Mo. Rev. Stat. § 106.170: Impeachment trial proceedings.

The members being sworn, the supreme court or the special commission, as the case may be, shall proceed to hear, try and determine such impeachment, and may adjourn the trial to any other time; and the court or commission shall determine all questions of law arising during the trial upon the admissibility of evidence, the competency of witnesses, or otherwise, and may punish any person for contempt committed toward it, or for obstructing the administration of justice on such trial, in as full a manner as any court of record could do for like contempt toward such court. Except as otherwise provided in sections 106.020 to 106.210, the rules of evidence and procedure applicable in civil actions before circuit judges in the circuit courts of this state shall be followed in all trials of impeachment whether before the supreme court or the special commission.