Mo. Rev. Stat. § 106.180

In all such trials the accused shall have a right to be heard by himself and his counsel, and all matters relating to procedure and the conduct of the trial shall be determined by a majority vote of the judges or commissioners and shall be entered and made a part of the record of the proceeding; but no judgment or sentence of conviction shall be given against any person upon any impeachment without concurrence of five-sevenths of the judges of the supreme court or of the members of the special commission.