Mo. Rev. Stat. § 544.290

An associate circuit judge shall be disqualified to conduct an examination of any person accused of felony as provided in this chapter if an affidavit is filed in his office by the accused, the prosecuting attorney, or the complainant, before the commencement of such examination, stating that the associate circuit judge is near of kin to the accused by blood or marriage; or that the offense charged is alleged to have been committed against the person or property of such associate circuit judge; or against some person near of kin to him by blood or marriage; or that the associate circuit judge is in anywise interested or prejudiced, or shall have been counsel in the matter, as the affiant verily believes.