Species identification of blood stains using a biotin-labeled DNA probe

In an attempt to identify blood stains of human origin, DNA was extracted from human and animal dried blood stains and examined using recombinant DNA techniques. As a DNA probe, biotin-labeled or radioisotopically labeled human repetitive sequence 2.3 Kb Hind III fragment (pH 12) in pBR 322 was used. The probe clearly hybridized with human DNA, but not with DNA extracted from frog, fish, mouse, rat, rabbit, chicken, cat, dog, and sheep. DNA from a Japanese monkeies and from a chimpanzee also hybridized with comparable efficiency. The minimum amount of the blood for the species identification was estimated to 0.4 microliter of fresh blood, 2.1 microliters of 2 weeks old blood stain and 3.8 microliters of 3 months old blood stains, indicating that only one drop of human blood is sufficient for species identification. There was no difference of "signal" between isotopic and non-isotopic procedures for DNA analysis. The advantages of the non-isotopic method for species identification of blood stains in forensic science is briefly discussed.