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Y-STR Profiling in Extended Interval (>3 days) Postcoital Cervicovaginal Samples

NCJ Number
Date Published
March 2008
7 pages
This study tested the ability of commercial and in-house Y-STR systems to provide DNA profiles from victim vaginal samples 3-7 days after a sexual assault occurred.
Profiles were also obtainable 5-6 days post-coitus, although by this stage partial profiles rather than full profiles were a more likely outcome. The DNA profiles from the sperm fraction of a differential lysis were superior to those obtained when a non-differential method was used, in that the allelic signal intensities were generally higher and more balanced; and they exhibited less baseline noise. The incorporation of a simple post-PCR purification process significantly increased the ability to obtain Y-STR profiles, particularly from post-coital samples tested 5 to 6 days after intercourse. An eight-locus Y-STR profile was obtained from a 7-day post-coital sample, which approaches the reported time limit for sperm detection in the cervix. The commercial Y-STR systems tested included the AmpFlSTR Yfiler (Applied Biosystems), PowerPlex Y (Promega), and Y-PLEX 12 (Reliagene) products; and the in-house systems consisted of Multiplex 1 (MPI) and Multiplex B (MPB). Three donor couples were recruited for the study. Post-coital cervical-vaginal swabs (x2) were recovered by each of the three females at specified intervals after sexual intercourse (3-7 days). Each time-point sample was collected after a separate act of sexual intercourse and was preceded by a 7-day abstention period. As a negative control, a pre-coital swab was also recovered prior to coitus for each sampling, and only data from post-coital samples that demonstrated a lack of male DNA in the associated pre-coital sample was used. A number of DNA profile enhancement strategies were used, including sampling by cervical brushing, non-differential DNA extraction methodology, and post-PCR purification. 1 table, 3 figures, and 34 references

Date Published: March 1, 2008