Spots left on material by the products of male ejaculation. After someone has masturbated and successfully ejaculated, he may leave the semen in his underwear. This will cause a stain, known as a...
As far as I know... REAL blacklights will detect any trace of a mammal.... hair, urine, vomit, feces, and... sperm!! just make sure the room is as dark as you can get it and shine that light around...
