S.D. Codified Laws § 3-12C-518
A current contributing Class B member other than a justice, judge, or magistrate judge, may convert credited service as a county sheriff or deputy county sheriff before January 1, 1980, or credited service as a county sheriff or deputy county sheriff while not certified from January 1, 1980, to June 30, 1988, inclusive; credited service as a police officer while not certified from July 1, 1983, to June 30, 1988, inclusive; credited service as a correctional security staff member before July 1, 1978; credited service as a conservation officer before July 1, 1983; credited service as a parole agent before July 1, 1991; and credited service as an air rescue firefighter before July 1, 1992, from credited service as a Class A member with benefits provided in accordance with § 3-12C-1106 to credited service as a Class B member other than a justice, judge, or magistrate judge, with benefits provided in accordance with § 3-12C-1107, by election to make, or have made on the member's behalf, contributions based on the higher of the member's current compensation, or the member's final average compensation calculated as if the member retired on the date of election, at an actuarially-determined percentage times each year of service for which the member wishes to receive Class B credit. The provisions of this section also apply to a current contributing Class B member, other than a justice, judge, or magistrate judge, who previously has purchased equivalent public service pursuant to the provisions of § 3-12C-509.
Payment of a deposit with the system for the conversion of credited service in accordance with this section shall be determined and due at the time the notice of intention to make the payment is received by the system. The amount due may be paid by periodic level installments over a period of up to ten years, the value of which, if discounted for interest at the assumed rate of return, is equal to the amount due at the date of the notice. If a member dies before completion of the installment payments, the surviving spouse may complete the payments due to the system, but unless the payments are being made by a participating unit, the amount shall be paid in full within ninety days of the member's death or retirement. If the periodic payments are not completed or paid when due, the executive director may make a pro rata adjustment to the credited service, benefits payable under this chapter or schedule of payments to allow for the default.
If the credited service of any member or group of members becomes Class B credited service on a prospective basis after June 30, 1993, the prior credited service as a Class A member may be converted to Class B credited service in accordance with this section. If a jailer becomes a Class B member other than a justice, judge, or magistrate judge, the jailer is eligible to convert prior credited service as a jailer under this section.
SDCL 3-12C-518