Until the time specified in § 8-3452, upon retirement on account of disability a member shall receive an annual disability retirement allowance, payable monthly in equal instalments, in an amount equal to such per cent of his average compensation as may be determined on the basis of the actuarial evaluation set forth in §§ 8-3427 and 8-3428, multiplied by the total years of his current service plus certified prior service, except that in the case of any member who is a commissioned member of the department of safety or of the enforcement and field services division of the game and fish commission such per cent shall be nine-tenths (9/10) of two per cent (2%); however, no member shall be paid a disability retirement allowance less than one-fourth (¼) of his average compensation.
After the time mentioned in § 8-3452, upon retirement on account of disability, a member shall receive a service retirement allowance if he is then eligible, otherwise, a disability retirement allowance, in an amount depending on his class of membership and computed as follows:
However, any commissioned member of the enforcement and field services division of the game and fish commission shall receive a disability retirement allowance in an amount equal to nine-tenths (9/10) of two and one-eighth per cent (21/8%) of his average compensation multiplied by the total number of years of his creditable service, except that the minimum retirement allowance shall be based on twenty (20) years of creditable service or, if less, on the total service that the member would have had if he had continued in service to age fifty-five (55).
However, any fireman or policeman employed by a political subdivision covered under the Tennessee state retirement system shall receive a disability retirement allowance in an amount equal to nine-tenths (9/10) of two and one-fourth per cent (2¼%) of his average compensation multiplied by the total number of years of his creditable service, except that the minimum retirement allowance shall be based on twenty (20) years of creditable service or, if less, on the total service that the member would have had if he had continued in service to age fifty-five (55).
T.C.A. § 8-3507