S.D. Codified Laws § 55-1A-41
Unless specifically restricted by the governing instrument, a trustee may appoint an individual or a corporate fiduciary as a co-trustee. The appointed co-trustee may serve only as long as the appointing trustee serves, or as long as the last to serve if more than one trustee appointed the co-trustee. The appointed co-trustee may not become a successor trustee upon the death, resignation, or incapacity of the appointing trustee, unless appointed under the terms of the governing instrument or unless no other successor trustee, or method for appointing a successor trustee, is provided in the governing instrument.
The powers and the responsibilities of the appointed co-trustee may be limited by the appointing trustee in a writing signed by the appointing trustee at the time of the appointment. If the powers or responsibilities are so limited, the powers or responsibilities of the co-trustee shall be limited as set forth in writing. Unless the powers or responsibilities are so limited, the appointed co-trustee may exercise all the powers of the appointing trustee. The combined powers of the appointed co-trustee and the appointing trustee may not exceed the powers of the appointing trustee alone. The trustee appointing a co-trustee may, in writing, revoke the appointment at any time, with or without cause.
Unless specifically restricted by the governing instrument, if the governing instrument gives a fiduciary other than the trustee the power to remove and replace the trustee, such power includes the power to appoint a co-trustee to serve with the current trustee.
If an appointment under this section confers upon the appointed co-trustee, to the exclusion of another co-trustee, the power to take certain actions, including the power to direct or prevent certain actions of the trustees, the limitations on liability and the relief from duties and obligations afforded an excluded fiduciary under § 55-1B-2 apply to a co-trustee who does not hold such power.
If the governing instrument is silent concerning the trustee's power to appoint a co-trustee, the trustee shall notify in writing, the trustor, if living, and all current income and principal beneficiaries at least thirty days prior to the effective date of the trustee's exercise of the power granted under this section. The notice, which shall include a copy of the proposed action, shall advise the trustor and current beneficiaries that if they object to the trustee's appointment they need to file a written objection with the trustee prior to the effective date set out in the notice of the proposed action. If an objection is received by the trustee, prior to the effective date of the appointment, the trustee may not appoint a co-trustee. However, this section does not limit the power of the trustee under law to petition the court for approval of the appointment. If no objection has been timely made, the proposed appointment becomes effective on the later of the date set out in the notice or thirty days after notice has been given. The notice must be sent by any means allowed under the terms of the trust instrument, by mail with postage prepaid to the last known address of the trustor or current beneficiary, or by means otherwise allowed by law.
A governing instrument may provide for the appointment of two or more trustees and confer or allocate on one or more of the trustees, to the exclusion of other trustees, the power to direct, veto, or overrule specified actions or decisions of other trustees, or with sole responsibility for certain trustee duties. Any excluded trustee shall act in accordance with the exercise of the power, is not liable for complying with the exercise of the power, and has no obligation to review, inquire, investigate, or undertake any recommendations or evaluations with respect to the exercise of the power. A trustee having the power has the sole duty to account to the beneficiaries with respect to the exercise of the power and, if found liable for a breach of the trustee's duties with respect to the exercise of the power, is liable as if that trustee were the sole trustee.
The provisions of this section are effective for trusts created before, on, or after July 1, 2017, except as otherwise directed by the trustor, trust protector, trust advisor, or other fiduciary designated by the terms of the trust.
SDCL 55-1A-41