Oregon Revised Statutes Crimes and Punishments § 163.325

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

(2) When criminality depends on the child's 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 to 163.445 in which the victim's 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 victim's incapacity to consent.