ISSN: 0022-1198
CODEN: JFSCA
Page Count: 5

PCR-Based DNA Typing of Saliva Stains Recovered from Human Skin
Valenzuela, A
University of Granada, Faculty of Medicine,

Sweet, D
University of British Columbia, Faculty of Dentistry,

Villanueva, E
University of Granada, Faculty of Medicine,

Lorente, JA
University of Granada, Faculty of Medicine,

Lorente, M
University of Granada, Faculty of Medicine,

(Received 28 March 1996; accepted 16 September 1996)

Abstract

Human bites in cases of homicide, sexual assault, and abuse are often distorted due to the elasticity and curvature of the skin. Physical comparison of a bite mark to a suspect's teeth is sometimes difficult. Saliva, which is usually deposited during biting, can be collected and analyzed to identify the perpetrator. Using simulated bite mark situations in two experimental series, three samples of 40 μL of whole saliva were deposited on the skin of 27 cadavers (at 33 sites) and three samples of 100 μL of whole saliva were deposited on the skin of 5 cadavers (at 12 sites). Saliva was collected using the double swab technique at t = 5 min, t = 24 h, and t = 48 h. DNA was extracted using the modified Chelex method and submitted to PCR-based typing at two short tandem repeat loci. Results indicate that the concentration of DNA in saliva recovered from skin varies as a function of time since deposition. There is a significant decrease in concentration in the first 24 h but the concentration remains stable from 24 to 48 h. The success of PCR amplification is independent of the time since deposition or the concentration of DNA in the saliva sample. Contamination from the DNA of the cadaver was not found in any of the cases studied.

Keywords:
forensic science, DNA typing, forensic odontology, saliva, polymerase chain reaction, HLA-DQA1, HUMTH01, HUMVWA, short tandem repeats

Paper ID: JFS14146J
DOI: 10.1520/JFS14146J
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