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Adaptation of the DNase I Procedure to the Biomek® NXP Robotic Platform for More Efficient and Automated Sexual Assault Sample Processing

NCJ Number
Date Published
35 pages

The author reports on a research project that was developed to address the backlogs of sexual assault casework throughout the US by developing a new differential extraction (DE) protocol to expedite, without compromising quality, the processing of sexual assault samples.


The author reports on a project that was designed to adapt, optimize, validate, and integrate a DNase I differential extraction protocol (DNase DE) into the current sexual assault casework workflow on the Beckman Coulter Biomek® NXP (NXP) automation workstations at the Virginia Department of Forensic Science (VADFS). The project focused on integrating three published manual DNase I-based protocols with current VADFS manual sexual assault DE protocol to generate a semi-automated method of performing sperm pellet clean-up, without the need for numerous pellet washes, thereby developing sperm fraction (SF) and non-sperm fraction (NSF) fractions in a more automated manner. The author addresses the question of how to optimally combine the published DNase DE protocols with the VADFS DE protocol to reduce manual steps and, as a result, the overall time, and to increase throughput. Key outcomes of the optimized semi-automated DNase DE method included: it produced Y-DNA yields and A/Y ratios comparable to the manual VADFS DE method with reduced manual steps involved; the two methods had comparable sensitivities for the SF; it demonstrated reproducibility comparable to the current manual VADFS DE method; it produced STR profiles comparable to the manual VADFS DE method, including being able to generate sole-source male profiles from SF samples; it was impacted by the presence of contaminants comparably to the VADFS DE method; and it had a low cross-contamination frequency similar to the VADFS DE method. The author suggests that the DNase DE meets the criteria for replacing the current VDFS DE method for sexual assault casework.

Date Published: January 1, 2023