S.D. Codified Laws § 3-12C-1114

Upon the death of any foundation member who has reached normal retirement age or who has retired with a benefit payable from the system, the surviving spouse is eligible to receive a benefit, payable in monthly installments, equal to sixty percent of the retirement benefit that the foundation member was receiving or was eligible to receive at the time of death. The surviving spouse benefit of a spouse of a retiree is effective the first day of the month following the death of the member and is payable upon the receipt of a completed application. The surviving spouse benefit of a spouse of a member who had reached normal retirement age, but had not begun a retirement benefit, is effective the first day of the month following the date on which the member's contributory service terminates and is payable upon the receipt of a completed application.