DNA extraction from human saliva deposited on skin and its use in forensic identification procedures

Abstract

Saliva is usually deposited in bite marks found in many homicides, assault and other criminal cases. In the present study, saliva obtained from volunteers was deposited on skin and recovered for DNA extraction and typing in order to evaluate its usefulness for practical case investigation and discuss the contribution of forensic dentistry to saliva DNA typing. Twenty saliva samples were colleted from different donors and used as suspects' samples. Five of these samples were randomly selected and deposited (250 µl) on arm skin. Saliva was collected from skin using the double swab technique. DNA from saliva and skin-deposited saliva samples was extracted by the phenol-chloroform method. DNA samples were amplified by PCR for DNA typing using a set of 15 STRs. The recovery of DNA from saliva deposited in the skin was 14 to 10 times lower than DNA quantity from saliva samples. DNA typing was demonstrated in 4 of 5 deposited saliva samples, the likelihood ratios estimated for these samples based on data of the Brazilian population were 1:11, 1:500, 1:159.140 and 1:153.700.123. Our results indicate that standardized procedures used for DNA collection and extraction from skin-deposited saliva can be used as a method to recover salivary DNA in criminal cases. However, it is important to observe that DNA recovery in forensic samples can be difficult. This study suggests that the analysis of saliva deposited on skin be incorporated into a criminal investigation since it may have great discriminatory power. DESCRIPTORS: DNA; Forensic dentistry; Saliva. RESUMO:A saliva é usualmente depositada em marcas de mordida encontradas em homicídios, agressões e outros crimes. Neste estudo, a saliva obtida de voluntários foi depositada na pele, recuperada para extração e tipagem do DNA, para avaliação de sua utilização e sua contribuição na odontologia legal. Vinte amostras de saliva foram coletadas de diferentes doadores e utilizadas como amostras de suspeitos. Cinco dessas amostras foram sorteadas e depositadas (250 µl) na pele. A saliva foi coletada da pele usando-se a técnica do duplo esfregaço. O DNA da saliva e das amostras de saliva depositadas sobre a pele foi extraído pelo método fenol-clorofórmio. As amostras de DNA foram amplificadas por PCR para a tipagem do DNA usando-se um grupo de 15 STRs. O DNA recuperado da saliva depositada na pele foi de 14 a 10 vezes menor que o DNA das 20 amostras de saliva. O perfil do DNA foi demonstrado em 4 de 5 amostras de saliva depositadas, e a razão de verossimilhança das amostras baseada em dados da população brasileira foi 1:11, 1:500, 1:159,140 e 1:153,700,123. Nossos resultados indicam que procedimentos padronizados utilizados para coleta e extração de DNA de saliva depositada podem ser utilizados como um método para recuperar DNA de saliva em casos forenses; entretanto, é importante observar que amostras forenses podem apresentar problemas na recuperação do DNA em quantidades adequadas. Este estudo sugere que a análise de saliva depositada sobre a pele pode ser incorporada ao...

PCR detection of multiple human herpesvirus DNA in saliva from HIV-infected individuals in Teresina, State of Piauí, Brazil

“…DNA from 1.5ml of each saliva specimen was centrifuged and the DNA was isolated from the cell pellet using the phenol-chloroform method described by Anzai-Kanto et al 16 . Two microliters of DNA were used in each PCR reaction.…”

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

“…The amount of saliva deposited on the skin is usually very small in bite marks; in addition, environmental factors, such as heat, bacteria, moisture, and mold, can render the DNA unusable (Wick, 2000). Partial profiles were obtained even under controlled experimental conditions, wherein the saliva was placed on the skin of volunteers (Anzai-Kanto et al, 2005).…”

“…Previous experimental studies have shown that the double-swab technique allowed for the identification of pure DNA profiles (Sweet et al, 1997a,b;Anzai-Kanto et al, 2005). However, the use of the single swab technique may be more appropriate in actual cases, wherein the skin surface is disrupted and the sample might be contaminated with the DNA of the victim.…”

“…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.…”

Term Forensic Odontology

“…In modern days with development of technology application of the knowledge of dental and paradental knowledge helps in solving many legal issues in civil and criminal matters [4][5][6].…”