S.D. Codified Laws § 9-16-5.10
Every fiduciary of a retirement system subject to the provisions of this chapter shall discharge his duties solely in the interest of the participants and beneficiaries of the system, for the exclusive purpose of providing benefits to participants and their beneficiaries and with the skill, care, prudence, and diligence, under the circumstances then prevailing, of a prudent man, familiar with such matters and acting in a similar capacity. For purposes of this section, the term "fiduciary" means any person or entity which exercises any discretionary authority control over the management of a system or its assets, any person or entity which renders investment advice to a system for a fee or other compensation, or any person or entity which has any discretionary authority or discretionary responsibility in the administration of a system.
SDCL 9-16-5.10