Mo. Const. art. III, § 19

(a) Senators and representatives shall, in all cases except treason, felony, offenses under this Article, or breach of the peace, be privileged from arrest during the session of the general assembly, and for the fifteen days next before the commencement and after the termination of each session; and they shall not be questioned for any speech or debate in either house in any other place.

(b) Legislative records shall be public records and subject to generally applicable state laws governing public access to public records, including the Sunshine Law. Legislative records include, but are not limited to, all records, in whatever form or format, of the official acts of the general assembly, of the official acts of legislative committees, of the official acts of members of the general assembly, of individual legislators, their employees and staff, of the conduct of legislative business and all records that are created, stored or distributed through legislative branch facilities, equipment or mechanisms, including electronic. Each member of the general assembly is the custodian of legislative records under the custody and control of the member, their employees and staff. The chief clerk of the house or the secretary of the senate are the custodians for all other legislative records relating to the house and the senate, respectively.

(c) Legislative proceedings, including committee proceedings, shall be public meetings subject to generally applicable law governing public access to public meetings, including the Sunshine Law. Open public meetings of legislative proceedings shall be subject to recording by citizens, so long as the proceedings are not materially disrupted.