Prosecutors on Wednesday levelled new criminal charges against four Minneapolis police officers implicated in the death of an unarmed black man who was pinned by his neck to the street during an arrest caught on video, sparking nine days of nationwide protest and civil turmoil.

Derek Chauvin, arrested Friday on charges of third-degree murder and manslaughter in the death of George Floyd, 46, was newly charged with an additional, more serious count of second-degree murder, according to court documents filed in the case.

Former Minnesota police officers (clockwise from top left) Derek Chauvin, Tou Thao, Thomas Lane and J. Alexander Kueng poses in a combination of booking photographs from the Minnesota Department of Corrections and Hennepin County Jail in Minneapolis, Minn
Former Minnesota police officers (clockwise from top left) Derek Chauvin, Tou Thao, Thomas Lane and J. Alexander Kueng poses in a combination of booking photographs from the Minnesota Department of Corrections and Hennepin County Jail in Minneapolis, Minnesota, U.S. Minnesota Department of Corrections and Hennepin County Sheriff's Office/Handout via REUTERS

The added charge, defined under Minnesota law as unintentionally causing another person's death in the commission of a felony offence, can carry a sentence of up to 40 years, 15 years longer than the maximum sentence for third-degree murder.

'Please, I can't breathe'

Chauvin, 44, was the white officer seen in widely circulated video footage kneeling on Floyd's neck for nearly nine minutes as Floyd gasped for air and repeatedly groaned, "Please, I can't breathe," before growing motionless while bystanders shouted at police to let him up.

Floyd, whom police suspected of trying to pass a counterfeit bill to pay for cigarettes, was pronounced dead at a hospital shortly after the fatal encounter on May 25.

Three fellow officers dismissed from the Minneapolis police department along with Chauvin the following day were charged on Wednesday for the first time in the case - each with aiding and abetting second-degree murder and with aiding and abetting manslaughter.

Those three - Thomas Lane, J. Alexander Kueng and Tou Thao - have also been taken into custody. Aiding and abetting second-degree murder carries the same maximum punishment as the underlying offence - 40 years in prison.

George Floyd
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Floyd's death has become the latest flashpoint for long-simmering rage over police brutality against African Americans, propelling the highly charged issue of racial justice to the top of the political agenda five months before the U.S. presidential election on Nov. 3.

Scenes of protesters of all races flooding the streets - mostly peaceful but sometimes accompanied by arson, looting and clashes with police - have fueled a sense of crisis but also hopes of change. The mass public activity followed weeks of lockdown due to the coronavirus pandemic, which forced millions of Americans out of work and disproportionately affected minorities.

Trial months away

Minnesota Attorney General Keith Ellison, a black former U.S. congressman, has requested bail of $1 million for each of the four former officers, court documents showed.

When reached by Reuters over the phone, Lane's attorney, Earl Gray, said he had not received any information on the charges yet. Attorneys for the other officers charged in the case did not immediately respond to requests for comment.

"This is a significant step forward on the road to justice, and we are gratified that this important action was brought before George Floyd's body was laid to rest," Benjamin Crump, attorney for the Floyd family, said in a statement.