A quantitative evaluation of forensic sampling tools and extraction methods

Forensic sampling of bodily fluids is commonly performed by means of swabbing and occasionally tape-lifting. Current research focuses on comparative studies of commercially available swab types, and alternative methods are rarely investigated. Little is known about the underlying sampling mechanism and the parameters involved in sampling performance. The goal of this study was to gain additional information on said sampling mechanisms while investigating alternative sampling tools. To this end, three filters made of different materials were used and compared to conventional cotton swabs to sample both microparticles and DNA from a glass substrate. By splitting the particle-sampling process into collection and extraction, it was found that the extraction step was primarily limiting the overall performance. Additionally, three different extraction methods were evaluated, namely ultrasonication, vortexing, and centrifuging, generating a total of 12 different tool-extraction combinations. Polyvinylidene fluoride (PVDF) filter papers and cotton swabs were similarly capable of sampling particles when ultrasonication and vortexing were applied, respectively. In contrast, sampling DNA showed varying results. It is concluded that a combination of micro- and nanoscopic principles determines the overall efficiency.