Interpretation of Gm Testing Results: Two Case Histories

Abstract

Two cases in which bloodstains and seminal stain evidence were important were subjected to the identification of Gm antigenic determinants. In the first case, the identification of the seminal stain showed the absence of Gm 1 and 12 determinants and the presence of Gm 4. The interpretation of these results would on the surface suggest that the seminal evidence came from one of two suspects. However, since the absence of Gm 12, which occurs on the immunoglobulin G (IgG) 3 subclass, was not confirmed by the demonstration of another IgG 3 subclass Gm antigenic determinant this result was inconclusive. In the second case, bloodstain and seminal fluid evidence showed that seminal fluid identified on the victim's nightgown had Gm antigenic determinants consistent with those of the suspect and also that blood on the suspect's underpants had Gm antigenic determinants consistent with the deceased's blood. The results of these two cases are interpreted with regard to the Gm results obtained.