Dr. David Fowler, a medical expert for the defence in the murder trial of Derek Chauvin, says he believes George Floyd's death during his arrest was the result of heart disease, and exhaust fumes may have possibly played a role.

Defence attorney Eric Nelson (left) and defendant, former Minneapolis police officer Derek Chauvin listen, on April 14, 2021, as judge Peter Cahill presides over motions in the trial of Chauvin.
Defence attorney Eric Nelson (left) and defendant, former Minneapolis police officer Derek Chauvin listen, on April 14, 2021, as judge Peter Cahill presides over motions in the trial of Chauvin. (AP)

George Floyd died of a sudden heart rhythm disturbance as a result of his heart disease, a forensic pathologist has testified for the defence at former Officer Derek Chauvin's murder trial, contradicting experts who said the Black man succumbed to a lack of oxygen from the way he was pinned down.

Dr. David Fowler, a former chief medical examiner for the state of Maryland and now a member of a consulting firm, said on Wednesday the fentanyl and methamphetamine in Floyd's system, and possible carbon monoxide poisoning from auto exhaust, were contributing factors in the 46-year-old man's death last May.

Prosecutor Jerry Blackwell launched an aggressive cross-examination, attacking Fowler's findings down the line.

He got Fowler to acknowledge that even someone who dies from being deprived of oxygen ultimately dies of an arrhythmia.

Fowler appeared to dispute at least some of the findings of Hennepin County's chief medical examiner, who ruled Floyd's death a homicide. Fowler said he would fall back to an "undetermined" ruling.

READ MORE: Defence begins for officer charged with murdering George Floyd

Fowler's testimony attacked

He also got Fowler to admit that he didn't take the weight of Chauvin's gear into account when he analysed the pressure on Floyd's body.

He also all but accused Fowler of jumping to conclusions and suggesting to the jury that Floyd had a white pill in his mouth in the video of his arrest.

Fowler denied saying that.

Blackwell also attacked Fowler's testimony about carbon monoxide, which displaces oxygen in the bloodstream of people who breathe it in.

Blackwell also got Fowler to agree that it would take four minutes to cause irreversible brain damage if the brain is starved of oxygen, and that insufficient oxygen can cause the heart to stop.

"And if a person dies as a result of low oxygen, that person is also going to die ultimately of a fatal arrhythmia, right?" Blackwell asked.

Fowler responded: "Correct. Every one of us in this room will have a fatal arrhythmia at some point."  

Fowler further agreed that Floyd should have been given immediate attention when he went into cardiac arrest because there still was a chance to save him at that point.

Request to acquit Chauvin rejected

A number of medical experts called by prosecutors have said Floyd died from a lack of oxygen because the way he was restrained restricted his breathing.

Chauvin, a 45-year-old white man, is on trial on charges of murder and manslaughter in Floyd's death after his arrest on suspicion of passing a counterfeit $20 at a neighborhood market.

The video of him as he gasped that he couldn't breathe touched off worldwide protests, violence and a furious examination of racism and policing in the US.

The defence hasn't said whether Chauvin will take the stand.

Earlier on Wednesday, Judge Peter Cahill turned down a defence request to acquit Chauvin, rejecting claims that prosecutors failed to prove Chauvin's actions killed Floyd. 

Requests for an acquittal are routinely made midway through a trial and are usually denied.

READ MORE: George Floyd's girlfriend tells jury of couple's struggle with addiction

Source: AP