Mo. Rev. Stat. § 492.430: Petition for commission to take depositions.

A commission shall be granted to take such depositions by any judge of the supreme court, the court of appeals, or of any circuit court, except a municipal judge, on the presentation of a petition, in writing, of one or more parties, supported by his or their affidavit, or the affidavit of some credible person, setting forth the nature of his or their interest, right or claim, the facts intended to be proved, the names of the individuals whose testimony is desired, and the place or places of their residence.