Cooper revealed she gave paramedics who raced to the singer's rented Holmby Hills, Los Angeles home the authorisation to pronounce the Thriller singer dead.
However, Conrad Murray - who found the star's lifeless body in his bedroom - insisted they try to resuscitate the King of Pop for almost an hour.
Cooper told the court on Thursday (06Jan11) she authorised paramedics to pronounce Jackson dead at 12.57pm on 25 June, 2009, but they declined at Murray's request - and because of the singer's celebrity.
Cooper officially pronounced Jackson dead at 2.26pm after the singer's body arrived at the hospital.
Conrad Murray's girlfriend Nicole Alvarez, who the doctor called from the ambulance to UCLA, has been ordered to appear in court on Friday (07Jan11). The preliminary hearing began on Tuesday (04Jan11) and is expected to last two weeks.