INTRODUCTION: Forensic pathologists are frequently confronted with questions about whether an injury is likely to have been inflicted by an assault or be self-inflicted. However, little is known of the epidemiological variables that might be applicable to differentiate between homicides and suicides in deaths caused by single stab injuries to the trunk.

METHOD: Using the Swedish forensic autopsy register, we identified 94 homicides and 45 suicides between 2010 and 2021 in which death followed a single stab injury to the trunk. We extracted characteristics from the cases and performed statistical analyses using the Mann-Whitney U test, Chi-square test and logistic regression model.

RESULTS: Victims of homicides were younger than suicide victims (median age 33 years vs. 52 years, p < 0.05), and males were in the majority in both groups (93% vs. 82%). In numerous homicide victims, stab wounds were placed in the back and in axillar regions, unlike in suicides victims in which the stabs were all placed on the medial part of the anterior trunk. Vertical entrance wounds in the skin combined with a medially running injury channel (n = 13) showed a positive predictive value of 100% (95% CI 75.3-100) for homicide, although the sensitivity was low. Homicides were conclusively associated with an outdoor death scene (OR 19.0, 95% CI 7.6-47.1), injury to thoracic bone/cartilage (OR 3.8, 95% CI 1.6-9.0), influence of alcohol (OR 7.1, 95% Cl 2.9-17.7) and illicit drugs (OR 4.3, 95% CI 1.5-11.9).

DISCUSSION AND CONCLUSION: The observed forensic characteristics of stab injuries could be used as a tool when assessing the manner of death in single stabs. Further research on variables associated with manner of death are needed and we suggest also including characteristics of surviving victims in such analyses.