Assessment of DNA and mtDNA Degradation in Sperm Cells Collected by Laser Micro-dissection

Sexual assault samples are among the most frequently analyzed in a forensic laboratory. These accounts for almost half of all samples processed routinely and a large portion of these cases remain unsolved. These samples often pose problems to traditional analytic methods of identification because they consist most frequently of cell mixtures from at least two contributors: the victim (usually female) and the perpetrator (usually male). In this study we prepared simulated sexual assault samples and conducted amplification and DNA genotyping from sperm cells collected with laser microdissection at different time intervals to assess the DNA degradation at those intervals. Furthermore, we then investigated the possibility of recovering mtDNA from the collected sperm cells, particularly in cases where autosomal DNA was not suitably amplified. With this work we determined that it becomes possible to extend the timeframe for performing an analysis, by researching other sources of DNA, namely mtDNA.