Mo. Rev. Stat. § 472.060
No judge of probate shall sit in a case in which the judge is interested, or in which the judge is biased or prejudiced against any interested party, or in which the judge has been counsel or a material witness, or when the judge is related to either party, or in the determination of any cause or proceeding in the administration and settlement of any estate of which the judge has been personal representative, conservator, or guardian, when any party in interest objects in writing, verified by affidavit; and when the objections are made, the cause shall be transferred to another judge, in accordance with the provisions of section 478.255, who shall hear and determine same; and the clerk of the circuit court or division clerk shall deliver to the probate division of the circuit court a full and complete transcript of the judgment, order or decree made in the cause, which shall be kept with the papers in the office pertaining to such cause.
§ 472.060, RSMo