REFERENCE:Sweet D, Lorente M, Lorente JA, Valenzuela A, Villanueva E. An improved method to recover saliva from human skin: The double swab technique. J Forensic Sci 1997;42(2): 320-322. ABSTRACT:Human bite mark evidence is often found in violent crimes. Due to the difficulties of physically comparing an injury site on elastic and curved skin surfaces to the teeth of a suspect, the authors have considered using salivary DNA evidence to identify the bite perpetrator. Several techniques were evaluated to determine the best method of recovering saliva from human skin before extracting genomic DNA from the collection substrate. A classical stain recovery technique using a wet cotton swab was tested against one utilizing a wet filter paper. Additionally, a new method, referred to as the double swab technique, using a wet cotton swab followed by a dry cotton swab was also evaluated. After recovering a dlied saliva stain, DNA was extracted using the modified Chelex method, quantified using the slot-blot procedure, and amplified at three polymorphic loci. The double swab technique showed the highest percentage recovery of saliva from human skin among the three methods studied. This technique is suggested as an improvement over the classical single wet cotton swab technique.KEYWORDS: forensic science, saliva, bite marks, odontology, serology, forensic evidence Teeth are often used as a weapon in violent crimes when one person attacks another, or in self-defense against an attacker (1). Human bite marks are found in cases of homicide, sexual assault, and crimes of family violence including child and spousal abuse (2). Conventional analysis strategies attempt to physically compare the injury pattern found on the victim's skin to the teeth of the suspected biter to reach conclusions regarding relative concordance (3).In addition to considering bite marks as examples of physical evidence, the authors have also focused their attention on bite ~Forensic odontologist, UBC Faculty of Dentistry, Vancouver, BC Canada.2Assistant professor, associate professors, and professor, respectively, Faculty of Medicine, University of Granada, Spain.This project was supported by grants from the Ministry of Education and Science of the Government of Spain (PB93-1155), the Plan Propio de Investigaci6n of the University of Granada, Spain, and by the Dentistry Canada Fund/Warner Lambert Foundation, Ottawa, Canada.Received 3 June 1996; and in revised form 31 July 1996; accepted on 2 Aug. 1996. marks as biological evidence. It is assumed that forensically significant amounts of saliva are deposited during biting, sucking, or licking and that traces of salivary evidence can be recovered for identity testing.Determination of the origin of a saliva stain using conventional markers is not highly sensitive nor discriminatory. The limited detectability of blood group antigens and polymorphic proteins due to their low concentrations is an inherent problem (4). Genomic DNA testing has increased sensitivity compared with conventional saliva testing methods ...

The reference database of highly informative Y-chromosomal short tandem repeat (STR) haplotypes (YHRD), available online at http://ystr.charite.de, represents the largest collection of male-speci®c genetic pro®les currently available for European populations. By September 2000, YHRD contained 4688 9-locus (so-called``minimal'') haplotypes, 40% of which have been extended further to include two additional loci. Establishment of YHRD has been facilitated by the joint efforts of 31 forensic and anthropological institutions. All contributing laboratories have agreed to standardize their Y-STR haplotyping protocols and to participate in a quality assurance exercise prior to the inclusion of any data. In view of its collaborative character, and in order to put YHRD to its intended use, viz. the support of forensic caseworkers in their routine decisionmaking process, the database has been made publicly available via the Internet in February 2000. Online searches for complete or partial Y-STR haplotypes from evidentiary or non-probative material can be performed on a non-commercial basis, and yield observed haplotype counts as well as extrapolated population frequency estimates. In addition, the YHRD website provides information about the quality control test, genotyping protocols, haplotype formats and informativity, population genetic analysis, literature references, and a list of contact addresses of the contributing laboratories. #

Supplemental Digital Content is available in the text

No 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.