It's been established that police in the US have pretty broad discretion in terms of being permitted to lie. If you ask an on-duty police officer if something is legal, can they lie about that?

I know there is a previous question that asked "Can the police lie about whether I am compelled to do something?" but I am asking "Can the police lie about whether I am permitted to do something?"

For example, say you're visiting a state where you're unfamiliar with local laws, and by some strange coincidence there is someone giving marijuana samples, but there is also a police officer nearby. If you ask the officer, "Is it legal to have small amounts of marijuana here?" could the officer say "It's fine. Go for it!" but then arrest you anyway?

Note, I do not use marijuana. That just seemed like the clearest example of something where laws vary greatly from state to state.

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    Are you asking whether the police officer could be found criminally or civilly liable for lying to you? Or do you want to know whether the officer's lie could be used successfully in your defense?
    – phoog
    Nov 27, 2020 at 20:42
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    I'm asking if it could be used in your defense.
    – SegNerd
    Nov 27, 2020 at 20:46
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    There is a fairly recent SCOTUS case (maybe two to five years ago) on a closely point, involving a traffic violation related to the state of repair of a vehicle that a cop misinterpreted. I don't have time to dig it up right now.
    – ohwilleke
    Jan 21, 2021 at 19:53

1 Answer 1


There is no clear rule on this matter, but there is a reasonable prospect for using an entrapment defense in this case, when deliberate deception is employed.

There are two tests for entrapment: the subjective test and the objective test. The former focuses on the defendant's state of mind: whether the defendant is predisposed to commit the crime without law enforcement pressure. The latter is where the officer uses tactics that would induce a reasonable, law-abiding person to commit the crime.

It depends in part whether the jurisdiction recognizes one of these defenses. An example of objective entrapment: "A reasonable, law-abiding person could be tempted into committing prostitution for a substantial sum of money like $10,000." Similarly, applicable to this question: A reasonable, law-abiding person could be tempted to undertake a pleasurable action having been assured that the action is actually legal.

Where the subjective test applies: The fact of asking about the legality of an action is evidence that the defendant was not predisposed to commit the crime.

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