Forensic analysis of low template and environmentally affected DNA samples

Biological samples found at crime scenes may be subject to a number of hazardous conditions. Contamination can arise from environmental factors, multiple individuals, or non-human biological sources. Collecting and analyzing this type of evidence can be challenging for forensic scientists and new methods are constantly being developed to increase the quality and quantity of extractable DNA. Advancements in these areas have allowed forensic scientists to obtain information from biological samples that formerly would have yielded poor or no results. With these advancements, new questions arise pertaining to the reliability of such information. Additionally, the ability to generate DNA profiles from new sources of biological material has driven forensic examiners to modify traditional collecting and analytical techniques. We evaluated the collection efforts of a novel collection system, the microbial vacuum (M-Vac®) system, in order to determine the efficacy of this instrument compared to the standard collection technique of swabbing. Using 100 µL of four biological fluids (blood, semen, saliva, and urine) we found that the M-Vac® System collected on average six-times as much DNA from blood and two-times as much DNA from semen compared to traditional swabbing techniques. The amount of DNA collected from saliva and urine were similar with both collection methods. In a second study, we compared the effects of the order of latent print examination and DNA collection from the same fingerprint sample. We determined that the overall quantity of DNA collected from both sets of samples was similar, however, the quality of the DNA sample suffered when the fingerprint examination was performed first. Finally, we investigated environmental effects on DNA samples via contamination from bacterial sources. We intentionally spiked human DNA samples with known concentrations of DNA from 16 of the most common bacteria species associated with decomposition. Of the bacteria tested, B. subtilis was found to produce an artifact peak in the electropherogram at the TPOX locus near the 5 allele