Mistake of law is a viable exemption in those instances where an individual demonstrates an effort to learn what the law is, relies on the validity of that law and, later, it is determined that there was a mistake in the law itself.
A Federal corrections officer was arrested in a Manhattan social club for possession of a loaded .38 caliber automatic pistol. As his defense, he claimed he mistakenly believed he was entitled to carry a handgun without a permit as a peace officer and was excused from criminal liability under the mistake of law statute. The trial court convicted the peace office and on appeal, the appellate division upheld the conviction. The case was appealed to the Court of Appeals of New York.
Should the court have considered the defence of mistake of law?
The Court held that a mistake of law does not excuse the commission of prohibited acts. The rule on the subject appears to be, that in acts mala in se, the intent governs, but in those mala prohibita, the only inquiry is, has the law been violated? It further concluded that the correctly construed view of the defense of mistake or ignorance should not be recognized except where specific intent was an element of the offense or where the mistakenly-relied-upon law was subsequently adjudicated as incorrect. The court determined that such a rule would ensure procedural due process under constitutionally vague statutes, yet not permit the exception to swallow the rule. The forbidden act of possessing a weapon was clear and unambiguous, and the court determined that the defense of mistake did not apply to the situation because the only mistake was in defendant's understanding.