THIS !!!
"Do as we say or we will leave your DNA at the next murder victim."
Imagine a crime scene, and on the gun we find DNA >>big trouble for the person with same DNA, even if innocent.
Clearly, most of all if the poor guy has been manipulated in order to be closed to the crime scene (recording of phones calls in the same area) and if he was with someone who will disappear just after. Much more efficient than a sex video that can be manipulated with modern softwares.
Maybe to extract stem cells to accelerate the growth
All this is terrifying, but unfortunately I think it's in the mind of some crazy people.