Alternative sweat collection for forensic drug analysis using wound dressings in drug-facilitated crimes

Date-rape drugs include many medicines and street drugs that are administered to unaware victims, who are subsequently sexually assaulted (or robbed) while under their influence. Due to drug-induced amnesia, reporting is often delayed, making toxicological analysis crucial evidence. Blood and urine are suitable for most analyses up to 1–4 days after drug administration. Sweat may provide a longer detection time, however, commercial sweat patches are not usually available at police stations where victims report such crimes. Therefore, we evaluated the utility of generally available wound dressings to collect sweat for drug analysis in forensic applications. Various dressings were tested, and results were compared with urine analyses. The detection of drugs was performed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Drugs were detected in dressings for a few days when they were no longer present in urine. Drug concentrations varied depending on the body location of the dressing and were higher in dressings worn over several days. After single doses, pseudoephedrine and codeine were detectable for at least 9 days, and dextromethorphan for up to 3 days. The drug concentrations were within the ranges of 2–83 ng/dressing for pseudoephedrine, 2–74 ng/dressing for codeine, and 1–16 ng/dressing for dextromethorphan. This work has demonstrated that wound dressings can be used for sweat collection and may serve as a valuable supplement to urine toxicology in drug-facilitated sexual assault cases or other forensic cases where several days have elapsed since the incident. This approach may increase the detectability of the crimes in question.