Speaking about the causes of George Floyd's death during the trial of police officer Derek Chauvin, an expert Thursday confirmed that Floyd died "due to low oxygen level" after Chauvin knelt on his neck for nearly 10 minutes. 

George Floyd repeatedly repeated "I can't breathe" to the three officers who held him to the ground after they cuffed his hands behind his back and pressed his back, neck and ribs.

Martin Toban, a doctor who specializes in respiratory diseases, who was asked by the prosecution to testify, said that a combination of these factors led to the death of the victim, as he was stuck between the ground and the force exercised by the police.

"With every breath, he was trying to get as much oxygen as possible because of the pressure the police put on his neck," he explained to the jury.

"The low oxygen level caused by breathing difficulties damaged his brain and caused an irregular heartbeat and a heart attack," he added.

The autopsy report stated that he had suffered a heart attack.

The expert said, "Anyone in good health would have died had he been exposed to what George Floyd had been exposed to."

Doctor Bill Smock, who was summoned by the prosecution, ruled out the hypothesis of a drug-related death, as Derek Nelson, a lawyer for Derek Chauvin, claimed.

Tests confirmed the presence of methamphetamine and fentanyl, a powerful narcotic, in George Floyd's blood.

According to Nelson, Floyd may have taken fentanyl before his arrest, which caused him breathing difficulties while he had Covid-19.

Chauvin, who could face a 40-year prison sentence, has pleaded not guilty, asserting that he used a technique identical to the training he received to control an uncooperative suspect.

The hearings are expected to continue for an additional two weeks, and the verdict in this case will be issued at the end of April.

The other three police officers will be tried for complicity in the killing.