DNA fingerprinting secondary transfer from different skin areas: Morphological and genetic studies.

The correct identification of the biological samples under analysis is crucial in forensic investigation in that it represents the pivotal issue attesting that the resulting genetic profiles are fully reliable in terms of weight of the evidence. The study reported herein shows that "touch DNA" secondary transfer is indeed possible from person to person and, in turn, from person to object depending on the specific sebaceous or non-sebaceous skin area previously touched. In addition, we demonstrate the presence of fragmented single stranded DNA specifically immunodetected in the vast majority of cells forming the sebaceous gland but not in the epidermis layers, strongly indicating that sebaceous fluid represents an important vector responsible for DNA transfer. In view of our results, forensic investigations need to take into account that the propensity to leave behind genetic material through contact could depend from the individual ability to shed sebaceous fluid on the skin surface.