Mo. Rev. Stat. § 491.180: Penalty where party refuses to attend and testify.

If a party, on being duly summoned, refuse to attend and testify, either in court or before any person authorized to take his deposition, besides being punished himself as for a contempt, his petition, answer or reply may be rejected, or a motion, if made by himself, overruled, or, if made by the adverse party, sustained.