NCJ Number
214138
Date Published
2006
Length
5 pages
Annotation
This paper describes techniques for obtaining DNA from teeth and from saliva left by bite marks.
Abstract
Recently, a technique called cryogenic grinding was adapted to samples of teeth and bone to enable the DNA present inside the cells to be extracted and purified. This involves the pulverization of the tooth or bone sample in a freezer mill at extremely low temperatures, making it brittle. A plunger moves back and forth inside a sterile tube under the influence of the freezer mill's alternating magnetic field. This forces the sample against a metal anvil at each end of the tube until the tooth or bone sample becomes a fine powder. This increases the surface area sufficiently to allow lysis buffers to break open the cellular and nuclear membranes, which frees genomic DNA into solution. The DNA can be recovered, purified, and submitted to PCR-based DNA analysis. In another area of dental identification, recent studies have shown that salivary DNA of sufficient quality and quantity is deposited during biting and can be recovered from the injury. The DNA from the biter's saliva can be distinguished from the DNA of the victim's skin and compared to known suspect reference samples. In 1995 the author participated in a comprehensive research project that resulted in the development of a new technique for the collection of biological evidence from dried stains. Called the double swab technique, it involves swabbing the salivary stain with a wet swab (sterile, distilled water) under medium pressure, followed by a dry swabbing with light pressure that collects the water left on the skin. Both swabs must be thoroughly air-dried before packaging for submission to the laboratory. 2 figures and 7 references