Enhancing the sexual assault workflow: Testing of next generation DNA assessment and Y-STR systems

Abstract Sexual assault samples are among the most difficult sample types encountered by forensic laboratories. Typically, a sexual assault sample has multiple challenges including small quantity of male DNA, relatively high quantity of female DNA, and presence of PCR inhibitors. These factors make it difficult to obtain an interpretable male profile. Therefore, there is a need for a more robust, highly sensitive, and faster method for the assessment (i.e. quality and quantity) of DNA extracts to determine optimal downstream processing methods, as well as an improve Y-STR amplification system for profiling these difficult samples. We tested newly developed tools, including a DNA quantification kit (Quantifiler ® Trio) that exhibits high sensitivity higher inhibitor tolerance and includes additional useful tools for the determination of DNA quality to inform downstream processing methodology. We also tested a new Y-STR kit (Yfiler ® Plus) with enhanced capabilities. This 27-marker kit permits rapid amplification of single source and complex casework samples. These two next generation systems can generate an improved workflow for obtaining interpretable profiles from sexual assault samples. We have successfully used the Quantifiler ® Trio and Yfiler ® Plus systems to obtain informative Y-STR profiles from challenging sexual assault sample types, including low quantity male DNA, extended interval post coital samples and samples containing high amounts of female DNA. We evaluated more routinely encountered post-coital samples collected 1–3 days after intercourse. Based on the Quantifiler ® Trio results, observed outcomes were as expected after subsequent Yfiler ® Plus and GlobalFiler TM analysis.