“The ability to speak does not mean the patient is without danger,” said Dr. Mariell Jessup, chief science and medical officer of the American Heart Association.

“To speak, you only have to move air through the upper airways and the vocal cords, a very small amount,” and that does not mean that enough air is getting down into the lungs where it can supply the rest of the body with oxygen, said Dr. Gary Weissman, a lung specialist at the University of Pennsylvania.

The false perception that someone who can speak can also take in enough air is not part of any known police training curriculum or practices, according to experts on police training and use of force.

“I’m not aware of any standard training of police officers that lets them know, ‘Hey, if someone is still able to talk they are not having difficulty breathing, so you can just keep doing what you are doing,'” said Craig Futterman, professor at University of Chicago Law School and an expert on use of force.