N.Y. Penal Law § 15.20

§ 15.20 Effect of ignorance or mistake upon liability.\n 1. A person is not relieved of criminal liability for conduct because\nhe engages in such conduct under a mistaken belief of fact, unless:\n (a) Such factual mistake negatives the culpable mental state required\nfor the commission of an offense; or\n (b) The statute defining the offense or a statute related thereto\nexpressly provides that such factual mistake constitutes a defense or\nexemption; or\n (c) Such factual mistake is of a kind that supports a defense of\njustification as defined in article thirty-five of this chapter.\n 2. A person is not relieved of criminal liability for conduct because\nhe engages in such conduct under a mistaken belief that it does not, as\na matter of law, constitute an offense, unless such mistaken belief is\nfounded upon an official statement of the law contained in (a) a statute\nor other enactment, or (b) an administrative order or grant of\npermission, or (c) a judicial decision of a state or federal court, or\n(d) an interpretation of the statute or law relating to the offense,\nofficially made or issued by a public servant, agency or body legally\ncharged or empowered with the responsibility or privilege of\nadministering, enforcing or interpreting such statute or law.\n 3. Notwithstanding the use of the term "knowingly" in any provision of\nthis chapter defining an offense in which the age of a child is an\nelement thereof, knowledge by the defendant of the age of such child is\nnot an element of any such offense and it is not, unless expressly so\nprovided, a defense to a prosecution therefor that the defendant did not\nknow the age of the child or believed such age to be the same as or\ngreater than that specified in the statute.\n 4. Notwithstanding the use of the term "knowingly" in any provision of\nthis chapter defining an offense in which the aggregate weight of a\ncontrolled substance or marihuana is an element, knowledge by the\ndefendant of the aggregate weight of such controlled substance or\nmarihuana is not an element of any such offense and it is not, unless\nexpressly so provided, a defense to a prosecution therefor that the\ndefendant did not know the aggregate weight of the controlled substance\nor marihuana.\n