influence on the offender and victim injury severity in a general homicide population has not been studied. We investigated associations between offender positive testing for benzodiazepines or z-drugs (zolpidem, zopiclone and zaleplon) and victim injury severity. Data were drawn from 95 Swedish homicide cases from 2007-2009 in which offenders had known toxicology. There were no significant differences in injury severity between cases in which the offender tested positive vs. negative for benzodiazepines/z-drugs. Thus, the findings do not support the hypothesis that there is an association between benzodiazepine influence on the offender and victim injury severity in a general homicide population.Key pointsSome previous studies have linked benzodiazepines to aggression, violence and excessive homicide injuries.The present study analysed the association between homicide injury severity and benzodiazepine status of the offender.Offenders who tested positive for benzodiazepines did not inflict more severe injuries on their victims.These findings do not support the hypothesis that benzodiazepine influence generally causes offenders to inflict more severe injuries on homicide victims.

A 24-Year Follow-up Study on Recidivism in Male Mentally Disordered Sexual Offenders With and Without Psychotic Disorders.

There is a lack of knowledge on mentally disordered sex offenders (MDSOs) targeting adult victims, especially regarding recidivism patterns and the specific subgroup with psychiatric disorders. This paper presents index offense data, clinical data, and recidivism patterns over up to 24 years in a cohort of 146 MDSOs, with and without psychotic disorders, sentenced in Sweden between 1993 and 1997. At the time of the offense, all offenders were affected by clinical, developmental, and criminal history factors. MDSOs with psychotic disorders only marginally differed from those without, the former being less likely to have been institutionalized during childhood, intoxicated during the index offense, or diagnosed with a personality disorder, substance use disorder, or paraphilic disorder. In the cohort, 3.4% of the MDSOs were reconvicted for a new sex offense over 2 years, 9.6% over 5 years, 13.0% over 10 years, and 17.1% over the entire follow-up period of 24 years. In MDSOs with psychotic disorders, no subjects were reconvicted during the first 2 years, while 2.6% were reconvicted over 5 years, 5.3% over 10 years, and 7.9% over 24 years. Recidivism rates for violent and general reoffenses were 39.0% and 37.7%, respectively, for the cohort of MDSOs, and subjects with psychotic disorders reoffended significantly later in general offenses. In conclusion, MDSOs with psychotic disorders showed the same recidivism pattern as MDSOs without psychotic disorders. Furthermore, recidivism research may preferably focus on follow-up periods of 5-10 years since most offenders appear to recidivate within this timeframe.

Homicide injury severity in association with the victim-offender relationship.

There are previous studies that have found associations between specific injury patterns and different victim-offender relationships (VORs) in homicides. We have used quantitative injury severity scores to further investigate this issue. The amount and severity of injuries were assessed in 178 Swedish homicide victims, retrospectively included from the years 2007-2009. We analyzed whether different injury measures could be used to predict the VOR. In addition to a deeper understanding of violent behavior, such associations may be of help to homicide investigators for offender profiling. The victims' injuries were assessed with eleven different methods. The cases with known VORs were divided into four categories: partner, relative, acquaintance, and stranger. The injury severities were then compared between these categories. No relevant differences were found. Thus, the current study does not support the claim that the VOR can be predicted from the injury severity in a general homicide population. These findings are in contrast to the results of some previous studies but confirm those of others.

Injury-Related Healthcare Use and Risk of Filicide Victimization: A Population-Based Case-Control Study.

Research on child-related risk factors for filicide is scant. We investigated whether prior healthcare use for injury (including poisoning) influences filicide risk. Victims (0-14 years; n = 71) were identified in a national autopsy database for the years 1994-2012 and compared to matched, general population controls (n = 355). Healthcare use data were retrieved from a national patient registry. Risks were estimated using odds ratios (ORs) and 95% confidence intervals (CIs). For females, prior inpatient care for injury conferred a statistically significant sevenfold risk (OR = 6.67 [95% CI: 1.49-29.79]), and any prior injury-related healthcare use conferred a statistically significant fourfold risk (OR = 3.57 [95% CI: 1.13-11.25]), of filicide victimization. No statistically significant risks were found for males. Healthcare personnel should be aware that children treated for injuries, especially females, may be at an elevated risk of filicide victimization. Nevertheless, the filicide base rate remains low, and parents may be stigmatized by unfounded alerts; thus, prudent reflection should precede reports to the authorities.

Male-on-Female Sexual Homicides in Sweden, 1990 to 2013: A Population-Based Controlled Study of Incidents, Victims, and Offenders.

To date, systematic studies of sexual homicides from Europe are scarce, in which none have been conducted in Sweden. This study aims to describe male-on-female sexual homicides in Sweden and differentiate from corresponding nonsexual homicides. Unsolved and solved sexual homicide (n = 33) cases were identified in a database containing all homicides in Sweden between 1990 and 2013 (N = 2,126), and subsequently data from forensic psychiatric evaluations were collected for convicted offenders. Male-on-female sexual homicides constituted 1.6% of all homicides and the clearance rate was 82%, which is comparable with the 83% overall clearance rate but took longer time to solve. Three factors differentiated sexual from nonsexual homicides: strangulation, younger age of the victim, and the absence of eyewitnesses. In solved cases, distance from the offender's home to the crime scene was strongly correlated with time to clearance. A majority of the offenders suffered from personality disorders, while other diagnoses were uncommon.

