2013 ORS § 163.325¹
Ignorance or mistake as a defense

(1) In any prosecution under ORS 163.355 (Rape in the third degree) to 163.445 (Sexual misconduct) in which the criminality of conduct depends on a childs being under the age of 16, it is no defense that the defendant did not know the childs age or that the defendant reasonably believed the child to be older than the age of 16.

(2) When criminality depends on the childs being under a specified age other than 16, it is an affirmative defense for the defendant to prove that the defendant reasonably believed the child to be above the specified age at the time of the alleged offense.

(3) In any prosecution under ORS 163.355 (Rape in the third degree) to 163.445 (Sexual misconduct) in which the victims lack of consent is based solely upon the incapacity of the victim to consent because the victim is mentally defective, mentally incapacitated or physically helpless, it is an affirmative defense for the defendant to prove that at the time of the alleged offense the defendant did not know of the facts or conditions responsible for the victims incapacity to consent. [1971 c.743 §106]