NH CrJI 3.09 MISTAKE OF FACT 
Evidence has been introduced that the defendant acted under a mistaken belief of fact. A person may do the acts which are a crime, but do so with the belief that he has a right to. If you find that this defendant mistakenly acted with the good faith belief that he had a right to do so, then the defendant did not act purposely/knowingly/recklessly and you should find him not guilty. Even if the defendant did not actually have the right to act, if the defendant in good faith believed he had the right to act, you should find him not guilty. The State must prove a reasonable doubt that the defendant acted purposely/knowingly/recklessly.
R.S.A. 626:3, I(a).