Many highly polymorphic minisatellite loci can be detected simultaneously in the human genome by hybridization to probes consisting of tandem repeats of the 'core' sequence. The resulting DNA fingerprints produced by Southern blot hybridization are comprised of multiple hypervariable DNA fragments, show somatic and germline stability and are completely specific to an individual. We now show that this technique can be used for forensic purposes; DNA of high relative molecular mass (Mr) can be isolated from 4-yr-old bloodstains and semen stains made on cotton cloth and digested to produce DNA fingerprints suitable for individual identification. Further, sperm nuclei can be separated from vaginal cellular debris, obtained from semen-contaminated vaginal swabs, enabling positive identification of the male donor/suspect. It is envisaged that DNA fingerprinting will revolutionize forensic biology particularly with regard to the identification of rape suspects.

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 ofpenile swabs. DNA can also beisolatedfromextractsofbuccal swabs. A blind trial involving 4 3 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. Materials and methodsDNA fingerprints were produced as described by Jeffreys et al. [ I , 21. DNA was extracted from whole blood, semen, blood stains, semen stains, hair roots, buccal swabs, and semen-free vaginal swabs by overnight incubation in a sodium dodecyl sulphate (SDS) proteinase K/dithiothreitol (DTT) mixture. Approximately 10 pg of vaginal DNA can be obtained from semen-free vaginal swabs. This quantity of DNA will obscure the presence of sperm DNA from semen-contaminated vaginal swabs; hence it is essential to separate sperm from vaginal cells as previously described [31. Vaginal cells from semen-contaminated swabs were preferentially lysed bv a Dreliminarv incubation in the absence of DTT for 30 Abbreviations: SDS, sodium dodecyl sulphate; Dm, dithiothreitol; kb, kilobase min using the lysG misture. Sperm nuclei were pelleted by centrifugation, washed once with the same mixture, repelleted 0 VCH Verlagsgesellschaft mbH, D-

A computerised system has been used to store DNA profiles from 3 hypervariable loci. This initial survey illustrates that band matching is only possible after analysis of the errors associated with electrophoretic systems. A number of databases have been constructed with the three probes investigated and two methods of frequency determination, 'binning' and 'sliding window' fitting, have been compared.

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Rabbit and mouse spermatozoa from male and female tracts have been examined for their species-antigenic surface character, and for adherent antibodies, by double immunofluorescence techniques. Mouse spermatozoa from the ductus deferens showed an area over the acrosome which was positive to anti-mouse serum that had been absorbed with some male mouse somatic tissues including blood, but those from the uterus and oviduct were not stained. Spermatozoa from the uterus were shown to have an antibody coat on the acrosome, with anti-mouse IgG, but those from the ductus deferens and oviduct did not. Rabbit spermatozoa were more variable but their activity was similar: ejaculated spermatozoa sometimes already had antibody of male origin; the majority of the spermatozoa arriving early in the uterus were coated, but in general those that attained the oviducts were not coated. The results are interpreted as evidence for selection by the female tract of a small antigenically different population; the majority of spermatozoa are rejected and/or destroyed.