Mo. Rev. Stat. § 545.040: Indictments signed by whom.

Every indictment must be attributed to the prosecuting attorney, and when the grand jury returns* any indictment into the court the judge must examine it, and if the foreman has neglected to endorse it "a true bill", with his name affixed thereto, or if the prosecuting attorney has not affixed his or her name to the indictment, the court must cause the foreman to affix his or her name or the prosecuting attorney to affix his or her name, as the case may require.