S.D. Codified Laws § 7-16-7
The board of county commissioners may by resolution recorded in their minutes, authorize the state's attorney to employ one or more special agents, either continuously or temporarily, to serve upon authorization of the attorney general or his designee, whose duty it shall be to assist the state's attorney in the investigation of crimes. The state's attorney shall inform the attorney general or his designee when special agents are employed or terminated. A special agent shall be a certified law enforcement officer and shall be under the control and direction of the state's attorney. The board of county commissioners, by resolution, shall set a per diem or hourly salary for special agents for actual time worked which shall be paid by the county upon presentation of itemized vouchers approved by the state's attorney. The state's attorney shall maintain offense, investigative and cancellation reports on matters in which he employs special agents in a form substantially similar to those forms used by the division of criminal investigation.
SDCL 7-16-7