A sequence of tests of minute human blood stains for human origin identification and ABO blood grouping

A series of examinations is presented for human origin identification and ABO blood grouping of doubtful minute human blood stains. A blood-stained thread (0.5 cm in length) was first tested to identify human origin by microprecipitation method and then the ABO blood type was determined by both a modified absorption-elution test and a modified mixed agglutination. In the continuous tests, the maximum limits of positive reactions of the microprecipitation method, the modified absorption-elution test, and the modified mixed agglutination were 1:640, 1:160, and 1:2,560 diluted blood, respectively. A and B agglutinogens were more sensitively determined than H agglutinogen. Hemagglutinogens of blood stains on cotton threads were more easily detected than those of polyester ones.