NCJ Number
172050
Journal
Journal of Forensic Sciences Volume: 42 Issue: 3 Dated: (May 1997) Pages: 447-451
Date Published
1997
Length
5 pages
Annotation
Results presented show that saliva trace evidence recovered from human skin contains forensically significant quantities of DNA that are stable during the postmortem interval over a reasonable period of time.
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 ml of whole saliva were deposited on the skin of 27 cadavers at 33 sites and three samples of 100 ml of whole saliva were deposited on the skin of 5 cadavers at 12 sites. Saliva was collected by using the double swab technique at 5 mins., 24 hours, and 48 hours. DNA was extracted by using the modified Chelex method and submitted to PCR-based typing at two short tandem repeat loci. Results show 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 hours, but the concentration remains stable from 24 to 48 hours. 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. 1 figure, 1 table, and 35 references