Evaluation and modification of a micromanipulation technique and stubbing method for the collection of touch DNA

Abstract

Touch DNA is the essence of Locard’s Exchange Principal at a microscopic level – when two objects come into direct contact there is an exchange of materials. Tapelifting has been shown to be the superior method for the collection of touch DNA, in part because it excludes common PCR inhibitors. This study looked into refining the tapelifting method using a modified aluminum stub that is often used in gunshot residue collection or scanning electron microscopy. This stubbing method provides barriers that reduce the risk of contamination, such as the distance between collector and evidence. Substrates that were used for collection included wood, clothing, and writing utensils. In addition, this study looked at a micromanipulation technique that involved the collection of bioparticles using a water-soluble adhesive, while being viewed under a microscope. There were modifications made to the micromanipulation protocol that was outlined by Farash et al. in their paper. One modification was the inclusion of the extraction and quantification steps. PrepFiler Express and PrepFiler Express BTA extraction kits were both used to compare any differences. The PrepFiler Express yielded more results, including the only full profile. The micromanipulation technique and the stubbing method both proved to be adequate methods for the collection of touch DNA.