Mo. Rev. Stat. § 21.220: Expenses paid out of what fund.

All costs and expenses of proceedings, including the necessary expenses of any officer in executing any writ or process of either house or of a joint meeting, and all witness fees, shall be paid:

(1) By the party charged, if so adjudged, and payment may be enforced by execution; or

(2) Out of the contingent fund of the house in which the proceedings are held; or

(3) In case of a joint meeting out of the contingent funds of both houses as the houses by concurrent resolution provide.