(a) An assistant prosecutor is entitled to longevity pay if the assistant prosecutor:
(1) is a full-time employee on the last day of a state fiscal quarter;
(2) is not on leave without pay on the last day of a state fiscal quarter; and
(3) has accrued at least four years of lifetime service credit not later than the last day of the month preceding the last month of a state fiscal quarter.
(b) The district attorney, criminal district attorney, or county attorney in the county in which the assistant prosecutor is employed shall certify the eligibility of the assistant prosecutor to receive a longevity pay supplement under this subchapter.