1.  Qualification.  Except as provided in subsection 2, a member qualifies for a disability retirement benefit if disabled while in service and, for a member who by election remains covered under this section as written prior to its amendment by Public Law 1991, chapter 887, section 7, before normal retirement age.  

2.  Exception.  A member with fewer than 5 years of continuous creditable service preceding that member's last date in service is not eligible for a disability retirement benefit if the disability is the result of a physical or mental condition that existed before the member's membership in a retirement program of the Maine Public Employees Retirement System, unless the disability is a result of, or has been substantially aggravated by, an injury or accident received in the line of duty but from events or circumstances not usually encountered within the scope of the member's employment.  

3.  Qualification of a disabled veteran.  Subject to the provisions in subsections 1 and 2, if a member applying for a disability retirement benefit is receiving disability compensation from the United States Department of Veterans Affairs for a service-connected disability based on a determination of individual unemployability pursuant to 38 Code of Federal Regulations, Section 4.16, it is presumed that the member is disabled under section 17921, subsection 1. This presumption may be rebutted only by evidence not considered by the United States Department of Veterans Affairs in making the individual unemployability determination. Notwithstanding section 17922, this subsection applies to any application for a disability retirement benefit made by a member on or after October 1, 2018.