An expert witness testified that loss of oxygen caused George Floyd’s death.

Witness rejects drug use, health as factors in death of Floyd

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

Tobin told the jury that Floyd’s breathing was severely constricted while Chauvin and two other Minneapolis officers held the 46-yearold 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 also testified that just because Floyd was talking and can be seen moving on video doesn’t mean he was breathing adequately. He said a leg movement seen in the footage was an involuntary sign of a fatal brain injury, and that a person can continue to speak until the airway narrows to 15 percent, 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, including high blood pressure and heart disease. An autopsy found fentanyl and methamphetamine in his system.

Another prosecution witness, Dr. Bill Smock, an expert on deaths from asphyxia, backed up Tobin’s assessment. Smock said Floyd did not have symptoms of a fentanyl overdose such as constricted pupils and decreased breathing. He said Floyd’s actions were the opposite, because he was pleading for air.

On cross-examination, Nelson questioned Smock about Floyd’s history of heart disease, getting Smock to agree that a struggle with police could put stress on the heart and that shortness of breath could be a sign of a heart attack.

But when questioned again by the prosecution, Smock said there was no evidence that Floyd had a heart attack or sudden death from arrhythmia, saying his death was caused by a gradual decrease of oxygen over several minutes “because of the pressure being applied to his back and neck.”

Also Thursday, a forensic toxicologist said that he tested blood drawn from Floyd at the hospital, as well as urine from his autopsy, and found a “very low” amount of methamphetamine. Daniel Isenschmid said fentanyl and a byproduct of its breakdown also were in Floyd’s system.

On cross-examination, Nelson suggested there was no way to know how much fentanyl Floyd had ingested, and Isenschmid agreed. The defense attorney also said it’s impossible to know the concentration of fentanyl in street drugs.