Miss. Code § 99-39-7
The motion under this article shall be filed as an original civil action in the trial court, except in cases in which the petitioner's conviction and sentence have been appealed to the Supreme Court of Mississippi and there affirmed or the appeal dismissed. Where the conviction and sentence have been affirmed on appeal or the appeal has been dismissed, the motion under this article shall not be filed in the trial court until the motion shall have first been presented to a quorum of the Justices of the Supreme Court of Mississippi, convened for said purpose either in termtime or in vacation, and an order granted allowing the filing of such motion in the trial court. The procedure governing applications to the Supreme Court for leave to file a motion under this article shall be as provided in Section 99-39-27.
Miss. Code § 99-39-7