Mo. Rev. Stat. § 512.310
The trial de novo shall be governed by the practice in trials before circuit judges, except that by agreement of parties the case may be tried by a jury of not less than six persons.
(RSMo 1939 § 2747, A.L. 1945 p. 765 § 142, A.L. 1978 H.B. 1634, A.L. 1985 S.B. 5, et al. § B, A.L. 1986 S.B. 741)
Effective 1-01-87