Anybody who frequents prostitutes would be wise to carry a nice video camera, a tripod, and some lights in the back of their car. Then, if they get busted, just claim it's all part of a porn film, and/or a documentary about prostitution. Even the prostitute, who may be unaware of your "scam", would be wise to go along with it and confirm to the cop that she is indeed taking part in the video production.