(b) On and after a county elects to make the benefits provided herein available, every detective investigator, criminal investigator, senior criminal investigator, confidential criminal investigator, assistant criminal investigator and criminal investigator/arson in the office of a district attorney, entering or re-entering service as such and within one year from the date of entry or re-entry, may elect to contribute to the retirement system pursuant to this section. One year or more after the filing thereof, a member may withdraw any such election by written notice duly acknowledged and filed with the comptroller.

(c) Elections shall be in writing and shall be duly executed and filed with the comptroller.

(e) A member who elects or is required to contribute in accordance with subdivision (a) of this section shall contribute, in lieu of the proportion of compensation as provided in section twenty-one of this article, a proportion of his compensation similarly determined. Such latter proportion shall be computed to provide, at the time when he shall first become eligible for retirement under this section, an annuity equal to one-eightieth of his final average salary for each year of creditable service and as a member rendered after the county wherein he is engaged elected the provisions of this section and prior to the attainment of the age when he shall first become eligible for retirement. Such member's rate of contribution pursuant to this section shall be appropriately reduced pursuant to section seventy-a of this article for such period of time as the county wherein he is engaged contributes pursuant to such section towards pensions-providing-for-increased-take-home-pay. Such member's contribution, reduced as aforesaid, shall also be appropriately further reduced by any multiple of twenty-five percentum of such contribution, reduced as aforesaid, which the county wherein he is engaged has elected to contribute on his behalf in lieu of such member's contributions pursuant to this subdivision. No such member shall be required to make contributions after completing twenty years of such service, except as is provided in subdivision (m) of this section.

(f) (1) A member then covered by the provisions of this section shall be entitled to retire after the completion of twenty years of total creditable service and shall retire upon attainment of age sixty-two by filing an application therefor with the comptroller.

(2) Upon completion of twenty years of such service and upon retirement, each such member shall receive a pension which, together with an annuity which is the actuarial equivalent of his accumulated contributions, if any, at the time of his retirement, and an additional pension which is the actuarial equivalent of the reserve-for-increased-take-home-pay to which he may then be entitled, if any, shall be sufficient to provide him with a retirement allowance equal to one-half of his final average salary.

(3) Upon attainment of the mandatory retirement age of sixty-two years, and upon retirement without completion of twenty years of such service, each such member shall receive a pension which together with an annuity which is the actuarial equivalent of his accumulated contributions at the time of his retirement and an additional pension which is the actuarial equivalent of the reserve-for-increased-take-home-pay to which he may then be entitled, shall be sufficient to provide him with a retirement allowance equal to one-fortieth of his final average salary for each year of creditable service in a district attorney's office. Every such member shall also be entitled to an additional pension for other service as provided under paragraphs three and four of subdivision a of section seventy-five of this article. This latter pension shall not increase the total allowance to more than one-half of his final average salary.

(4) For the purpose only of determining the amount of the pension provided in subdivisions (f) and (m) of this section, the annuity shall be computed as it would be if it were not reduced by the actuarial equivalent of any outstanding loan, and if it were not increased by the actuarial equivalent of any additional contributions, and if it were not reduced by reason of the member's election to decrease his annuity contributions to the retirement system in order to apply the amount of such reduction in payment of his contributions for old-age and survivors insurance coverage.

(g) The entire additional cost for the increased pensions to members, as provided by this section, shall be paid from additional contributions made by the participating employer on account of such members. The actuary of the retirement system shall compute the additional contribution required for each member who elects to receive the special benefits provided under this section. Such additional contributions shall be computed on the basis of contributions during the prospective service of such member which will cover the liability of the retirement system for such extra pensions. Upon approval of the comptroller, such additional contributions shall be certified by him to the fiscal officer of the participating employer. The amount thereof shall be included in the annual appropriation of the participating employer for its district attorney's office. Such amount shall be paid to the pension accumulation fund of the retirement system.

(h) As used in this section "creditable service" shall include all criminal law enforcement services performed as a detective investigator, criminal investigator, senior criminal investigator, confidential criminal investigator, assistant criminal investigator or criminal investigator/arson in the office of a district attorney, provided, however, that criminal law enforcement service shall only be creditable when it aggregates fifty percentum or more of such service.

(i) Credit for service as a member or officer of the state police, or as a paid firefighter, police officer or officer of any organized fire department or police force or department of any county, city, village, town, fire district or police district or as a sheriff, undersheriff or regular deputy sheriff or as a criminal investigator in the office of a district attorney, shall also be deemed to be creditable service and shall be included in computing years of total service for retirement pursuant to this section, provided such service was performed by the member while contributing to the retirement system pursuant to this article or article eight of this chapter.

(j) The county wherein the member is engaged may, in its initial action taken under this section or subsequent thereto, elect to assume and pay all or part of the additional cost on account of service rendered to the county prior to the effective date of such election and, in addition, may in its initial action taken under this section or subsequent thereto, elect to assume and pay all or any multiple of twenty-five per centum of the additional cost on account of service rendered on and after the effective date of such election. The county shall pay the additional cost so assumed by any such election by means of annual contributions which shall be determined by the actuary.

(k) A member contributing on the basis of this section at the time of retirement, shall be retired on December thirty-first of the year in which he attains sixty-two years of age. Application therefor may be filed in a manner similar to that provided in section seventy of this article.

(l) The benefits of this section shall be available only to those members whose employer elects to provide such benefits by adopting a resolution to such effect and filing a certified copy thereof with the comptroller.

(m) Upon completion of twenty years of total creditable service and upon retirement, each member covered by the plan provided by this section shall receive, for each year of creditable service in excess of twenty, but not more than ten such years, an additional retirement allowance equal to one-sixtieth of his final average salary for each such year of such service; provided, however, that this benefit shall be available only after the county employing such member elects specifically to provide this benefit. Member contributions, if any, shall be computed in a manner consistent with subdivision (e) of this section so as to provide an annuity of one hundred twentieth of final average salary for each such year of service and employers shall have the further option to reduce contributions in a manner similar to that provided in said subdivision (e).

(n) Notwithstanding the provisions of article eleven of this chapter, a detective investigator, criminal investigator, senior criminal investigator, confidential criminal investigator, assistant criminal investigator and criminal investigator/arson in the office of district attorney that otherwise qualifies for retirement under this section may retire after the completion of twenty years total creditable service without regard to age with a retirement allowance equal to one-half of such persons final average salary.

(o) The provisions of this section shall, subject to the provisions of section seventy-six of this article, apply to members who, on and after June first, nineteen hundred eighty-three retire or separate in vested status from service with a participating employer who has elected to provide the benefits hereunder.