U.S. flag

An official website of the United States government, Department of Justice.

Optical characterization of epidermal cells and their relationship to DNA recovery from touch samples

NCJ Number
F1000Research Volume: 4 Issue: 1360 Dated: 2015
Date Published

This paper studies optical characterization of epidermal cells in relation to DNA recovery from touch samples.


The goal of this study was to investigate the relative contributions of different cellular and genetic components to biological samples created by touch or contact with a surface – one of the most challenging forms of forensic evidence. Although little to no extracellular or cell pellet-associated DNA was detected when individuals washed their hands prior to substrate handling, the authors found that a significant number of epidermal cells (between ~5x103 and ~1x105) could still be recovered from these samples, suggesting that other types of biological information may be present even when no amplifiable nuclear DNA is present. These results help to elucidate the biological context for touch samples and characterize factors that may contribute to patterns of transfer and persistence of genetic material in forensic evidence. Touch samples were generated by having individuals hold an object for five minutes and analyzed for quantity of intact epidermal cells, extracellular DNA, and DNA from pelleted cell material after elution from the collection swab. Comparisons were made between samples where individuals had washed their hands immediately prior to handling and those where hand washing was not controlled. The vast majority (84-100%) of DNA detected in these touch samples was extracellular and was uncorrelated to the number of epidermal cells detected. (Published Abstract Provided)

Date Published: January 1, 2015