Sec. 6. DISABILITY PENSION BENEFITS. (a) If the board determines that a member has suffered an on-duty disability, the member is entitled to an on-duty disability pension as provided by this section in lieu of any other benefit under this article.

(b) If the board determines that a member is not capable of performing the usual and customary duties of the member's classification or position because of the member's on-duty disability, the member is entitled to receive a monthly disability pension, beginning after the effective date of the member's termination of active service, in an amount equal to the greater of:

(1) 50 percent of the member's average monthly salary; or

(2) the service pension the member would have been entitled to receive under Section 4 of this article based on years of participation as of the effective date of the member's termination of active service.

(c) If the board determines that a member is not capable of performing any substantial gainful activity because of the member's on-duty disability, the member is entitled to receive a monthly disability pension, beginning after the effective date of the member's termination of active service, in an amount equal to the greater of:

(1) 75 percent of the member's average monthly salary; or

(2) the service pension the member would have been entitled to receive under Section 4 of this article based on years of participation on the effective date of the member's termination of active service.

(d) If a full-time active member with at least six years of service becomes disabled or dies from heart or lung disease or cancer, and the member successfully passed a physical examination before the claimed disability or death or on beginning employment as a firefighter, and the examination failed to reveal any evidence of the heart or lung disease or cancer, that condition will be presumed to have caused an on-duty disability for purposes of determining eligibility for disability benefits under this section, and the amount of the disability benefit is presumed to constitute, unless the presumption is rebutted, the pension amount that shall be used to determine the death benefit payable with respect to that member. The on-duty disability presumption may be rebutted only by clear and convincing evidence. Another statutory presumption regarding the cause of illnesses or conditions does not affect any benefit payable under this article.

(e) If the board determines that a member is not capable of performing the usual and customary duties of the member's classification or position because of the member's off-duty disability, the member is entitled to an off-duty disability pension in lieu of any other benefit under this article. If the board makes that determination, the member is entitled to receive a monthly disability pension, beginning after the effective date of the member's termination of active service, in an amount equal to the greater of:

(1) 25 percent of the member's average monthly salary, plus 2-1/2 percent of the member's average monthly salary for each full year of participation in the fund, except that the total monthly disability pension under this subdivision may not exceed 50 percent of the member's average monthly salary; or

(2) the service pension the member would have been entitled to receive under Section 4 of this article based on years of participation on the effective date of the member's termination of active service.

(f) A member is not eligible for an on-duty or off-duty disability pension as provided by this section if the member's on-duty or off-duty disability is a direct and proximate result of a condition that existed on the date the member began membership in the fund. In that event, if the member is not eligible to receive a service pension under Section 4 of this article, the member may elect any deferred pension or refund of contributions for which the member is eligible under Section 8 of this article. A member has a preexisting condition under this subsection if the board determines that the member had:

(1) symptoms that would cause an ordinarily prudent person to seek diagnosis, care, or treatment during the five-year period before the effective date of the member's membership in the fund; or

(2) a condition for which medical advice or treatment was recommended by or received from a physician during the five-year period before the effective date of the member's membership in the fund.

(g) The board shall review, on a case-by-case basis, existing benefit payments to members, and to survivors of deceased members, who retired as a result of a disability with 20 or more years of service under a provision of any predecessor statute previously governing the fund. The review will determine whether the member's disability was an on-duty disability that satisfies the requirements of Subsection (b) or (c) of this section. A determination that a member's disability was an on-duty disability, as described above, will apply only on a prospective basis beginning with January 1 of the calendar year in which the determination is made and will not affect the amount of the member's or survivor's benefits. The board shall make its review and determination under this subsection on the basis of the medical evidence and any other relevant non-testimonial evidence that was previously submitted in connection with the prior application for benefits, except that if the board finds that the historical file is insufficient to make the determination, supplemental evidence of a probative nature may be adduced and accepted to help make the determination.

(h) A person may not receive an on-duty or off-duty disability pension from the fund unless the person or the person's legal representative files with the board an application for disability benefits, in the form approved by the board, and certificates of the member's disability signed and sworn to by the member and the member's physician or by a physician selected by the board. The board may require other or additional evidence of disability before authorizing payment of disability pension benefits.

(i) The board shall make all determinations concerning benefits under this section in accordance with uniform principles consistently applied on the basis of medical or other evidence that the board determines is necessary or desirable.