Mo. Const. art. I, § 18(b)

Upon a hearing and finding by the circuit court in any case wherein the accused is charged with a felony, that it is necessary to take the deposition of any witness within the state, other than defendant and spouse, in order to preserve the testimony, and on condition that the court make such orders as will fully protect the rights of personal confrontation and cross-examination of the witness by defendant, the state may take the deposition of such witness and either party may use the same at the trial, as in civil cases, provided there has been substantial compliance with such orders. The reasonable personal and traveling expenses of defendant and his counsel shall be paid by the state or county as provided by law. [Effective - 27 Feb 1945 , see footnote]