Mo. Rev. Stat. § 545.490
The petition of the applicant for a change of venue shall set forth the facts or grounds upon which such change is sought, and such petition shall be supported by the affidavit of petitioner and the affidavit of at least two credible disinterested citizens of the county where said cause is pending and the truth of the allegations thereof shall be proved, to the satisfaction of the court, by legal and competent evidence, and the prosecuting attorney may in such case offer evidence in rebuttal of that submitted in support of such application; the court, or judge in vacation, shall fix the number of witnesses for which the state or county may be liable; provided, in all cases in counties in this state which now have or may hereafter have a population of less than seventy-five thousand inhabitants if such petition for change of venue is supported by the affidavits of five or more credible disinterested citizens residing in different neighborhoods of the county where said cause is pending, then the court or judge in vacation, shall grant such change of venue, as of course, without additional proof; provided further, that reasonable previous notice of such application shall in all cases be given to the prosecuting attorney; and provided further, that if the facts alleged as the ground of the application be within the knowledge of the court or judge, he may order such removal of the cause without any formal proof or the filing of affidavit; and provided further, that if the application shall allege prejudice of the inhabitants of more than one county in the circuit in which the case is pending, the court may, upon proof of the allegations as herein provided for, order the case sent to some county in the same or some other circuit where such causes do not exist.
§ 545.490, RSMo