Mo. Rev. Stat. § 491.140: Witness liable to action, when.

When a party causing a witness to be summoned, shall have paid or tendered to such witness his legal fees for traveling, and one day's attendance, at the time of summoning such witness, if he fail to attend he shall be liable to the action of the party for all damages sustained by the nonattendance, unless he show sufficient cause to justify such absence.