Hot flakes in cold cases

Abstract

In the past, it was almost impossible for forensic scientists to separate DNA from an undefined number of different individuals in mixed stains where, for example, two or more suspects had handled the same weapon. Such samples often contain complex mixtures with the consequence of ambiguous or inconclusive mixed DNA profiles. Using the method described of comprehensive and/or targeted screening of shed cells adhering to tapings of garments or objects enables such stains to be individualized. To evaluate the method, 500 microscopically selected single skin flakes were analyzed using two different commercial STR kits to compare the success rates for each PCR typing system. The method has been validated for use in routine casework and has been shown to be rapid, sensitive, and reproducible. It can be predicted that many cases in the archives with body tapings, which have not yet been examined will benefit from this new or perhaps more appropriate, reanimated, technical development, and of particular importance are serious crimes, the so-called cold cases. The remarkable forensic value of this simple but time-consuming technique is exemplified by 2 out of approximately 100 cases already successfully solved using this approach.