S.D. Codified Laws § 34-12D-2
A competent adult may at any time execute a declaration governing the withholding or withdrawal of life-sustaining treatment. The declaration must be signed by the declarant, or by another at the declarant's direction, and witnessed by two adults, or by a notary public who shall thereafter notarize the declaration.
A declaration must state the declarant's preferences regarding the provision, withholding, or withdrawal of artificial nutrition and hydration.
If the declaration does not state the declarant's preferences regarding the provision, withholding, or withdrawal of artificial nutrition and hydration, any determination regarding the provision, withholding, or withdrawal of artificial nutrition and hydration is governed by the laws of this state that apply in the absence of a declaration.
SDCL 34-12D-2