Mo. Rev. Stat. § 340.270: Records of patients, discoverable.

In any investigation, hearing or other proceeding to determine a licensee's or applicant's fitness to practice, or in any investigation of a complaint before the board, any record relating to any patient of the licensee or applicant is discoverable by the board and admissible as evidence notwithstanding any privilege to the contrary which such licensee, applicant, or record custodian might otherwise invoke.