§ 562.031 – Ignorance or Mistake as a Defense in Missouri Criminal Law

562.031. Ignorance and mistake.

Not knowing the law usually isn’t a valid excuse.

Just because someone didn’t know something was illegal—or misunderstood a fact—doesn’t mean they’re off the hook, unless that mistake affects their intent or was reasonably based on bad legal info.

1. A person is still responsible for a crime even if they were mistaken about a fact or the law—unless that mistake means they didn’t have the intent the crime requires.

2. A person isn’t off the hook for thinking what they did wasn’t a crime—unless that belief is reasonable and:

1. The crime comes from a regulation they didn’t know about, wasn’t made public, and they couldn’t have learned about it by being reasonably careful; or
2. They reasonably relied on a legal source that turned out to be wrong, such as:
   • A law (statute);
   • A court decision;
   • An official interpretation from a proper government agency or official.

3. It’s the defendant’s responsibility to raise the issue of whether they reasonably believed their actions weren’t illegal under the rules above.

View the full statute here

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