Use of PCR for Forensic Analysis of DNA in Cigarette Ends

Abstract

DNA polymorphic sequences can be amplified up to one million fold by the polymerase chain reaction (Mullis and Faloona, 1987). It is possible to characterise minute samples (a single hair, a diploid cell, or single sperm (Higuchi et al., 1988; Li et al., 1988) as long as the target fragment of DNA remains intact. Good results can also be obtained from very old or deteriorated samples, in which DNA is highly degraded (Beroldingen et al., 1989). Due to the remarkable sensitivity of PCR and in spite of its stringent methodology, use of this technique is rapidly becoming widespread in forensic laboratories, among other reasons because it allows cases to be solved in which sample shortage, age or deterioration impede solution by conventional techniques, often inapplicable. With relative frequency cigarette ends are important biological evidence in forensic casework, sometimes the only clue left by a criminal at the scene of the crime. This work presents the results of identification of the individual from traces of saliva left on a cigarette end, in experimental samples and in two forensic cases, using PCR techniques (DQA1, D1S80, DYZ3 for sex determination).