Mo. Rev. Stat. § 479.220: Disqualification of judge, when, procedure.

A municipal judge shall be disqualified to hear any case in which he is in any wise interested, or, if before the trial is commenced, the defendant or the prosecutor files an affidavit that the defendant or the municipality, as the case may be, cannot have a fair and impartial trial by reason of the interest or prejudice of the judge. Neither the defendant nor the municipality shall be entitled to file more than one affidavit or disqualification in the same case.