Updated 10pm

Former policeman Derek Chauvin was sentenced to 22-and-a-half years in jail Friday for murdering African American George Floyd, a killing that sparked America's biggest demonstrations for racial justice in decades.

"The sentence is not based on emotion or sympathy," said Judge Peter Cahill, handing down the term at a Minneapolis court after prosecutors sought a 30-year sentence.

He added in a short address that it was also not based on "on public opinion," but on the law and the facts specific to the case.

During a sentencing hearing earlier, the victim's brother said Chauvin should receive the maximum sentence of 40 years. The ex-cop offered "condolences" to the family.

Minnesota law provides for a minimum sentence of 12.5 years for the white, 45-year-old killer, who has been behind bars since being convicted on three counts of murder and manslaughter two months ago in relation to the death of Floyd, who was African American.

But an emotional Terrence Floyd told a Minneapolis court that Judge Peter Cahill should hand Chauvin the stiffest term possible.

His voice choking, Floyd also urged Chauvin to explain the reason for the murder during an arrest in May last year, a killing that sparked America's biggest demonstrations for racial justice in decades.

"Why? What were you thinking? What was going through your head when you had your knee on my brother's neck?" said Floyd.

Before his impact statement, the court watched a moving video from the late Floyd's seven-year-old daughter Gianna Floyd.

"I miss you and I love you," the girl said, when asked in the recorded message what she said would say to her father today.

Chauvin, wearing a light grey suit, made a short statement in which he said he wanted to "give my condolences to the Floyd family."

"There's going to be some other information in the future that would be of interest and I hope things will give you some peace of mind," he added.

Earlier, Chauvin's mother Carolyn Pawlenty described her son as "a good man," insisting he was innocent.

Judge Cahill has identified aggravating circumstances that could signal a heavy punishment.

He said Chauvin had "abused his position of trust and authority," treated Floyd with "particular cruelty" in front of minors and "committed the crime as a group with the active participation of at least three other" officers.

Chauvin and three colleagues arrested Floyd, 46, in May last year on suspicion of having passed a fake $20 bill in a store in Minneapolis, a northern city of around 420,000. They handcuffed him and pinned him to the ground in the street.

Chauvin then knelt on the back of Floyd's neck for nearly 10 minutes, indifferent to the dying man's groans and to the pleas of distraught passers-by.

The scene, filmed and uploaded by a young woman, quickly went viral. After weeks of home confinement due to the COVID-19 pandemic, hundreds of thousands of people poured onto streets across the country and overseas, to demand an end to racism and police brutality. 

It took weeks for the mass demonstrations to taper off, but the debate around the pressing social issues remains vivid in the United States, where President Joe Biden has been slow to come up with the police reforms he promised during his campaign.

Late Thursday, Republican and Democratic lawmakers announced that after weeks of negotiations they had come up with "an agreement on a framework addressing the major issues for bipartisan police reform."

'Particularly cruel'

Chauvin's trial was closely followed by millions across the country. 

The sacked police officer, who was present for the full six weeks of his trial, did not testify. His lawyer said he had followed police procedures in force at the time and that Floyd's death was due to health problems exacerbated by drug use.

The jurors were not convinced and took less than 10 hours to convict. Their decision was greeted with a huge sigh of relief across the country -- many had feared an acquittal would lead to worse unrest, while others worried that once again a white police officer would get away with what they saw as murder.

On Friday, additional law enforcement and fencing were present in downtown Minneapolis but gone were the National Guard soldiers and military vehicles seen during the trial.

Pre-sentencing, Chauvin's lawyer Eric Nelson pleaded that his client made "an error in good faith" and requested a reduced sentence to time already served, which would allow his client to be released immediately.

But the prosecution cited Chauvin's "particularly cruel" conduct and called for 30 years.

With good behaviour, he could serve just two-thirds of any prison sentence, with the remaining third on supervised release. 

Whatever the decision, the defecse will appeal the verdict, Nelson has said, citing doubts over the impartiality of some jurors.

On the eve of sentencing, the judge denied the defence's request for a new trial. 

Neither will the case end with Chauvin: his three former colleagues will face trial in March 2022 on charges of complicity in homicide. 

In parallel, the four men also face federal charges of violating Floyd's constitutional rights. No date has yet been set for that trial.