Mo. Rev. Stat. § 106.080

If the governor or a judge of the supreme court shall be impeached, the house of representatives shall immediately transmit such articles of impeachment to the senate who shall, without delay, proceed to the election of a special commission to try the cause, which commission shall be composed of seven eminent jurists, who at the time of their election are judges of the circuit or appellate courts of this state; provided, however, that judges of the supreme court shall not be eligible to serve on such special commission. The commission shall meet in the City of Jefferson within thirty days after their election on a day designated by the senate.