(a) Any person now serving or having formerly served as a district attorney of a judicial circuit of Alabama, who has served for not less than 18 years, when he has reached the age of 60 years, may elect to become a supernumerary district attorney by filing a written declaration to that effect with the Governor, and time served as judge of a court of record, a county court, county solicitor or any other countywide elected official, a full-time deputy or assistant district attorney or as a duly licensed attorney employed full time by the State of Alabama, whether commissioned or appointed or as an elected constitutional officer or other state official, shall be counted as time served towards accumulating the above required 18 years; provided, that such district attorney shall have served not less than 10 years as district attorney of a judicial circuit.

(b) Any district attorney of a judicial circuit who has served 18 years as circuit district attorney may elect to become a supernumerary district attorney by filing a written declaration to that effect with the Governor, and only two and one-half years served as judge of a court of record, a county court, county solicitor, a full-time deputy or assistant district attorney or as a duly licensed attorney employed full time by the State of Alabama, whether commissioned or appointed or as an elected constitutional officer or other state official, may be counted as time served towards accumulating the above required 18 years.

(c) This section shall not apply to any person who has previously become a supernumerary district attorney prior to October 10, 1975.