Subject to § 29–104 of this subtitle, an application for disability retirement may be submitted: by a member; by a former member; by a surviving beneficiary of a deceased member; or for a member, as provided in subsections (b) through (d) of this section. This subsection does not apply to members of: the State Police Retirement System; the Teachers’ Pension System; or the Teachers’ Retirement System. If a member is unable to apply, the member’s department head may complete and submit an application to the Board of Trustees for the member. This subsection applies to a member of the State Police Retirement System. The Secretary of State Police may complete an application and submit it to the Board of Trustees for a member if: the member is unable or refuses to submit an application for disability retirement; the Secretary believes the member to be permanently physically or mentally incapable of performing assigned duties; there is sufficient medical evidence in the form of a professional opinion of an independent medical practitioner who has recognized expertise in the diagnosis and treatment of the specified illness of the officer to support the Secretary’s determination of permanent disability; the onset of the disability occurred at least 1 year earlier; and any administrative leave granted under § 2-410 of the Public Safety Article has expired. This subsection does not prevent an officer from exercising rights granted under § 21-111(b) of this article. This subsection applies to members of: the Teachers’ Pension System; and the Teachers’ Retirement System. If a member is unable to apply, the member’s State or county superintendent may complete and submit an application to the Board of Trustees for the member.