"There's a widespread perception in the American public, and particularly within law enforcement, that officers are more threatened, more endangered, more often assaulted, and more often killed than they have been historically," says Seth Stoughton, a law professor at the University of Southern Carolina and former policeman.
"I think it's a very strong perception. People truly believe it. But factually, looking at the numbers, it's not accurate," he says.
FBI data on police officers "feloniously killed" - killed as a result of a criminal act - indicates that the numbers have been falling, he says.