S.D. Codified Laws § 2-1-18
Nothing in §§ 2-1-15 to 2-1-18, inclusive, prohibits any interested person who has researched the signatures contained on a validated petition from challenging in circuit court the validity of any signature, the veracity of the petition circulator's attestation, or any other information required on a petition by statute or administrative rule, including any deficiency that is prohibited from challenge under § 2-1-17.1. The results of the process of signature verification by the Office of the Secretary of State under chapter 2-1 shall be presumed valid as applied to all signatures for purposes of considering any additional ground for disqualifying petition signatures, including any ground listed in subdivisions 2-1-17.1(1) to 2-1-17.1(4), inclusive, and cumulating total valid signatures to determine the results of an appeal under § 2-1-17.1. The summons and complaint for a challenge under this section shall be served on each petition sponsor as a party defending the validated petition being challenged. Any appearance by the attorney general at a challenge under this section shall be limited to the process of signature verification by the Office of the Secretary of State under chapter 2-1. For purposes of determining whether a sufficient number of valid signatures has been submitted, the interested person may elect to proceed with a challenge limited to the sample generated in accordance with § 2-1-16, with the resulting valid sample percentage applied to the entirety of the petition signatures.
SDCL 2-1-18