Strong evidence of drug-facilitated crimes by hair analysis using LC–MS/MS after micro-segmentation

Abstract

Hair analysis can provide effective information to prove drug-facilitated crimes (DFCs). Herein, an analytical procedure for obtaining evidence of DFCs stronger than with conventional segmental hair analysis is demonstrated for an actual case. A victim reported to the police that, approximately 1 month earlier, she had consumed a drink, fallen asleep, and then been assaulted. Her hair strands were collected to examine whether drugs were detected from her hair. Drug screening by liquid chromatography–high-resolution mass spectrometry (LC–HR-MS) revealed a specific peak, derived from zolpidem, on the chromatogram obtained from the hair extract. Micro-segmental analysis using an internal temporal marker (ITM) was performed to estimate the day of zolpidem ingestion using sensitive LC–low-resolution tandem mass spectrometry (MS/MS). The victim ingested cold medicine as an ITM twice, with an interval of 21.0 days, to calculate the actual growth rate of her hair. Her hair strands were collected again 2 weeks after the second ITM ingestion. A hair strand was cut at 0.4-mm intervals, and the distribution curves of zolpidem and the ITM in a hair strand were plotted. The estimated day of zolpidem ingestion was consistent with the day of the incident that she had reported. The two-step hair analysis proved that she had ingested zolpidem on the day of the incident. The combination of drug screening by LC–HR-MS and determination of the day of drug ingestion using micro-segmental analysis by sensitive LC–MS/MS would be useful for elucidating the relationship between the drug and the incident when investigating DFCs.