"that's a real popular rumor about cops having to identify themselves as such if you ask them a straight-out question. But that's all it is--a rumor."

I'm guessing that rumor started with the Movie 'Blow' when Pee Wee Herman asked Johnny Depp if he was a cop, and he had to tell him or it was entrapment. Just a guess-I remember taking note of it and wondering if it was true.