Section 455. Cooperation of the police department

a. It shall be the duty
  of the police department to provide such assistance  as  the  board  may
  reasonably request, to cooperate fully with investigations by the board,
  and  to  provide  to  the board upon request records and other materials
  which are necessary for the  investigation  of  any  matter  within  its
  jurisdiction  pursuant to this chapter, except such records or materials
  that cannot be disclosed by law.
    b. The police commissioner shall ensure that officers and employees of
  the police department appear before and  respond  to  inquiries  of  the
  board  in  connection  with  the  investigation of any matter within the
  board's jurisdiction  pursuant  to  this  chapter,  provided  that  such
  inquiries  are  conducted  in  accordance with department procedures for
  interrogation of members.