Screening Sexual Assault Evidence with Low Concentrations of Male DNA Utilizing the RapidHIT 200 and ParaDNA Intelligence Test

Abstract

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

Analysis of rapid HIT application to touch DNA samples

“…To date, this technology is only permitted for the processing of single-source reference samples in a forensic capacity [11]. In a research capacity, successful application of rapid DNA technology has been applied to bone samples [12], blood samples [13], tissue samples [14], mock sexual assault kit (SAK) samples [15], and some casework samples, including drinking items, handled items, and clothing [16]. The literature is sparse regarding the DNA template and sample sources, excluding reference buccal swabs; however, results have indicated that this system performs more poorly than the highly specialized standard manual workflow [11,16,17].…”