Homicidal poisoning series in a nursing home: retrospective toxicological investigations in bone marrow and hair.

Abstract

Homicidal poisonings remain rare and can be difficult to detect, especially in the elderly or in medical settings. In this atypical poisoning series, a young nursing assistant purposely poisoned thirteen residents of a nursing home and killed ten of them. The medications used were a mix of psychotropic medications (cyamemazine, loxapine, tiapride, risperidone, and mirtazapine), under liquid formulation, which were inducing malaise and coma. The forensic investigation included analysis of blood, urine, hair, and bone marrow and exhumations of seven corpses up to 3years after the inhumation. Hair collected from a hairbrush of a cremated victim have been analyzed. Bone marrow sample preparation was based on a liquid/liquid triple extraction. Hair were incubated after decontamination overnight at 55°C in methanol. Segmentation was possible for seven samples, except for delayed exhumation samples (n = 4) and hairbrush hair sample (n = 1). The extracts were then analyzed using gas chromatography coupled with mass spectrometry (GC-MS) for unknown screening and using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) for a targeted screening and quantification. Screenings revealed the presence of the same mix of psychotropic medications. Cyamemazine, mirtazapine, loxapine, tiapride, and risperidone hair concentrations were 6-17,458pg/mg, 74-1271pg/mg, 9-1346pg/mg, 13-148pg/mg, and 3-5pg/mg, respectively. Cyamemazine bone marrow concentrations were 229 and 681ng/g and 152-717ng/mL in blood. Patients' medications were also identified and quantified. This poisoning series provide analytical data that could support subsequent toxicological result interpretation in similar forensic cases.