Mo. Rev. Stat. § 545.410
When any prosecuting attorney shall be notified of the taking of any deposition, as specified in section 545.400, it shall be his duty to attend the taking thereof if the same shall be taken in his county, but if in any other county in this state, he shall immediately notify the prosecuting attorney of the county where such deposition is to be taken, giving him such information as will enable him to represent the state at the taking of the same; and it is hereby made the duty of such prosecuting attorney, upon receiving such information, to attend the taking thereof in behalf of the state. If any such deposition be taken out of the state, the prosecuting attorney may employ counsel to attend and represent the state at the taking of the same, at a fee not to exceed ten dollars for the first witness examined, and one dollar for each additional witness examined, which fee shall be taxed and paid as other costs in the case.
§ 545.410, RSMo