Evaluation of Collection Methods for Extraction of Trace Amounts of DNA from Cloth Substrates

Abstract

DNA analysis has become the golden standard in many crime laboratories around the world. As technology advances, new possibilities arise in using evidence left at crime scenes, touch DNA being one of these possibilities. Touch DNA, available in trace amounts, is often available on surfaces handled at a crime scene. Due to the limited amount of DNA in these samples, recovery efficiency is crucial if the samples are to be used as evidence in an investigation. Fabric was chosen as a substrate for its high prevalence in everyday life. A common technique of recovery from these materials is cutting extraction, however several additional methods are available. A total of 5 methods (cutting, tape lifting, and 3 swab types) were evaluated for their efficiency in recovery of DNA from these fabric substrates. Known amounts of DNA were spotted onto marked fabric during the first portion of the study in order to estimate the percentage of DNA recovered. In the second portion, volunteers were asked to wear garments to put this information into real world perspective. While cutting was the best option for most of the substrates in the laboratory portion, no one method showed greater efficiency among all the garments in the real world portion. The majority of samples from the garments were sufficient for STR typing, according to the limit of detection given by the PowerPlex multi-locus STR kit.