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Bacterial Contamination in a Mixed Semen-Vaginal Sample From a Sexual Assault-Murder Case

NCJ Number
163581
Journal
Canadian Society of Forensic Science Journal Volume: 29 Issue: 1 Dated: (March 1996) Pages: 21-28
Author(s)
D Michaud; P Gagnon
Date Published
1996
Length
8 pages
Annotation
In 1991, a case was received at the Royal Canadian Mounted Police's Central Forensic Laboratory in which a young woman was sexually assaulted and murdered.
Abstract
Vaginal samples taken during the autopsy were submitted by police, along with comparison samples from the deceased, her boyfriend, and a suspect. While performing semen identification tests, substantial microbial contamination was noticed in the vaginal samples. The DNA profile from the epithelial fraction showed a mixture consistent with the deceased and three other unexplained fragments. The sperm cell fraction, which did not show any bacterial contamination, was the forensically important sample. Sample fractions are characterized, and suggestions are offered to help forensic biologists recognize the occurrence of microbial contamination in a human DNA profile. 19 references, 1 table, and 2 figures