Defining overkill homicide through quantitative criteria: Evidence from a retrospective forensic study over a 34-year period in a Tunisian forensic center.

Abstract

The forensic identification of "overkill" homicide remains challenging due to the absence of a standardized, evidence-based definition. This study aimed to address this gap by establishing a quantitative criterion and delineating the criminological profile of overkill in the Tunisian context. A retrospective study of autopsy records collected over a 34-year period in the forensic department of the University Hospital of Monastir in Tunisia. During the study period, all the autopsied homicide cases were examined and analyzed using the autopsy reports as well as medical records and court reports. A multidisciplinary operational definition was applied. Statistical analysis included multivariate logistic regression and ROC curve analysis to identify predictive factors and determine diagnostic thresholds. Of the 297 homicides, 83 (27.9%) were classified as overkill based on a multidisciplinary operational definition integrating quantitative and qualitative indicators of excessive violence. Overkill cases were characterized by a significant overrepresentation of female victims (36.1% vs. 12.1%, p < 0.001), intimate relationships (21.7% vs. 7.9%, p = 0.002), and perpetrators acting alone with higher rates of criminal and psychiatric history. The number of fatal injuries was the sole independent predictor (OR = 16.3, p < 0.001). A threshold of ≥ 2 fatal injuries provided optimal discrimination (AUC = 0.982, sensitivity 97.6%, specificity 98.1%). This study provides an attempt to identify overkill, establishing ≥ 2 fatal injuries as a diagnostic threshold. The findings characterize overkill as distinct form of expressive violence. Despite the promising nature of our results, it is imperative that these findings be interpreted with caution and ideally correlated with other objective criteria.