NYSentencing

§ 15.20  Effect of ignorance or mistake upon liability.
  1.  A person is not relieved of criminal liability for conduct because
he engages in such conduct under a mistaken belief of fact, unless:
  (a)  Such factual mistake negatives the culpable mental state required
for the commission of an offense; or
  (b)   The  statute  defining  the offense or a statute related thereto
expressly provides that such factual mistake constitutes  a  defense  or
exemption; or
  (c)   Such  factual  mistake  is  of a kind that supports a defense of
justification as defined in article thirty-five of this chapter.
  2.  A person is not relieved of criminal liability for conduct because
he engages in such conduct under a mistaken belief that it does not,  as
a  matter  of law, constitute an offense, unless such mistaken belief is
founded upon an official statement of the law contained in (a) a statute
or  other  enactment,  or  (b)  an  administrative  order  or  grant  of
permission, or (c) a judicial decision of a state or federal  court,  or
(d)  an  interpretation  of  the statute or law relating to the offense,
officially made or issued by a public servant, agency  or  body  legally
charged   or   empowered   with   the  responsibility  or  privilege  of
administering, enforcing or interpreting such statute or law.
  3.   Notwithstanding  the use of the term "knowingly" in any provision
of this chapter defining an offense in which the age of a  child  is  an
element  thereof, knowledge by the defendant of the age of such child is
not an element of any such offense and it is not,  unless  expressly  so
provided, a defense to a prosecution therefor that the defendant did not
know the age of the child or believed such age to  be  the  same  as  or
greater than that specified in the statute.
  4. Notwithstanding the use of the term "knowingly" in any provision of
this chapter defining an offense in which  the  aggregate  weight  of  a
controlled  substance  or  marihuana  is  an  element,  knowledge by the
defendant of the  aggregate  weight  of  such  controlled  substance  or
marihuana  is  not  an element of any such offense and it is not, unless
expressly so provided, a defense to  a  prosecution  therefor  that  the
defendant  did not know the aggregate weight of the controlled substance
or marihuana.