Homicide-Suicide in the United States: Moving Toward an Empirically Derived Typology.

OBJECTIVE

Homicide-suicide is an extremely heterogeneous and rare form of lethal violence. In an effort to capture this heterogeneity to enhance research and prevention efforts, typologies have been developed from literature reviews or geographically limited samples. The purpose of the present study was to develop the first empirically derived typology of homicide-suicide decedents, using a large, geographically diverse sample.

METHODS

Data were used from the Centers for Disease Control and Prevention's National Violent Death Reporting System from 2003 to 2015 across 27 states. Homicide-suicide decedents were included if they were ≥ 18 years of age, they were the only victim and suspect involved, they had a known relationship with the victim(s), and the circumstances surrounding the event were known. There were 2,447 decedents that met study criteria. Unsupervised machine learning was used to classify decedents by precipitating circumstances and victim types.

RESULTS

Eight homicide-suicide subtypes were identified and cross-validated in a holdout sample. Three subtypes consisted of only intimate partner victims, 3 subtypes had a single victim type (children, extrafamilial, other family), and there were 2 multivictim subtypes: one that could be identified as familicide and the other in which there was indiscriminate killing, which often included an intimate partner. Subtypes were distinguishable by demographic and other characteristics (median area under the curve = 0.77). Relationship problems precipitated 60%-92% of homicide-suicides across subtypes, while mental health problems were recognized as a precipitant in 7%-72% of decedents across subtypes.

CONCLUSIONS

The findings expand upon and validate previously proposed homicide-suicide typologies. While relationship problems are common precipitants across homicide-suicide subtypes, known mental health problems vary across subtypes.