§ 559. Application. For purposes of accidental disability retirement only, a sheriff, undersheriff or deputy sheriff engaged directly in criminal law enforcement activities that aggregate fifty per centum of his or her service and are police officers under the criminal procedure law who last joined a public retirement system of the state or a municipality thereof, on or after July first, nineteen hundred seventy-three, but prior to January first, nineteen hundred eighty-five, shall be subject to the provisions of article eleven of this chapter that apply to members of the state and local police and fire retirement system.