Date of Graduation
Eberly College of Arts and Sciences
Forensic and Investigative Science
Over the last several years, crime laboratories have largely focused on the sexual assault kit (SAK) backlog, where they are often confronted with many low-quality samples. The lack of available screening techniques has prevented analysts from gaining insight into the disposition of the sample earlier on in the testing process; requiring analysts to rely on visual observations and little background information. Consequently, resulting in the hindrance of probative STR profiles while expending a large amount of time and resources to gain this result. In recent years, crime laboratories have explored a male screening technique, recommended by SWGDAM, to combat this problem. However, it is important to investigate alternative screening methods that can be performed prior to receiving the evidence at a crime laboratory, allocating time and resources toward enhanced testing of probative samples.
Mock sexual assault admixtures were prepared at different mixture ratios and split into two data sets. The first data set was comprised of 24 total samples that were prepared at the 1:10 and 1:20 mixture ratio, then run on the RapidHIT® 200. The second data set consisted of 91 total samples that were prepared at the following mixture ratios: 1:5, 1:10, 1:15, 1:20, 1:25. These samples were then run on the ParaDNA® System with the Intelligence Test assay.
The results of this study showed that the RapidHIT® 200 outperformed the ParaDNA® Intelligence Test when utilized to screen sexual assault admixtures in a non-laboratory setting. The RapidHIT® 200 was successful at detecting a mixture profile in 75% of the mock sexual assault cases. Whereas, the ParaDNA® Intelligence Test had less than one in four chance of detecting the presence of a mixture. In other words, the linear mixed-effects model demonstrated that the instrument used for screening sexual assault samples in a non-laboratory setting does have a significant effect on the proportion of loci that exhibit a mixture. In conclusion, the ParaDNA® Intelligence Test is not recommended for use in a non-laboratory setting. Although the RapidHIT® 200 outperformed this test, further research should be conducted before use in any setting.
Koepfler, Taylor L., "Screening Sexual Assault Evidence with Low Concentrations of Male DNA Utilizing the RapidHIT 200 and ParaDNA Intelligence Test" (2019). Graduate Theses, Dissertations, and Problem Reports. 7467.