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

Since the end of the 1990s contact traces from skin have become an integral component of forensic genetics. This article is intended to give the reader an overview of touch DNA in forensic genetic stain analyses. Definitions, possible sources of touch DNA and factors that influence the outcome of the analysis are discussed and parameters for deposition, persistence and recovery are explained. An understanding of the principles behind these factors is a prerequisite for selecting an appropriate sampling method depending on the crime scene parameters and the type of surface of relevant items. A variety of sampling methods are presented and spatial and temporal strategies for collecting touch DNA are discussed.