The Homicide Offender Motive Scale (HOMS): A classification system for homicide motives based on a qualitative systematic review.

Many types of homicide motives have been described in the scientific literature. However, inconsistencies regarding how these motives are defined and classified may hinder the ability to understand the driving factors behind homicide. Developing a classification system that defines and organizes commonly used motives into superordinate categories may improve research focused on homicide. The current study sought to develop such a classification system, titled the Homicide Offender Motive Scale (HOMS), based on a qualitative systematic review. Databases including Medline, PsychINFO, and Google Scholar were reviewed to identify all homicide motive studies published prior to February 2024. Multiple reviewers independently assessed the quality of the studies using an empirical appraisal checklist. Seventy-seven studies comprising 143 motives with varying definitions were included. The reviewers then conducted a thematic analysis to identify descriptive and analytical themes for the 143 motives described in the studies. Following empirical guidelines, the motives were synthesized into 21 descriptive themes with operational definitions and criteria. Perfect interrater reliability of these definitions and criteria was then established in an independent sample of 200 adult homicide offenders. Finally, the 21 descriptive themes were grouped into four distinct analytical themes, which were also partly based on an existing criminological classification system. The 21 descriptive themes represent commonly observed motives across different homicide cases. The four analytical themes are superordinate categorizations of the specific motives. The empirical nature of the HOMS may offer a unified typology of homicide motive for researchers to expand upon.