(1) A person commits the offense of incest if he or she knowingly:
(a) Intermarries or engages in sexual penetration or sexual contact with any person who falls within the degrees of consanguinity set forth in section 28-702;
(b) Engages in sexual penetration or sexual contact with his or her stepchild who is under nineteen years of age; or
(c) Engages in sexual penetration or sexual contact with his or her adopted child or foster child.
(2) Incest is a Class III felony, except that incest with a person who is under eighteen years of age is a Class IIA felony.
(3) For purposes of this section, the definitions found in section 28-318 shall be used.
(4) The testimony of a victim shall be entitled to the same weight as the testimony of victims of other crimes under this code.