Mo. Rev. Stat. § 106.040
When the house of representatives shall be satisfied that there is good cause to impeach any officer, they shall cause articles of impeachment to be made out in due form against such officer and shall transmit the same to the supreme court, and immediately elect managers to prosecute such impeachment; provided, however, that in the case of impeachment of the governor or a member of the supreme court, they shall transmit such articles of impeachment to the senate who shall, without delay, proceed to the election of a special commission to try such impeachment as provided in section 106.080. In case of death, resignation or failure to serve, of any manager elected by the house as aforesaid, the governor shall, if the house be not in session, fill such vacancy; and the person thus appointed shall have the same power and perform the same duties as if elected by the house.
§ 106.040, RSMo
RSMo 1939 § 12836, A.L. 1945 p. 1319 § 12838