Answer depends more on whether or not the Vampire sparkles in the light of the UV lamp outside my apartment door.

Pretty easy to detect that with even crap tier webcams, they’ll oversaturate glitch or white out.

Then its just a matter of some OpenCV code noticing the sparkles, then dumping the hidden container of holy water on the ceiling on them, and answering the door with a shotgun loaded with an oaken slug.

Next call up John Constantine and see if he knows any rival vampires that have some kind death mark on this particular vampire, or if any of them need a blood meal.

Now you probably have cred with some other vampires so further visits from further vampire cops will at the very least be even more interesting.