help law enforcement. because they now had the perpetrator's dna profile, but back in the mid-'80s, that wasn't the help it would be today. >> back in 1984, they could at least do a type of blood testing, where they can determine whether or not an individual is a secreteer or a fawn secreteer, basically narrow it down to 20% of the population. >> roughly 80% of americans are secreters, meaning their bodily fluids contain markers for blood type. the other 20% non-secreters don't have those markers. >> the killer was a fawn secreter? >> correct. >> that meant it couldn't be lance, the ex-boyfriend. she said lance threatened her with a knife. blood tests revealed he was a secreteer. heed a anal by putting him 300