Two cases of fatal insulin homicide resolved using combined immunohistochemistry and immunofluorescence techniques

Diabetes is a prevalent disease in modern society. Since the development and widespread use of synthetic insulin, its therapeutic application has become globally recognized for managing diabetes. However, excessive administration of insulin may lead to fatal outcomes. The rapid pharmacokinetics of insulin in the human body, combined with the lack of distinct pathological changes, makes the forensic identification of fatal insulin overdose challenging. In this study, we present two cases of fatal insulin overdose, one with a postmortem interval of up to 28 days. Postmortem specimens were collected and analyzed. Immunohistochemical and immunofluorescence assays revealed the consistent distribution of insulin and protamine at the injection sites in both cases. Insulin and protamine particles were observed in the epidermis, epidermal cells, adipocyte membranes, inter-adipocyte spaces, inflammatory cells, and glandular structures. Toxicological analyses confirmed the presence of insulin in the injected skin, subcutaneous fat, blood, urine, vitreous humor, and bile. This study provides valuable insights and guidelines for the forensic identification of insulin overdose cases.