Mo. Rev. Stat. § 84.440
In case any police official shall have reason to believe that any person has committed, or is about to commit, within the city or on public property of said city beyond the corporate limits thereof any breach of peace or violation of law and order, or that any person found within the city or on public property of said city beyond the corporate limits thereof is charged with the commission of crime in the state of Missouri, against whom criminal proceedings shall have been issued, or when any person may have committed an offense within view of a member of such police force, said police official may cause such person to be arrested by any member of the police force. In cases where officers make arrest for crime committed within their view, the offenders shall at once be conveyed before some police judge or some judge in the city and the proper complaint against him shall be filed by said officer.
§ 84.440, RSMo