Mo. Rev. Stat. § 508.100

If a judge is interested in the cause before him, or related to either party, or has been of counsel in the cause, the court, without application from either party, shall either call in another circuit judge to sit in the case, as authorized by Section 15 of Article V of the Constitution, or request the supreme court to transfer a judge to try the cause, as authorized by Section 6 of Article V of the Constitution, unless all the parties in the cause consent that such judge may sit in the trial thereof.