Courts generally don't allow mistake of law as a defence but are there any cases other than insanity where mistake of law is used as a or has been used as a successful defence ?

  • What jurisdiction?
    – o.m.
    Jan 14, 2023 at 14:28
  • 2
    Insanity is not a mistake of law. It is a failure to prove the needed mental state of the accused. Note that is some jurisdictions the verdict is phrased "guilty but insane". Jan 14, 2023 at 14:37

1 Answer 1


In the United States, mistake of law can be an exception for crimes where "willfulness" is an element.

This issue comes up quite often in tax law. If you fail to properly file or pay your taxes because your accountants at Ernst & Young told you the law was something it was not, you haven't violated the law because you reasonably believed you had complied with it.

  • is this the only crime where it's a defense there ?
    – user49663
    May 5, 2023 at 1:10

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