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Effective Long-term Preservation of Biological Evidence

NCJ Number
Date Published
June 2014
153 pages
This report presents the findings and methodology of a research project whose goal was to identify the optimum method for preserving DNA associated with forensic evidence, using commercial off-the-shelf (COTS) chemical preservatives that have long been used in the food and cosmetics industries.
This project tested the hypothesis that the use of COTS preservatives on cotton swabs following DNA collection would reduce the risk of DNA degradation and would result in improved profile quality or increased peak height values of analyzable alleles. Four main categories of chemical preservatives were tested: nuclease inhibitors, anti-microbial agents, chelators/fixatives, and antioxidants. The study demonstrated that COTS preservatives can be used to protect DNA from degradation. Specifically, Sodium Azide, Parabens, EDTA, Zinc, and Propyl Gallate generated peak high values that showed statistically significant increases when compared with the untreated control samples. In addition, statistically significant differences were observed from most of the preservative-combination treated samples when compared with the untreated control samples. In Phase III of the research, successful direct amplification of treated blood samples was achieved with Promega's PowerPlex Fusion kit. Phase I consisted of real-time aging and accelerated aging studies that tested 12 chemical preservatives individually with forensically relevant fluids. In Phase II, the preservatives that showed the most promising results were combined to examine whether this would improve the efficacy of the preservations. Phase III examined Zinc and Zinc-EDTA in conjunction with collection substrates that lent themselves to direct amplification. In order to perform these novel mechanisms for preserving biological evidence, no expensive instruments or specialized skills are required, and the techniques can be adopted by any state crime laboratory regardless of funding level. 58 figures, 21 tables, 67 references, and appended forensic index data

Date Published: June 1, 2014