Mo. Rev. Stat. § 103.141
The persons in each participating member agency eligible for coverage by the plan shall include, subject to the limitations contained in sections 103.003 to 103.175:
(3) All persons who become eligible for retirement benefits because of service with the participating member agency, persons who become eligible for a disability benefit from the participating member agency, and their unemancipated dependents, on or after the date such participating member agency becomes covered under the plan, and who have been continuously covered by the benefits under sections 103.003 to 103.175 for at least the shorter of:
(L. 1992 H.B. 1574 § 4 subsec. 5)