S.D. Codified Laws § 55-3-11
Current with legislation signed by the governor on or before 3/6/2024
A trustee must invest money received by him under the trust, as fast as he collects a sufficient amount, in such manner as to afford reasonable security and interest for the same.
If he fails so to do, he must pay simple interest thereon if such omission is merely negligent, and compound interest thereon if it is willful.
SDCL 55-3-11