Former Minneapolis police officer Derek Chauvin was sentenced to more than 22 years in prison on Friday for the murder of George Floyd, whose death became a watershed moment in the national debate over race and policing.

The 270-month sentence handed down by Judge Peter Cahill was 10 years longer than state guidelines had suggested, despite the defence’s plea for leniency.

“This is not based on emotion or sympathy,” Cahill said during a hearing at the Hennepin county government centre in Minneapolis. “But at the same time I want to acknowledge the deep and tremendous pain of all the families, especially the Floyd family.”

The sentence, he told Chauvin, was based on his abuse of authority and “particular cruelty” to George Floyd.

Chauvin, 45, was found guilty in April after a six-week trial. The former Minneapolis police officer knelt on Floyd’s neck for more than nine minutes during an arrest as Floyd cried out numerous times that he could not breathe.

Chauvin said before sentencing that he could not give a full statement because of ongoing legal matters — he is likely to appeal — but offered condolences to the Floyd family.

During the sentencing hearing, Terrence Floyd wept as he told the court how his brother’s murder affected him.

“I wanted to know from the man himself — why? What was going through your head when you had your knee on my brother’s neck?” he said. “Why did you stay there?”

“On behalf of me and my family, we seek the maximum penalty,” he added. “We don’t want no more slaps on the wrist.”

Speaking via video, George Floyd’s 7-year-old daughter Gianna said that if she could speak to her father now she would tell him, “I miss you and I love you”.

Floyd’s death sparked protests for racial justice across the US and the world, after the incident was filmed and posted online. Darnella Frazier, who was 17 years old when she filmed the murder, was later honoured with a special citation by the Pulitzer Prize board.

The murder drew attention to the disproportionate number of killings of black Americans at the hands of police and sparked a broader dialogue about racial inequality throughout American society.

Police officers are rarely charged, let alone convicted of murder for killings committed while on duty. But a jury convicted Chauvin of second-degree murder, third-degree murder and second-degree manslaughter. He was only sentenced on the most serious charge.

Prosecutors had asked the judge for a 30-year sentence, while the defence asked for probation.

Carolyn Pawlenty, Chauvin’s mother, told her son that she continued to believe in his innocence and asked the court for leniency.

“The public will never know the loving and caring man he is, but his family does,” she said. “Derek has played over and over in his head the events of that day.”

Cahill wrote in a decision outlining his reasoning that “part of the mission of the Minneapolis Police Department is to give citizens ‘voice and respect’. Here, Mr Chauvin, rather than pursuing the MPD mission, treated Mr Floyd without respect and denied him the dignity owed to all human beings and which he certainly would have extended to a friend or neighbour.”

Three other officers were present at the time of Floyd’s death. The former officers — Alexander Kueng, Thomas Lane and Tou Thao — are set to be tried in March on charges of aiding and abetting murder.

Media outnumbered activists and observers outside the courthouse after the sentencing. But one man, Leon Lawson, had driven from Michigan with his 4-year-old son to be there. Lawson said his uncle had served more than 50 years for a murder committed as a youth. Two decades for Chauvin, he said, was not enough.

“I wanted my son to see our justice system upfront and in person,” he said. “To say he was here when the guy was sentenced, and to be able to compare the difference because of the skin colour . . . I guess this is a step in the right direction, so we’ll take what we can get.”

Attorney Benjamin Crump, who represented the Floyd family in a civil lawsuit against the city of Minneapolis, said on Friday that “one sentence does not solve a criminal justice problem”.