Quantitative analysis of species identification tests of bloodstains using anti-human serum

Immunological reactions of bloodstains of human and animals to anti-human serum were analysed quantitatively to determine which technique is the most effective to differentiate human bloodstains from those of animals. The lower threshold of counter-electrophoresis was 10-25 micrograms protein/ml and increased only slightly with increasing age of the bloodstains, while that of the ring test and immunodiffusion decreased greatly. In counter-electrophoresis, absorption of anti-human serum by Japanese monkey serum resulted in a marked decrease in the cross reaction with animals, and still showed no change in the lower threshold for human samples. The present results show that counter-electrophoresis is especially useful for the identification of human bloodstains.