Analysis of postmortem dermal extracts is an efficient illicit drug screening method supporting forensic medicine

Forensic screening of illicit drugs is typically performed on tissue homogenates, a resource-intensive process. The elaborate, invasive nature makes this process not suited for rapid screening and elicits resistance for cultural or religious reasons in certain subpopulations. Based on earlier work regarding the sensitive detection of xenobiotics in finger sweat, we aimed to test the feasibility of postmortem non-invasive sampling as an alternative. Soaked filter paper was applied to the hands and feet of 93 deceased individuals undergoing autopsy and stored in tubes. Samples were extracted with an aqueous solution and directly measured using an untargeted LC-MS/MS workflow. Tissue samples were taken for standard toxicological assessment. 82 compounds covered by the toxicological assay were independently identified in dermal extracts. These included 19 compounds that are frequently associated with illegal use. Compared to the tissue-based assay, dermal extracts showed an average 95% positive identification overlap and 87% negative identification overlap. Surface contamination was successfully addressed by simultaneous detection of endogenous drug metabolites. In several cases, dermal extracts classified cocaine, heroin and/or ketamine consumption by presence of associated metabolites despite negative toxicology results, indicating that these drugs may persist for longer time in skin than traditional matrices. In summary, while currently limited to qualitative assessment, dermal extracts not only provide a rapid, non-invasive screening tool for the detection of drugs independent of autopsy, but may also offer a longer detection window for certain substances.