NCJ Number
227520
Journal
Law and Order Volume: 57 Issue: 6 Dated: June 2009 Pages: 36-38,40-41,43
Date Published
June 2009
Length
6 pages
Annotation
This article instructs police officers who may be involved in a "cold" case investigation in the state-of-the-art of DNA technology, so investigators may have the information to determine whether evidence items from a cold case would qualify for retesting under current methods of DNA analysis.
Abstract
DNA analysis was first used to solve a crime in 1986. At that time, it was necessary to obtain a relatively large sample of evidence for DNA testing, and the sample was often used up in testing with the older DNA testing, called Restriction Fragment Length Polymorphism (RFLP). With newer techniques, RFLP is no longer used because of its limitations. Current DNA testing is anchored by Short Tandem Repeat (STR) technology, which is part of a larger type of analysis that involves polymerase chain reaction (PCR). PCR can make millions of exact copies of DNA from a biological sample. This DNA amplification allows DNA analysis to be conducted on biological samples as small as a few skin cells. DNA technology that further refines STR is imminent. Mini-filer or mini-STR is being used for testing previously untestable DNA samples, and it looks at one to three loci, or locations, on the DNA strand. Being able to test for even 1 location at a time instead of all 13 loci on the DNA strand has allowed minute or degraded DNA samples to yield results. YSTR or Y-chromosome analysis is useful in testing for only male or female DNA, which is often the case in sexual assault cases or missing persons cases. Mitochondrial DNA (mtDNA) analysis can be used to examine the DNA from samples that cannot be analyzed using STR. Although older biological samples that lack nucleated cellular materials - such as hair, bones, and teeth - cannot be analyzed with STR, they can be analyzed with mtDNA.