A review of trace "Touch DNA" deposits: Variability factors and an exploration of cellular composition. (March 2019) - Burrill, Julia
Highlights: Amount of DNA deposited on touched items is highly variable and difficult to predict. Ongoing research shows wide range of factors in variability of touch DNA transfer. Little known about cellular/non-cellular components and DNA origin in touch deposits. Anucleate corneocytes, free nuclei, nucleated cells, and cell-free DNA, may all be sources. Abstract: The use in courtrooms of forensic DNA typing results from presumably touched or handled items is increasing as the sensitivity of detection techniques improves. Research investigating how much DNA can be recovered from handled items, whether trace DNA can be detected under certain scenarios including varying degrees of indirect transfer, and factors which may influence these results is summarized here. Fundamentally, our current understanding of the cellular content of touch deposits and the origins of the potential trace DNA therein is extremely limited. Possible origins include anucleate corneocytes, fragmentary cells/nuclei, nucleated epithelial cells from hands, transferred nucleated cells, and cell-free DNA. Here we review the existing evidence for each possible source and consider remaining knowledge gaps regarding forensically relevant touch depositions.