An evaluation of DNA fingerprinting for forensic purposes

Many highly polymorphic minisatellite loci can be detected simultaneously in the human genome by hybridisation to probes consisting of tandem repeats of the ‘core’ sequence. The resulting DNA fingerprints produced by Southern blot hybridisation are comprised of multiple hypervariable DNA fragments, show somatic and germline stability and are completely specific to an individual. DNA of high molecular weight can be isolated from blood and semen stains up to 4 years old. Sperm nuclei can be separated from vaginal debris and the sperm DNA examined in isolation, allowing the positive identification of rapists. Correspondingly, vaginal DNA can be isolated from extracts of penile swabs. DNA can also be isolated from extracts of buccal swabs. A blind trial involving 43 blood samples, 11 bloodstains and 11 semen stains has been successfully carried out. It is envisaged that genetic fingerprinting will shortly form an important part of casework procedure in forensic science laboratories.