A review of DNA profiling success for laser microdissected forensic casework samples

ABSTRACT

Laser microdissection (LMD) is a tool that is used in forensic laboratories for the analysis of DNA from specifically targeted cells. Since 2010, the Institute of Environmental Science and Research Limited’s (ESR) Forensic Biology laboratory has applied LMD DNA testing to a variety of sexual assault casework samples where small numbers of sperm are present in cell mixtures. In this paper we review the DNA profiling results obtained from semen-stained casework samples that have been analysed using the LMD DNA methodology developed in our laboratory. Dissected sperm have been analysed using the AmpFISTR Identifiler amplification kit at 28 cycle PCR, the AmpFISTR MiniFiler amplification kit at 30 cycle PCR, or the AmpFISTR SGM Plus amplification kit at 34 cycle PCR, depending on the number of sperm recovered and on consideration of other circumstantial case information, such as the time since intercourse (TSI). From a review of these data, success rates for different sample numbers of sperm recovered from semen-stained samples are determined. The DNA profiling results obtained from three cases where laser microdissection has been used are also presented to demonstrate the success of the LMD testing strategy in a forensic laboratory.