Minneapolis (AFP) - Minneapolis residents were bracing Sunday for the opening of what is sure to be one of the nation's most closely watched trials in years -- that of the white policeman charged with killing George Floyd, a Black man whose dying struggles were captured on a video seen around the world.

Derek Chauvin -- the now former city officer who used his knee to pin a pleading, gasping Floyd by the neck to the pavement for nearly nine minutes -- faces second-degree murder and manslaughter charges in the Hennepin County district court.

Floyd's death laid bare already sore racial wounds in the United States, sparking months of sometimes violent protests against racial injustice and police brutality, both in the US and abroad.

Jury selection begins at 9:00 am (1500 GMT) Monday, as lawyers for both sides face the difficult task of finding jurors who, in the intensely publicized case, have not already made up their minds about Chauvin's guilt.

The process is expected to take up to three weeks, with arguments slated to begin on March 29.

But protesters were already gathering near the courthouse on Sunday, with many holding up "Black Lives Matter" placards and demanding "justice for George Floyd."

Chauvin's case promises to be extraordinary: it will feature star attorneys, be held under tight security and be livestreamed.

It will also be intensely watched as a potential marker of change in a country that recently elected its first Black vice president, but where police officers historically have often escaped punishment for abusive acts.

It will feature gripping testimony, as foreshadowed Sunday by Benjamin Crump, a prominent civil rights attorney representing the Floyd family.

"You look at the video, and you hear him say 28 times, 'I can't breathe,'" Crump told ABC's "This Week." 

"The public is begging the police to take the knee off his neck. They say his nose is bleeding; he can't breathe; he is going unconscious -- you're going to kill him."

Amid the Covid-19 pandemic, social distancing rules mean seating will be limited, with the Floyd and Chauvin families allowed only one seat a day. 

Despite intense global interest, only two reporters will be allowed in each day, with scores of others watching monitors from a nearby building.

The Minnesota attorney general's office brought in Neal Katyal, a former US acting solicitor general who has argued cases before the Supreme Court, to help with the prosecution.

Ashley Heiberger, a former police officer who now works as an advisor on police practices, said: "The fact that a police officer has been charged criminally for an abusive use of force, that in and of itself is an outlier."

"It's even rarer for them to be convicted." 

The circumstances surrounding 44-year-old Chauvin's case, however, are so troubling that "to the best of my knowledge, no police officers or police organizations came out and defended his action," Heiberger said.

Three other police officers involved in Floyd's arrest -- Alexander Kueng, Thomas Lane and Tou Thao -- face lesser charges and will be tried separately.

All four officers were fired by the Minneapolis Police Department.

Floyd's arrest was prompted by accusations that he tried to pass a counterfeit $20 bill in a nearby store.

'Exactly as he was trained to do'

Chauvin, a 19-year veteran of the force, was released from prison on bail in the fall and is expected to plead not guilty to the murder and manslaughter charges.

"Mr. Chauvin acted according to MPD policy, his training and within his duties as a licensed peace officer of the State of Minnesota," according to his lawyer, Eric Nelson. "He did exactly as he was trained to do."

According to Nelson, Floyd died of an overdose of fentanyl. 

An autopsy did find traces of the drug in Floyd's system but said the cause of death was "neck compression."

It will take a unanimous verdict by the 12-member jury to put Chauvin behind bars for what could be a long prison sentence.

A hung jury could give rise to another wave of anti-racism demonstrations.

The authorities have mobilized thousands of police officers and members of the National Guard to provide security.

The courthouse where the trial will take place currently resembles an armed camp, surrounded by concrete barriers and barbed-wire fencing.

Prospective jurors have been presented with a 16-page questionnaire.

"How favorable or unfavorable are you about Black Lives Matter?" is one of the questions.

"Have you ever watched video of George Floyd's death?" is another. "If yes, how many times?"

A verdict is not expected until late April.