Pre-offense alcohol intake in homicide offenders and victims: A forensic-toxicological case-control study.

BACKGROUND AND AIM: Alcohol is associated with violent behavior, although little is known regarding to what extent alcohol increases homicide risk. We aimed to estimate risks of homicide offending and victimization conferred by the presence of ethanol in blood by using toxicological data from homicide victims and offenders and from controls who had died in vehicle-related accidents. METHODS: From nationwide governmental registries and databases, forensic-toxicological results were retrieved for victims (n = 200) and offenders (n = 105) of homicides committed during the years 2007-2009 and individuals killed in vehicle-related accidents (n = 1629) during the years 2006-2014. Ethanol levels in blood exceeding 0.01 g/100 ml were considered positive. RESULTS: Using logistic regression, we found that the presence of ethanol in blood conferred a significantly increased risk of homicide offending (age-adjusted odds ratio [aOR] = 3.6, 95% confidence interval [95% CI] = 2.3-5.6) and homicide victimization (aOR = 2.1, 95% CI = 1.4-3.0). After stratification by sex, risk estimates in females were about 3-fold greater than in males for both homicide offending ([aOR = 11.0, 95% CI = 2.4-49.8] versus [aOR = 3.1, 95% CI = 1.9-4.9]) and victimization ([aOR = 5.4, 95% CI = 2.4-12.2] versus [aOR = 1.7, 95% CI = 1.1-2.8]). Sensitivity analyses yielded similar estimates. CONCLUSIONS: The results of the present study are consistent with prior findings suggesting alcohol to be an important risk factor for homicide offending and victimization. Surprisingly, however, associations were more pronounced in females, although additional studies that control for potential confounders are warranted to facilitate speculations about causality.

Self-reported violent ideation and its link to interpersonal violence among offenders with mental disorders and general psychiatric patients.

This study aims at comparing mentally disordered offenders and general psychiatric patients regarding violent ideation and at exploring its association with interpersonal violence. We recruited 200 detainees undergoing forensic psychiatric evaluation and 390 general psychiatric patients at discharge. At baseline, they were asked about violent ideation; at the 20-week follow-up, information about violent acts was gathered from crime conviction registry, interviews, and records. The lifetime prevalence of violent ideation was 32.5% for offenders and 35.6% for patients; the corresponding two-month prevalence was 22.5% and 21.0%, respectively. For the both samples combined, those with violent ideation in their lifetime were significantly more prone to commit violent acts during follow-up than those without such ideation, OR = 2.65. The same applied to the patient sample, OR = 3.41. In terms of positive predictive values, fewer than 25% of those with violent ideation committed violent acts. Contrary to our hypothesis, the prevalence of violent ideation did not differ significantly between offenders and patients. However, there was support for the hypothesized association between violent ideation and violent acts on a group level. On an individual level, the clinician should consider additional factors when assessing the risk for violent acts.

Psychotropic Medications in Swedish Homicide Victims and Offenders: A Forensic-Toxicological Case-Control Study of Adherence and Recreational Use.

OBJECTIVE: We aimed to assess the extent to which adherence to, and recreational use of, psychotropic medications influence the risk of homicide offending and victimization. METHODS: We conducted a population-based case-control study by way of linking a nationwide registry of dispensed prescriptions with a forensic-toxicological database. Homicide victims (n = 200) and offenders (n = 105) were identified for the years 2007-2009 and vehicle-accident controls (n = 1,643) for the years 2006-2013. The occurrence of congruence and incongruence between dispensed prescriptions and toxicology was used as a measure of adherence and recreational use. RESULTS: For antidepressants, incongruence-but not congruence-between dispensed prescriptions and toxicology was associated with a significantly increased risk of homicide offending (odds ratio adjusted for age and sex [aOR] = 6.2; 95% confidence interval [CI], 3.3-11.6) but not homicide victimization (aOR = 0.8; 95% CI, 0.3-2.0). For antipsychotics and mood stabilizers, a significantly increased risk of homicide offending was associated with incongruence between prescriptions and toxicology (aOR = 7.0; 95% CI, 2.8-17.7), whereas risk estimates for congruence were not significantly elevated for either homicide offending or victimization. For GABAergic hypnotics, congruence and incongruence were significantly associated with increased risks of both homicide offending (aOR = 5.4; 95% CI, 2.6-11.0 and aOR = 4.9; 95% CI, 2.6-9.3, respectively) and homicide victimization (aOR = 2.1; 95% CI, 1.1-4.2 and aOR = 3.2; 95% CI, 1.7-6.1, respectively). Sensitivity analyses with a subset of controls yielded similar estimates. CONCLUSIONS: Nonadherence to medications used to treat affective and psychotic disorders appears to elevate the risk of homicide offending. Both medicinal and recreational use of GABAergic hypnotics appears to elevate the risk of homicide offending and victimization. In summary, vigilance regarding adherence to medications prescribed for mood disorders and psychosis, as well as restrictiveness regarding licit and illicit access to addictive hypnotics, might contribute to a reduction of homicidal violence.