Section 927. General duties of district attorneys

It shall be the duty of
  the district attorney of the respective counties  of  New  York,  Bronx,
  Kings,  Queens  and  Richmond  to  prosecute  all  crimes  and  offenses
  cognizable by the courts of the county for  which  he  shall  have  been
  elected or appointed, except when the place of trial of an indictment is
  changed from one county to another, it shall be the duty of the district
  attorney  of  the  county  where  the indictment is found to conduct the
  trial of the indictment so removed, but  said  district  attorney  shall
  assist  in  the  trial of an indictment removed to his county for trial,
  upon request  of  the  district  attorney  of  the  county  wherein  the
  indictment  was found. He shall perform the duties prescribed in section
  seven hundred of this chapter and such other duties as are prescribed by
  law.