By Amy Forliti, Steve Karnowski and Tammy Webber

Associated Press

MINNEAPOLIS — George Floyd died of a lack of oxygen from being pinned to the pavement with a knee on his neck, a medical expert testified at former Officer Derek Chauvin’s murder trial Thursday, emphatically rejecting the defense theory that Floyd’s drug use and underlying health problems were what killed him.

“A healthy person subjected to what Mr. Floyd was subjected to would have died,” said prosecution witness Dr. Martin Tobin, a lung and critical care specialist at the Edward Hines Jr. VA Hospital and Loyola University’s medical school in Illinois.

Using easy-to-understand language to explain medical concepts and even loosening his necktie to illustrate a point, Tobin told the jury that Floyd’s breathing was severely constricted while Chauvin and two other Minneapolis officers held the 46-year-old Black man down on his stomach last May with his hands cuffed behind him and his face jammed against the ground.

The lack of oxygen resulted in brain damage and caused his heart to stop, the witness said.

Tobin, analyzing images of the three officers restraining Floyd for what prosecutors say was almost 9 1/2 minutes, testified that Chauvin’s knee was “virtually on the neck” for more than 90% of the time.

He cited several other factors that he said also made it difficult for Floyd to breathe: officers lifting up on the suspect’s handcuffs, the hard surface of the street, his prone position, his turned head and a knee on his back.

Chauvin kept his knee on Floyd’s neck for 3 minutes, 2 seconds, after Floyd had “reached the point where there was not one ounce of oxygen left in the body,” Tobin said.

As prosecutors repeatedly played a video clip of Floyd on the ground, Tobin pinpointed what he said was a change in the man’s face that told him Floyd was dead. That moment happened around five minutes after police began holding Floyd down.

“At the beginning you can see he’s conscious, you can see slight flickering, and then it disappears,” Tobin said. He explained: “That’s the moment the life goes out of his body.”

Chauvin, 45, is charged with murder and manslaughter in Floyd’s death May 25. Floyd was arrested outside a neighborhood market after being accused of trying to pass a counterfeit $20 bill. Bystander video of Floyd crying that he couldn’t breathe as onlookers yelled at the white officer to get off him sparked protests and scattered violence around the U.S.

In his testimony, Tobin explained that just because Floyd was talking and shown moving on video doesn’t mean he was breathing adequately. He said that a leg movement seen in the footage was involuntary, and that a person can continue to speak until the airway narrows to 15%, after which “you are in deep trouble.”

Officers can be heard on video telling Floyd that if he can talk, he can breathe.

During cross-examination, Chauvin attorney Eric Nelson pressed Tobin on that common misconception, pointing to earlier testimony that Minneapolis officers are trained that if people can speak, they can breathe.

Nelson has argued that Chauvin did what he was trained to do and that Floyd’s death was caused by illegal drugs and underlying medical problems. An autopsy found fentanyl and methamphetamine in his system. But Tobin said he analyzed Floyd’s respiration as seen on body-camera video and explained that while fentanyl typically cuts the rate of respiration 40 percent, Floyd’s breathing was “right around normal” just before he lost consciousness.