S.D. Codified Laws § 27A-8-10.1
If a written notice of termination of inpatient treatment is given to the facility pursuant to § 27A-8-10, the notice is not withdrawn, and the facility director or administrator or attending psychiatrist has probable cause to believe that the patient requires emergency intervention under the criteria in § 27A-1-2 and should remain in the facility, the director or administrator or attending psychiatrist may initiate a mental illness hold detaining the patient for a period not to exceed twenty-four hours, not including weekends or holidays, from the facility's receipt of the patient's written notice of intention to terminate. The director or administrator shall immediately advise the patient that he is being detained on a twenty-four hour mental illness hold and explain the nature of such hold. The director or administrator shall forthwith notify the chairman of the county board for the county where the facility is located or a local peace officer of the time of receipt of the notice to terminate, the time the hold was initiated, the circumstances necessitating the hold, and the time and place the director or administrator or attending psychiatrist will be available to file a petition pursuant to § 27A-10-1. This information shall also be made part of the signed petition, the patient's medical records and be delivered to the patient. If a petition pursuant to § 27A-10-1 is not filed with the chair within twenty-four hours of the facility's receipt of the patient's written notice of intention to terminate, the patient shall be immediately discharged. The twenty-four hour period does not include weekends or holidays.
SDCL 27A-8-10.1