S.D. Codified Laws § 4-11-21
The identity of a person supplying information to the Department of Legislative Audit in conjunction with the performance of any audit authorized by this chapter may be kept confidential if requested by that person and such confidentiality is determined by the auditor general to be appropriate under the circumstances. After a determination of confidentiality has been made, the identity of the person supplying the information may not be disclosed except pursuant to written consent of that person or by court order. No person may use a subpoena, discovery, or other applicable statute to obtain the identity of the person. This section does not apply to requests from the attorney general or law enforcement officers of any municipality, county, state, or federal agency or department for such information.
SDCL 4-11-21