A systematic analysis of secondary DNA transfer.

The Nature letter by R. van Oorschot and M. Jones (1) addressed two topics: the primary transfer of DNA from person to person or to various objects, and the secondary transfer of DNA through an intermediary. Forensic scientists have described the primary transfer of DNA and other biological evidence for many years. However, the authors also reported detecting secondary transfer of DNA from an object to a person's hands, which could adversely affect DNA typing in the forensic context. The prospect of secondary transfer raises questions of interest to both the legal and forensic communities. Therefore, we sought to evaluate parameters potentially leading to secondary DNA transfer. Our data do not support the conclusion that secondary transfer will compromise DNA typing results under typical forensic conditions.