Mo. Rev. Stat. § 115.261: Voting machine not to be unlocked or opened during election, exception.

During an election, no door, compartment, or lock shall be unlocked or opened, except by direction of the election authority, and then only for good and sufficient reason. If the door, compartment, or lock on any machine is opened by the election authority or his representative, the reason for such opening shall be stated in writing, signed by the election authority or his representative and attached to one statement of returns.