Mo. Rev. Stat. § 287.215

No statement in writing made or given by an injured employee, whether taken and transcribed by a stenographer, signed or unsigned by the injured employee, or any statement which is mechanically or electronically recorded, or taken in writing by another person, or otherwise preserved, shall be admissible in evidence, used or referred to in any manner at any hearing or action to recover benefits under this law unless a copy thereof is given or furnished the employee, or his dependents in case of death, or their attorney, within thirty days after written request for it by the injured employee, his dependents in case of death, or by their attorney. The request shall be directed to the employer or its insurer by certified mail. The term "statement" as used in this section shall not include a videotape, motion picture, or visual reproduction of an image of an employee.