A. A male person commits unlawful sexual intercourse if he has sexual intercourse with a female, not his wife, who is under sixteen years of age when at the time of intercourse the male is no more than three years older than the female.

B. Unlawful sexual intercourse is a class B misdemeanor. Evidence that the actor was not more than three years older than the victim at the time of the intercourse shall be raised by the defendant. (Code 1975 § 13-540)