S.D. Codified Laws § 23A-27A-26.3
Not later than ninety days before the commencement of trial, the defendant may upon a motion alleging reasonable cause to believe the defendant was intellectually disabled at the time of the commission of the offense, apply for an order directing that an intellectual disability hearing be conducted before trial. If, upon review of the defendant's motion and any response to the defendant's motion, the court finds reasonable cause to believe the defendant was intellectually disabled, the court shall promptly conduct a hearing without a jury to determine whether the defendant was intellectually disabled. If the court finds after the hearing that the defendant was not intellectually disabled at the time of the commission of the offense, the court shall, before commencement of trial, enter an order stating the court's finding. Nothing in this paragraph precludes the defendant from presenting mitigating evidence of an intellectual disability at the sentencing phase of the trial. If the court finds after the hearing that the defendant established an intellectual disability by a preponderance of the evidence, the court shall before commencement of trial, enter an order stating the court's finding. Unless the order is reversed on appeal, a separate sentencing proceeding under this section may not be conducted if the defendant is thereafter convicted of murder in the first degree. If a separate sentencing proceeding is not conducted, the court, upon conviction of a defendant for the crime of murder in the first degree, shall sentence the defendant to life imprisonment.
SDCL 23A-27A-26.3