S.D. Codified Laws § 27A-7-1
In each county a magistrate judge or lawyer shall be appointed by the presiding circuit judge of the circuit in which the county is situated to serve as the chair of the county board of mental illness. Any board conducting commitment hearings shall consist of the chair and two other persons appointed by the board of county commissioners for a three-year term. The two members appointed by the county commission shall be residents of the county. The chair appointed by the presiding circuit judge need not be a resident of the county. The members of the board of mental illness who are appointed by the board of county commissioners may be appointed to more than one term but may not serve more than two consecutive three-year terms. The state's attorney for the county may not serve on the county board of mental illness. Each appointing authority shall also appoint alternates.
Pursuant to chapter 1-24, two or more counties may jointly contract to establish a board of mental illness to serve all contracting counties. In such case, the county commissioners of the contracting counties shall jointly appoint the two board members referred to in this section. The members may be residents of any of the counties under joint contract.
SDCL 27A-7-1