Mo. Rev. Stat. § 545.050

No indictment for any trespass against the person or property of another, not amounting to a felony, except for petit larceny, and no indictment for the disturbance of the peace of a person, or for libel or slander, shall be preferred unless the name of a prosecutor is affixed thereto, thus: "A B, prosecutor", except where the same is preferred upon the information and testimony of one or more grand jurors, or of some public officer in the necessary discharge of his or her duty.