Forensic aspects of incised wounds and bruises in pigs established post-mortem

Recognizing post-mortem (PM) changes is of crucial importance in veterinary forensic pathology. In porcine wounds established PM contradicting observations regarding infiltration of leukocytes have been described. In the present study, skin, subcutis and muscle tissue sampled from experimental pigs with PM incised wounds (n=8), PM bruises (n=8) and no lesions, i.e. controls (n=4), were examined for signs of vitality over time. All tissue samples were subjected to gross and histopathological evaluation. Hemorrhages were present along the edges of PM incised wounds but deposits of fibrin were never observed. PM bruise led to hemorrhage in the subcutis visible on cross section of the skin in 3 out of 8 pigs. Histologically, hemorrhages in the subcutaneous tissue and disrupted muscle fibers were observed in PM bruises and could not be differentiated from similar lesions in ante-mortem (AM) bruises. Vital reactions, i.e. infiltrating leukocytes, hyper-leukocytosis and pavement of leukocytes, were absent in all incised wounds and bruises regardless of the time of sampling after traumatization. In conclusion, a vital reaction was not present in PM incised wounds, regardless of the time of sampling. Moreover, it was found that AM bruises free of leukocyte infiltration cannot be distinguished from PM bruises, an observation which is of crucial importance when timing bruises in forensic cases.