Suicidal insulin injection combined with homicidal wrist incision

Determining fatal insulin overdose remains a major challenge in forensic practice due to the absence of characteristic histopathological findings and technical limitations in postmortem insulin detection. This report presented a complex case of a 69-year-old diabetic female involved in a suicide pact with her son, who was subjected to estazolam ingestion, excessive insulin injection, and a sharp-force incised wound of the left wrist with transection of the radial artery. She survived for more than 48 h after drug administration before ultimately succumbing to fatal sharp-force trauma inflicted by her son. Immunohistochemical staining confirmed insulin deposition at injection sites, and radioimmunoassay revealed markedly elevated insulin levels accompanied by a suppressed C-peptide concentration-findings consistent with exogenous insulin administration. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) detected estazolam at a concentration of 18.2 ng/mL in blood. Forensic evidence confirmed the son's direct involvement at the scene. Based on the totality of the evidence, it was definitively concluded that the injuries were homicidal. This study offered valuable insights for the forensic identification and investigation of complex insulin-related fatalities.