Mo. Rev. Stat. § 545.320
No subpoena for a witness in any criminal case shall be issued on the part of the state, unless the name of such witness be endorsed on the indictment or information, or the prosecuting attorney shall order the same to be issued, in writing, or the prosecutor shall file an affidavit that other witnesses ordered by him are positively necessary for a complete adjudication of the case; and no subpoena shall issue for any witness unless the defendant is in custody or on bail, or the clerk or associate circuit judge shall have good reason to believe that he will be apprehended. Subpoenas may be issued to different counties at the same time, but all the witnesses ordered at one time, and living in the same county, shall be included in one subpoena.
§ 545.320, RSMo