Mo. Rev. Stat. § 58.290

Every person summoned as a juror, who shall fail to appear, or make a reasonable excuse to the coroner for his nonattendance, within five days after the time appointed within the warrant, shall forfeit and pay the sum of five dollars, which fine shall be recoverable by civil action at the instance of the coroner, and in the name of the state, before any associate circuit judge, and be applied to the use of the county.