South Dakota Codified Laws
Chapter 22A - Offenses Against The Family
Section 22-22A-2 - Incest--Prohibited sexual contact--Felony.

22-22A-2. Incest--Prohibited sexual contact--Felony.
Any persons, eighteen years of age or older, who knowingly engage in a mutually consensual act of sexual penetration with each other:
(1)Who are not legally married; and
(2)Who are within degrees of consanguinity within which marriages are, by the laws of this state, declared void pursuant to §25-1-6;
are guilty of incest. Incest is a Class 5 felony.

Source: SL 2005, ch 120, §20.