Minneapolis, Feb 7 (AP) George Floyd died because his breathing was restricted as he was restrained while handcuffed and facedown, a lung expert testified Monday at the federal trial of three former Minneapolis police officers charged with violating Floyd's civil rights.

Dr. David Systrom, a pulmonologist and critical care physician at Brigham and Women's Hospital in Boston, said Floyd's upper airway was compressed by Officer Derek Chauvin's knee, while his position on the hard asphalt with his hands cuffed behind his back did not allow his lungs to expand, cutting off the flow of oxygen.

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“Oxygen delivered to the heart and brain is critical to survival,” Systrom said. J. Alexander Kueng, Thomas Lane and Tou Thao are accused of depriving Floyd, 46, of his rights when they failed to give him medical aid as Chauvin knelt on the Black man's neck for 9 1/2 minutes while Floyd pleaded for air.

Kueng and Thao are also accused of failing to intervene in the May 2020 killing that triggered protests worldwide and a reexamination of racism and policing.

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Kueng knelt on Floyd's back, Lane held his legs and Thao kept bystanders back.

Their trial resumed Monday after being abruptly suspended last week because one defendant tested positive for COVID-19.

Systrom is the second medical expert called to testify by prosecutors.

Last week, Dr. Andrew Baker, Hennepin County's chief medical examiner, said Floyd died after police “subdual, restraint and neck compression” caused his heart and lungs to stop.

He said heart disease and drug use were factors but not the “top line” causes. He said Floyd had an enlarged heart that needed more oxygen than normal, as well as narrowed arteries.

Testimony began Jan. 24 after a jury was selected in one day.

Kueng, who is Black, Lane, who is white, and Thao, who is Hmong American, are charged with willfully depriving Floyd of his constitutional rights while acting under government authority. The charges allege that the officers' actions resulted in Floyd's death.

Chauvin was convicted of murder and manslaughter in state court last year and pleaded guilty to a federal civil rights charge. He remains in prison.

Lane, Kueng and Thao also face a separate state trial in June on charges alleging that they aided and abetted murder and manslaughter.

All three have been free on bail since shortly after they were charged in June 2020. (AP)

(The above story is verified and authored by Press Trust of India (PTI) staff. PTI, India’s premier news agency, employs more than 400 journalists and 500 stringers to cover almost every district and small town in India.. The views appearing in the above post do not reflect the opinions of LatestLY)