Cale CM, Earll ME, Latham KE, Bush GL. Could Secondary DNA Transfer Falsely Place Someone at the Scene of a Crime? J Forensic Sci 2016;61(1):196–203

Sir,

We would like to comment on the paper by Cale et al. In this paper, the authors evaluated whether the increased sensitivity of current DNA profiling methods could lead to an increased detection of DNA, secondarily transferred to a knife handle following hand-to-hand contact. While the core results of their study add to our understanding of DNA transfer and persistence, in our opinion some of the claims made in the paper, and in subsequent commentaries in scientific and popular media overstate the implications of the results obtained and do not fully acknowledge the many relevant studies that have been conducted since the original discovery of secondary transfer of DNA left by touch in 1997. It is our concern that the methodology employed substantially overestimates the true rate of DNA transfer, and thus, the conclusions drawn and commentary made about the study are not an accurate reflection of such occurrences in casework situations...