Mo. Rev. Stat. § 104.602

104.602. Creditable service not previously credited to members of either system to be credited, when — duplicate credit prohibited — death of a member prior to exercise of transfer rights, rights of survivor. — 1. Any member as defined in section 104.010 may elect prior to retirement to receive creditable service with the system of which he or she is a current member equal to all creditable service or any forfeited service performed for a department covered by the other system. In no event shall a member under either system established pursuant to this chapter receive credit in more than one system for the same period of service.

2. If a member dies before retirement and prior to exercising transfer rights pursuant to the provisions of this section, the survivor may elect to receive survivor benefits that shall be computed as if the member had in fact exercised the member's transfer rights to produce the most advantageous benefit possible. In this instance, the benefit shall be paid by the system that provides the most advantageous benefit. If there is no advantage in one system or the other after the transfer of creditable service, the benefit shall be paid by the system that the member last accrued service under prior to the date of the death of the member.

(L. 1981 H.B. 835, et al., A.L. 1982 H.B. 1720, et al., A.L. 1984 H.B. 1370, A.L. 1988 H.B. 1643 & 1399, A.L. 1997 H.B. 356, A.L. 2001 S.B. 371)