Evaluation of Sweat as an Evidential Specimen in Drug-facilitated Sexual Assault

Abstract

Drug-facilitated sexual assault (DFSA) investigations can be hindered by delayed reporting or victim unwillingness to fully participate in a physical examination. In turn, biological evidence collected to prove incapacitation at the time of the incident can be difficult to obtain. Sweat was evaluated as a specimen type for confirmation of DFSA agents. A methanol extraction paired with qualitative liquid chromatography-tandem mass spectrometry (LC/MS/MS) analysis was developed and validated for the analysis of sweat patches. Eight sedatives that are commonly-encountered in DFSA cases were included in the method panel. In addition, a preliminary study was completed to assess the effectiveness of sweat patches in practical DFSA situations. One subject took 50 mg diphenhydramine and sweat patches were applied upon dosing, after 1 d, and after 3 d to simulate delayed reporting. Sweat patches were compared to urine samples taken at 1 d, 3 d, and 7 d to evaluate differences between specimens. Method validation successfully characterized limit of detection, carryover, interference, matrix effects, and stability. All sweat patch samples from the preliminary study, including those with delayed application, contained detectable diphenhydramine in an amount > 0.75 ng/patch, while only the urine sample taken at 1 d contained > 7.5 ng/mL diphenhydramine. These results suggest that sweat may be more effective than urine for the detection of some DFSA compounds in cases of delayed reporting. As noninvasive and cumulative collection devices, sweat patches may prove to be appealing to both toxicologists and DFSA victims during DFSA investigations.