Haw. Rev. Stat. § 702-218: Ignorance or mistake as a defense.

In any prosecution for an offense, it is a defense that the accused engaged in the prohibited conduct under ignorance or mistake of fact if:

(1) The ignorance or mistake negatives the state of mind required to establish an element of the offense; or

(2) The law defining the offense or a law related thereto provides that the state of mind established by such ignorance or mistake constitutes a defense. [L 1972, c 9, pt of §1]

COMMENTARY ON §702-218

[Section 218, as contained in the Proposed Draft of the Code provided that ignorance or mistake of fact or law was a defense under the conditions stated above. The following commentary is based on this initial proposal for §218.]

This section states the logical concomitant of the requirement that to establish each element of an offense a certain state of mind with respect thereto must be proven. Thus, if a person is ignorant or mistaken as to a matter of fact or law, the person's ignorance or mistake will, in appropriate circumstances, prevent the person from having the requisite culpability with respect to the fact or law as it actually exists. For example, a person who is mistaken (either reasonably, negligently, or recklessly) as to which one of a number of similar umbrellas on a rack is the person's and who takes another's umbrella should be afforded a defense to a charge of theft predicated on either intentionally or knowingly taking the property of another. Also, a person, mistaken as to the effect of a divorce decree erroneously purporting to sever the marital ties of his wife, who marries another woman should not be convicted of bigamy if bigamy requires knowledge by the defendant of the defendant's existing marital status. A reckless mistake would afford a defense to a charge requiring intent or knowledge--but not to an offense which required only recklessness or negligence. Similarly, a negligent mistake would afford a defense to a charge predicated on intent, knowledge, or recklessness--but not to an offense based on negligence.

This section of the Code deals with ignorance or mistake of fact or law, but it is not intended to deal with the limited problem of the defense afforded a person who engaged in conduct under the mistaken belief that the conduct itself was not legally prohibited. That problem is dealt with exclusively by §702-220.