SDCL § 18-4-18: Proof of instrument by subscribing witness.

If proof of the execution of an instrument is made by a subscribing witness, such witness must be personally known to the officer taking the proof to be the person whose name is subscribed to the instrument as a witness or must be proved to be such by the oath of a credible witness. The subscribing witness must prove that the person whose name is subscribed to the instrument as a party is the person described in it and that such person executed it and that the witness subscribed his name thereto as a witness.