Mo. Rev. Stat. § 21.170: Expense of serving process — witnesses' fees.

The sergeant at arms or other officer of each house of the general assembly is entitled to receive his actual expenses incurred in the service of all writs and process. Each witness attending either house, or a committee thereof, or a joint meeting of both houses, being summoned, shall have the same fees and traveling allowance as are allowed by law to witnesses for their attendance before circuit courts of this state, to be paid as other costs.