A Subway in Knoxville, Tennessee has a new deterrent for criminals: a face full of DNA. As a test program, the store has installed a box that sprays the robber in the face as they run out of the store. The DNA can't be washed off and will only appear under black light. So if you're in Knoxville at a goth club and you see some with a big purple splatter on their forehead, they're probably rolling in Subway Rewards Cards.