I can just see it now (theoretically, that is): The police launch a drone which is equipped with some kind of firearm, as well as with a hi-def camera (zoom lens, of course), and...... facial-recognition software. Said drone flies around over the city, then spots a "suspect", checks him/her against a database of known criminals, finds out the perp is wanted, then fires away with a tranquilizer round. It then notifies the ground troops as to where the perp is. The "perp" turns out to be a close look-alike to the real criminal.... and, to top things off, the individual succumbs to the tranquilizer's concoction. .
Can you say "Hello lawsuit?"