The Recovery and Persistence of Salivary DNA on Human Skin

Abstract

Salivary DNA is encountered in many crimes, such as sexual assaults and murders. In this study, saliva from three male donors was deposited on the skin of three female recipients. The amount of male salivary DNA remaining on the female skin was measured over a 96-h period using the Quantifiler™ Y Human Male DNA Quantification Kit. In eight of the nine experiments, a full male DNA profile matching the donor was obtained even after 96 h. In addition, the study showed that the concentration of salivary DNA varied from donor to donor and from day to day. The efficiency of two recovery methods, wet and dry swabbing and minitaping, was compared. The results indicate the tapelift method gave higher DNA recovery. This study also examined the secondary transfer of salivary DNA from skin to fabrics. Cotton and polyester give higher DNA transfer than leather.

Forensic Genetics and Genotyping

“…Kenna et al have reported that salivary DNA persists on the skin a minimum of 96 h (19). For example, it is possible to extract DNA from bite marks within this period, but amount of saliva deposited on the skin is usually very small in bite marks (19,20). In addition, the concentration of salivary DNA varied from donor to donor and from day to day (19).…”

“…The gene that codes for an exacting protein contributes to only 2-5% of DNA, whereas the remaining 95% are non-coding DNA (25). Therefore we mark them as markers (19). However, some of these noncoding markers are linked with visible traits (3).…”

“…Saliva can also be placed on human skin through kissing, biting, sucking and licking. Kenna et al have reported that salivary DNA persists on the skin a minimum of 96 h (19). For example, it is possible to extract DNA from bite marks within this period, but amount of saliva deposited on the skin is usually very small in bite marks (19,20).…”

“…For example, it is possible to extract DNA from bite marks within this period, but amount of saliva deposited on the skin is usually very small in bite marks (19,20). In addition, the concentration of salivary DNA varied from donor to donor and from day to day (19). Also many factors can cause DNA damage in saliva, such as: diet, brushing habits, eating habits, smoking, cancer in the oral cavity, fungal infection, etc.…”

Relevance of sampling and DNA extraction techniques for the analysis of salivary evidence from bite marks: a case report

“…Studies conducted under controlled laboratory conditions have indicated that the DNA analysis of saliva placed on the skin of volunteers or cadavers may help in the identification of individuals (Sweet et al, 1997a;Anzai-Kanto et al, 2005;Kenna et al, 2011). However, the application of this approach to an actual criminal case has been reported only once before in forensic literature.…”