Blood grouping in a sexual assault case: criteria and methodolgy for genetic marker analysis

A sexual assault case was received in the laboratory. Upon examination, a small bloodstain was located on a bed sheet that was recovered from the defendant's motel room. Typing the whole blood samples from the defendant and the victim revealed that both blood samples exhibited identical phenotypes in eleven different genetic markers. Gm(1) and Gm(2) analysis was then performed on the two whole blood samples which provided discrimination between the two parties.