In Schneeberger's case, it seems that he was simply infusing a part of his body with another man's blood and then making sure that the lab tech drawing the bloo

In Schneeberger's case, it seems that he was simply infusing a part of his body with another man's blood and then making sure that the lab tech drawing the blood sample drew it from the same place. Once they tested his hair and saliva, they had a positive match.