Analysis of touch DNA in forensic genetics with special emphasis on deposition and sampling

A review of trace “Touch DNA” deposits: Variability factors and an exploration of cellular composition

“…As many as 1000 cells/cm 2 /hr [118] may be shed by an adult human, in a process of active desquamation which occurs continuously [119], resulting in up to 10 9 corneocytes deposited from the body each day [120]. Some authors point out that these cells are corneocytes lacking nuclear DNA and thus should not constitute a significance source of touch DNA [11] even if recovered in large numbers. Therefore the common description of shed skin cells from hands as a putative source of touch DNA is in contrast to our basic biological understanding of the outermost layers of our hands and skin [62,110].…”

“…[7,8,9] Only occasionally thus far has light been shed on a third, more fundamental, question: Where is deposited "touch DNA" coming from? [10,11,12] The first question is of particular interest to practicing forensic laboratories, and numerous studies exist comparing recovery rates of trace DNA by collection method, usually discussing the yields from different swabbing parameters (e.g. technique [13], buffer [14,15], material [16], etc.…”