1.  Qualification.  Except as provided in subsection 2, a member qualifies for a disability retirement benefit if the member becomes disabled while in service and before reaching normal retirement age.  

2.  Exception.  A member with fewer than 5 years of continuous creditable service immediately preceding that member's application for a disability retirement benefit is not eligible for that benefit if the disability is the result of a physical or mental condition that existed before the member's latest membership in any 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.