Highly efficient sperm cell separation from sexual assault samples for DNA analysis using novel polymer filter technology

As submitted by the proposer:

The aim of the proposed project is to address the problem of differential DNA extraction from sexual assault samples, which is a time-consuming, laborious process for many forensic laboratories. In addition, the commonly used standard method for differential extraction frequently results in low quality mixed DNA profiles that are difficult to interpret. In some cases, this method fails to enable generation of a conclusive profile from the male assailant, thereby hampering the criminal justice system’s ability to identify and prosecute offenders.

This proposed project will develop, optimize and validate an efficient differential digest method using novel polymer filters that function as a filtration medium to effectively trap sperm cells while enabling efficient flow through of digested epithelial cell DNA. Preliminary results show that the polymer filters are not clogged by sperm cells, sperm cell recovery from the filter takes place at high efficiency, the resultant sperm fraction profiles are accurate and minimal carry over from epithelial cells is observed. The procedure is simple and highly reproducible, and therefore can be easily implemented in a single-tube format as well as high-throughput, automated workflows using a 96-well plate format. By eliminating the multiple washing and precise pipetting steps required in the standard method, the process of differential digestion is reduced to a series of basic liquid handling steps which can be easily managed by many of the standard robots currently used in crime laboratories.

During this project, the materials and procedure will be optimized for maximized efficiency of sperm cell capture and effective separation from digested non-sperm cell DNA. The method will then be evaluated in comparison to standard methods as well as other commercially available alternatives. In conjunction with the Cuyahoga County Medical Examiner’s Regional Forensic Science Laboratory, the optimized method will be fully evaluated and validated according to the FBI’s Quality Assurance Standards and SWGDAM guidelines.

This work specifically addresses priority areas, including innovative areas of research, identified in the NIJ solicitation. It has the potential to provide a highly efficient and cost-effective alternative to standard differential extraction procedures that can enable forensic laboratories to obtain high quality sperm fraction DNA profiles from a greater percentage of sexual assault cases, thus enhancing the criminal justice system’s ability to identify and prosecute offenders, and facilitating a reduction in the backlog of sexual assault evidence.

This project contains a research and/or development component, as defined in applicable law.

ca/ncf