An experimental study on hand injury in beer bottle assault: A perpetrator perspective

The risk and pattern of self-inflicted injuries to perpetrators in assaults involving beer bottles remain insufficiently characterised. In particular, the distinction between the use of intact and deliberately broken bottles may be of medico-legal relevance. In this experimental study, hand contacts with glass fragments were investigated during simulated assaults using intact and broken beer bottles. Thirty-two striking experiments with intact bottles and thirty stabbing experiments with broken bottles were performed. Contact-positive tests were more frequent in the broken-bottle stabbing condition than in the intact-bottle striking condition (13/30 vs. 8/32), but the difference did not reach statistical significance in the primary two-sided analysis of contact events per test (Mann-Whitney U = 380.0, p = 0.095). Interdigital flap involvement was rare in striking experiments (1/32) but markedly more frequent in stabbing experiments (8/30; Fisher's exact p = 0.011). A sensitivity analysis showed a significant difference between conditions (U = 326.0, p = 0.026). CT-based measurements demonstrated structural differences between bottle types, with one bottle type showing greater neck length and mass. Complete fragmentation during striking occurred only in this bottle type. Exploratory statistical analyses within the broken-bottle group did not identify a significant association between contact occurrence or localisation and fracture morphology, spike length, or force-plate readings. The findings suggest that the anatomical distribution of hand contacts, particularly involvement of the interdigital region and the volar and lateral aspects of digit II, may be more informative than their mere occurrence in the forensic evaluation of assault scenarios involving glass bottles.