Former police officer Derek Chauvin won't testify in George Floyd murder trial

Defence lawyers for former police officer Derek Chauvin, who is accused of killing Black man George Floyd, have wrapped up their case without putting the defendant on the stand.

The defence wrapped up arguments on Thursday after presenting a total of two days of testimony, compared to the prosecution's two weeks.

Mr Chauvin informed the court he would not testify, saying he would invoke his Fifth Amendment right not to take the stand.

READ MORE: Expert blames George Floyd's death on heart rhythm problem

It would have been the first time Mr Chauvin publicly told his side of the story.

"Is this your decision not to testify?" Judge Peter Cahill asked.

"It is, your honour," the defendant said.

Some prosecution rebuttal testimony was expected to follow on Thursday (Friday AEST).

Closing arguments are set for Monday, after which the racially diverse jury will begin deliberating at the barbed-wire-ringed courthouse, with Minneapolis on edge against a repeat of the protests and violence that broke out last spring over Floyd's death.

The question of whether Mr Chauvin would testify was the subject of weeks of speculation.

The risks were high: testifying could have opened him up to devastating cross-examination, with prosecutors replaying the video of the arrest and forcing him to explain, one frame at a time, why he kept pressing down on Mr Floyd.

But taking the stand could have also given the jury the opportunity to see or hear any remorse or sympathy he might feel.

He would have been able to remove the COVID-19 mask he has had to wear at the defence table.

READ MORE: Expert says George Floyd died from a lack of oxygen

The only time Mr Chauvin has been publicly heard defending himself was when the jury listened to body-camera footage from the scene last May.

After an ambulance had taken Mr Floyd away, the former officer told a bystander: "We gotta control this guy 'cause he's a sizeable guy ... and it looks like he's probably on something."

The decision not to testify was announced a day after a forensic pathologist testifying for the defence said Mr Floyd died of a sudden heart rhythm disturbance as a result of his heart disease.

That contradicted prosecution experts who said Mr Floyd succumbed to a lack of oxygen from the way he was pinned down.

Dr David Fowler, a former Maryland chief medical examiner who is now with a consulting firm, said on Wednesday the fentanyl and methamphetamine in Mr Floyd's system, and possibly carbon monoxide poisoning from auto exhaust, were contributing factors in the 46-year-old Black man's death last May.

"All of those combined to cause Mr Floyd's death," he said.

Dr Fowler said he would classify the manner of death "undetermined," rather than homicide, as the county's chief medical examiner ruled.

He said Mr Floyd's death had too many conflicting factors, some of which could be ruled homicide and some that could be considered accidental.

Defence attorney Eric Nelson is trying to prove the 19-year Minneapolis police veteran did what he was trained to do and that Mr Floyd died because of his illegal drug use and underlying health problems.

Prosecutors say Mr Floyd died because the white officer's knee was pressed against Floyd's neck or neck area for 9 1/2 minutes as he lay on the pavement on his stomach, his hands cuffed behind him and his face jammed against the ground.

Mr Chauvin, 45, is charged with murder and manslaughter in Mr Floyd's death after his arrest on suspicion of passing a counterfeit $20 at a neighbourhood market.

The video of Mr Floyd gasping that he couldn't breathe as bystanders yelled at Mr Chauvin to get off him triggered worldwide protests, violence and a furious examination of racism and policing in the US.