George Floyd Officer Trial

In this image from video, Dr. Martin Tobin testifies as Hennepin County Judge Peter Cahill presides Thursday, April 8, 2021, in the trial of former Minneapolis police Officer Derek Chauvin at the Hennepin County Courthouse in Minneapolis, Minn. Chauvin is charged in the May 25, 2020 death of George Floyd.

MINNEAPOLIS (AP) — George Floyd died of a lack of oxygen from the way he was held down by police, a retired forensic pathologist testified Friday at former Officer Derek Chauvin's murder trial.

The testimony of Lindsey Thomas, who retired in 2017 from the Hennepin County Medical Examiner's office in Minneapolis, bolstered the findings of other experts on Thursday who rejected the defense theory that Floyd's drug use and underlying health problems killed him.

Thomas did not work on Floyd's case but agreed with her former colleague Hennepin County Medical Examiner Andrew Baker that Floyd died from cardiopulmonary arrest complicated by the way law enforcement restrained him and compressed his neck.

But she went further in saying "the primary mechanism of death is asphyxia, or low oxygen."

"This is a death where both the heart and lungs stopped working. The point is, it's due to law enforcement subdual, restraint and compression," Thomas said. "The activities of the law enforcement officers resulted in Mr. Floyd's death."

Thomas said she reached her conclusion primarily from the video, which showed Floyd "in a position where he was unable to adequately breathe."

The autopsy itself ruled out heart attack, aneurysm, COVID-19 and other factors, and Thomas said it was not a drug overdose death, either.

"There is no evidence to suggest he would have died that night except for the interactions with law enforcement," she said.

Baker was expected to testify later.

Thomas' testimony came a day after other medical experts also said Floyd died of a lack of oxygen.

"A healthy person subjected to what Mr. Floyd was subjected to would have died," 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, testified Thursday.

Tobin said the lack of oxygen resulted in brain damage and caused Floyd's heart to stop.

Chauvin, 45, is charged with murder and manslaughter in Floyd's death May 25 after kneeling on him for what prosecutors say was 9 1/2 minutes. 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.

Chauvin attorney Eric 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.

Floyd's death certificate listed other contributing conditions: narrowed arteries, high blood pressure, fentanyl intoxication and recent methamphetamine use. But Thomas said that they did not directly cause his death and that such factors are commonly included on death certificates to inform public health officials.

Instead, Floyd died because the position of his body — lying on his stomach, his hands cuffed behind his back and officers pressing their body weight into him — made it impossible to breathe, said Thomas, who called Floyd's death "so well-documented" because of extensive video evidence.

On Thursday, Tobin used easy-to-understand language and even loosened his tie to explain medical concepts, telling the jury that Floyd's breathing was severely constricted while Chauvin and two other Minneapolis officers held the 46-year-old Black man down.

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" more than 90% of the time.

He said several other factors also made it difficult for Floyd to breathe: officers lifting up on the suspect's handcuffs, the hard pavement, his prone position, his turned head and a knee on his back.

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%, after which "you are in deep trouble."

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

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Find AP's full coverage of the death of George Floyd at: https://apnews.com/hub/death-of-george-floyd