Clinical forensic sample collection techniques following consensual intercourse in volunteers - cervical canal brush compared to conventional swabs.

The purpose of the research was to evaluate gynecological evidence collection techniques; the benefit of cervical canal brush sample compared to vaginal fornix and cervical swab samples and the time frame for detecting Y-chromosomal material QiAmp DNA Mini Kit(®) and Quantifiler Y Human Male DNA Quantification Kit(®) in adult volunteers following consensual intercourse. Eighty-four adult female volunteers following consensual intercourse were recruited for the study. By combining all sample collecting techniques, 81.0% of the volunteers were Y-DNA positive. Up to 60 h the conventional swab sampling techniques detected more Y-DNA positive samples when compared to the brush technique. However, after 60 h, the cervical canal brush sample technique showed its benefit by detecting 27.3% (6/22) of Y-DNA positive samples, which were Y-DNA negative in both conventional swab sampling techniques. By combining swab and brush techniques, 75% of the volunteers were still Y-DNA positive in 72-144 post-coital hours. The rate of measurable Y-DNA decreased approximately 3% per hour. Despite reported consensual intercourse, 6.8% (3/44) of volunteers were Y-DNA negative within 48 h. Y-DNA was not detected after 144 post-coital hours (6 days). In conclusion, the brush as a forensic evidence collection method may provide additional biological trace evidence from the cervical canal, although the best biological trace evidence collection can be obtained by combining all three sampling techniques. The time frame for gynecological forensic evidence sample collection should be considered to be at least a week if sexual violence is suspected.