Mo. Rev. Stat. § 217.805
For any fine imposed by any statute, and for any forfeiture of a recognizance, where the securities are made liable, the governor shall have power to grant a remittitur, when it shall be made to appear to him that there is by such fine or forfeiture an injustice done, or great hardship suffered by the defendant or defendants, which equity and good conscience would seem to entitle relief for the defendant or defendants. All applications for such relief shall be in writing, signed by the party or parties seeking such remittitur, and accompanied by a statement of the facts of the case, signed by the judge or prosecuting attorney of the county in which such fine or forfeiture is entered, and a certificate of the clerk that all costs have been paid; and the governor shall endorse his decision on each case and file the same in the office of the secretary of state.
§ 217.805, RSMo