"Are you a cop??"

I was watching some police show like Cops the other day and I was amazed at how many criminals would ask “are you a cop?” to the undercover officer, and when they received a no they would be perfectly satisified that they were receiving a truthful answer.

Was it ever mandatory for undercover police officers to answer this question truthfully? It seems to me that this is a wide held belief in a lot of places. Is it necessary for police to answer this question truthfully anywhere??? Where did this rumour come from?

I don’t know the origin or whether it was ever true but the question has come up at least one before here, and the consensus (including cops) was that it’s bullshit.

It’s just one of those silly urban legends. If you are not under arrest, they can lie all that they want.

Didn’t Cecil or a Science Advisory Board member have a column on this?

Some people mistake a police officer lying as tantamount to entrapment. In this case, it wouldn’t be.

They can lie all they want during an interrogation, period. Whether you are under arrest or not is immaterial.

They can lie to you all they want (or nearly so) when you are under arrest as well. For instance, one classic interrogation strategy is to confront a suspect with a fictitious co-conspirator confession. (E.g., “Joe, you better fess up now. Your buddy Mike is in the next room and he’s already spilled the beans.” But Mike’s not in the next room and he hasn’t spilled the beans.)

As to the OP, an undercover cop does not have to tell the truth about his or her identity. That said, asking the question gives the would-be criminal a chance to measure the undercover cop’s reaction and assess his or her credibility. I suppose if I were in that position, I’d ask just to see how the person responded. Some undercover cops are better than others.

Or more commonly, Mike is in the next room being as recalcitrant as Joe, but the cops are feeding him the same line, hoping one (or both) will roll over on the other.

IOW, “The Prisoner’s Dillema”, the fodder of many an intro-to-game-theory class. The best solution is for both criminals to stick to their stories and go free, the next best is for both to turn their buddy in and get a reduced sentence, and the worst is for one guy to keep his mouth shut, the other to turn him in, and he gets a lengthy sentence.

Seems that, fairly often, the criminals don’t find eachother to be terribly turstworthy, and turn eachother in.

FRAZIER v. CUPP, 394 U.S. 731 (1969)

Didn’t cecil cover this? I can’t find it.

The dilemma comes from the fact that the situation is constructed so that each person maximizes their own outcome by screwing over the other guy, regardless of what the other guy does. Although the best joint outcome comes from both players cooperating with each other, this outcome is extremely difficult to achieve in practice for any finite situation.

Ohhh… I never quite got the “regardless of what the other guy does” bit. I always assumed it was just a parable about the lack of trust amongst criminals.
Maybe this is why I failed Intro to Game Theory :confused:

A quick search turned up this thread, among others. Cited in that thread is this Snopes piece on the subject. But, AFAICT, neither The Master nor the SDStaff have addressed the issue. Yes, the theory is entrapment and, no, it’s not correct.

Two more articles, here and here. Interestingly, no one cites any case law on this precise question (as distinguished from the general parameters of entrapment), nor have I found any. Which suggests that, while the “principle” is common knowledge among lay people, defense attorneys know better than even to hazard the argument.

I can’t provide any appellate court cites; I’ve been involved in a number of these cases, and in at least a couple the issue was brought up by the defense (grasping at straws, perhaps), but the resulting convictions were never appealed nor was I ever asked to testify one way or the other as to my response.