Inspector Bradstreet A Highly Respected Police Detective With 25 Years Of Investigative Experience

Riddle: Inspector Bradstreet, a highly respected police detective with 25 years of investigative experience on the force, was in a room with four homicide suspects: Joan, Shirley, Dorothy, and Irene. He was in the room with the four of them for at least 15 minutes, but for some reason, he had not started interrogating the suspects, despite the fact that a dead body, which had a knife sticking out of its back, lay on the floor in the room with them. One of the four suspects had called 911 to summon the police at some point. Why hadn't this highly decorated and respected detective started his investigation into the obvious murder by questioning the four suspects? For what reason was he waiting?