MODEL PENAL CODE
(1) Mistake as to Age. Whenever in this Article the criminality of conduct depends on a child's being below the age of 10, it is no defense that the actor did not know the child's age, or reasonably believed the child to be older than 10. When criminality depends on the child's being below a critical age other than 10, it is a defense for the actor to prove by a preponderance of the evidence that he reasonably believed the child to be above the critical age.
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