Research report submitted by the National Center for Forensic Science to the U.S. Department of Justice, National Institute of justice, Award Number: 2007-DN-BX-K148. Ficheiro de 2,08 MB em formato PDF (61 p.).

The ability to obtain an autosomal STR profile of the semen donor from a living victim rapidly diminishes as the post-coital interval is extended. This is of particular concern in those instances where victims of sexual assault provide vaginal samples several days after the incident. In an attempt to overcome the technological impediments of typing success with these samples, we previously employed the use of Y chromosome STR profiling which, by specifically targeting only the male DNA in the sample, can reduce or even eliminate the possibility of male profiling masking or critical PCR reagent titration due to the presence of an overwhelming amount of female DNA. Using Y-STR profiling and additional strategies such as cervical sampling and post-PCR purification, we were able to obtain Y-STR profiles from samples collected 5-6 days after intercourse. However, the reproductive biology literature demonstrates the presence of several spermatozoa in the human cervix up to 7-10 days post coitus. The question thus arises as to why, even with improved extraction and profiling techniques, we still fail to routinely recover profiles from samples collected >6 days after intercourse. Thus the aim of the current work was to develop novel strategies to permit the recovery of male donor DNA profiles from extended interval post-coital samples (> 6 days). Using a combination of novel methods to selectively enhance male DNA fractions, we demonstrate the ability to obtain male donor profiles in extended interval post-coital samples collected 6 to 9 days after intercourse. This represents a significant improvement in the time frame in which male profiles can besuccessfully recovered from post-coital samples.