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Rapid and Selective Extraction of Male DNA from Rape Kits and Other Forensic Evidence Using Pressure Cycling

NCJ Number
Bruce McCord
Date Published
July 2018
14 pages
With the goal of providing a rapid, reliable, and efficient method for selectively recovering sperm DNA from sexual assault evidence, this study applied pressure cycling technology (PCT) in the selective digestion of sperm cells from evidence mixtures, with an emphasis on the role of buffer composition on sperm DNA yields and increase in selectivity of extraction.
This report first describes a two-step organic differential extraction as one of the most popular methods for separating different sources of DNA encountered in a rape kit, concluding that this method is time-consuming, technique-dependent, and difficult to automate. It can also result in relatively inefficient separations of female DNA from the male sample components. In addition to the application of pressure cycling technology in the selective digestion of sperm cells from evidence mixtures, the current study also improved sample recovery from cotton swabs, which are often used to collect evidence at a crime scene; however, the inefficient sample recovery from this substrate has been examined in numerous studies. In order to improve DNA recovery and hence improve downstream genetic analysis, the effect of alkaline lyses on sample recovery from cotton swabs was studied. The alkaline lysis and PCT method described in this report uses inexpensive buffers, has a very short extraction time; and most importantly, can recover most of the DNA from the matrix. This is a significant improvement on existing methods. The equipment and procedures developed are described in detail. 5 figures, 4 references, and listed citations for the dissemination of research findings

Date Created: January 9, 2019