S.D. Codified Laws § 21-42-21
In counties where it shall be determined by the board of county commissioners of such county that the state's attorney of such county is unable to handle the work required in the prosecution of the action or actions as herein authorized by reason of the additional work imposed upon him by the adoption of this chapter, then and in such cases, the state's attorney is hereby authorized to contract with additional counsel to prosecute and bring such action or actions herein authorized, which additional counsel shall be by the state's attorney appointed as an assistant state's attorney, the contract with such additional counsel to be approved by the county commissioners, and his compensation paid out of the appropriate fund of said county.
SDCL 21-42-21