Threat mail and forensic science: DNA profiling from items of evidence after treatment with DFO

Two cases of threatening letters with their accompanying envelopes were received to the Division of Forensic Identification unit of the Israel Police. The envelopes, including the stamps, and the letters were initially examined for latent fingerprints by the DFO reagent, known to cause degradation of DNA. Although no latent fingerprints could be visualized on any of the items, the biology laboratory using organic DNA extraction, was successful in defining genetic profiles from all the items employing six STR loci, even after treatment with DFO. In a controlled experiment, a known donor attached a stamp, by licking, to an envelope. This item was treated with DFO and then profiled using STR loci. The results showed that previous DFO treatment on the control stamp before DNA analysis had no negative effects on obtaining the DNA profile of the known donor using STR loci.