Mo. Rev. Stat. § 86.1170

86.1170. Pension benefit after twenty-five years of service or injury in line of duty, when — retirees appointed as consultants to board, when. — 1. Any member who retires after August 28, 2000, who is entitled to a pension benefit under the provisions of sections 86.900 to 86.1280 and who either has at least twenty-five years of creditable service or is retired as a result of an injury or illness occurring in the line of duty or course of employment under section 86.1180 , shall receive a pension benefit which, without including any supplemental retirement benefits paid such member by the retirement system, shall be six hundred dollars monthly. Any member who retired on or before August 28, 2000, who is entitled to a pension benefit under the provisions of sections 86.900 to 86.1280 and who either had at least twenty-five years of creditable service or was retired as a result of an injury or illness occurring in the line of duty or course of employment under section 86.1180 , shall upon application to the retirement board be appointed by the retirement board as a consultant and shall, beginning the later of August 28, 2000, or the time of such appointment under this subsection or a previously applicable statute, be compensated in an amount which, without including any supplemental retirement benefits provided by this system, shall be not less than six hundred dollars monthly. A pension benefit under this subsection shall be paid in lieu of such member's base pension as increased by cost-of-living adjustments granted under section 86.1220 . The benefit under this subsection shall not be subject to cost-of-living adjustments, but shall be terminated and replaced by the member's base pension and cost-of-living adjustments at such time as the total base pension and such adjustments exceed six hundred dollars monthly.

2. Any member who retired on or before August 28, 2009, who is entitled to a pension benefit under the provisions of sections 86.900 to 86.1280 and was retired under section 86.1200 shall, upon application to the retirement board, be appointed by the retirement board as a consultant and shall, beginning August 28, 2009, or the time of such appointment under this subsection, whichever is later, be compensated in an amount which, without including any supplemental retirement benefits provided by sections 86.900 to 86.1280 , shall be six hundred dollars monthly. A pension benefit under this subsection shall be paid in lieu of such member's base pension as increased by cost-of-living adjustments granted under section 86.1220 . The benefit under this subsection shall not be subject to cost-of-living adjustments, but shall be terminated and replaced by the member's base pension and cost-of-living adjustments at such time as the total base pension and adjustments exceed six hundred dollars monthly.

(L. 2005 H.B. 323, A.L. 2009 H.B. 397 & H.B. 947)