PCR-BASED DNA TYPING OF SALIVA ON STAMPS AND ENVELOPES

In forensic cases involving mail bombs, extortion, kidnapping or threa tening letters, biological evidence such as the saliva used to attach the stamp and seal the envelope could be used for genetic analysis. We have developed a highly sensitive semi-nested PCR method for the HLA- DRBI focus, suitable for the analyses of very limited amounts of DNA. When applied to a set of stamps and envelopes with saliva from control individuals, typing results we, e consistent with those obtained risi ng hairs drawn from the same individuals. No interference was found du e to DNA from the fingerprints of people handling the letters. The sys tem was applied to three forensic cases with threatening letters. The first case resulted in an exclusion of the suspect. In the second case , the suspect could not be excluded (probability of identical genotype by chance >0.01). These results demonstrate that biological evidence in cases with threatening fetters is amenable to genetic typing.