They'll also use Thermal Imaging Cameras much like Fire Fighters do scanning the outside of the house to see rooms that have a higher amount of heat from lamps with a warrant of course.
I've had police knock on my door twice after doing flyovers of the area using FLIR, and after looking at our electric bill. Ask me politely if they could inspect the premises, and were a phone call away from procuring a warrant. I've been aware that this happens with large coral tanks in private residences, so I said "Go for it." They walked into my living room, and saw the 180 gallon reef tank that is built into 6 feet (4 metal halide bulbs @250 watts each, plus another 500 watts of power compacts) of my living room wall, oogled at my fish and corals, for 15 minutes, and turned around and walked out the door.
Why they had to do it twice, is beyond me. Guess they liked my corals.