45-2-103. General requirements of criminal act and mental state. (1) Except for deliberate homicide as defined in 45-5-102(1)(b) or an offense that involves absolute liability, a person is not guilty of an offense unless, with respect to each element described by the statute defining the offense, a person acts while having one of the mental states of knowingly, negligently, or purposely.
(2) In deliberate homicide under 45-5-102(1)(b), the offender must act while having the mental state of purposely or knowingly only as to the underlying felony referred to in 45-5-102(1)(b).
(3) The existence of a mental state may be inferred from the acts of the accused and the facts and circumstances connected with the offense.
(4) If the statute defining an offense prescribes a particular mental state with respect to the offense as a whole without distinguishing among the elements of the offense, the prescribed mental state applies to each element.
(5) Knowledge that certain conduct constitutes an offense or knowledge of the existence, meaning, or application of the statute defining an offense is not an element of the offense unless the statute clearly defines it as an element.
(6) A person's reasonable belief that the person's conduct does not constitute an offense is a defense if:
(a) the offense is defined by an administrative regulation or order that is not known to the person and has not been published or otherwise made reasonably available to the person and if the person could not have acquired the knowledge by the exercise of due diligence pursuant to facts known to the person;
(b) the person acts in reliance upon a statute that later is determined to be invalid;
(c) the person acts in reliance upon an order or opinion of the Montana supreme court or a United States appellate court later overruled or reversed; or
(d) the person acts in reliance upon an official interpretation of the statute, regulation, or order defining the offense made by a public officer or agency legally authorized to interpret the statute.
(7) If a person's reasonable belief is a defense under subsection (6), nevertheless the person may be convicted of an included offense of which the person would be guilty if the law were as the person believed it to be.
(8) A defense based upon this section is an affirmative defense.