A US policeman charged with murdering George Floyd, the 46-year-old African American whose death in May sparked nationwide protests, appeared in court for the first time on Friday, along with three other officers implicated in the killing.

As scores of protesters outside the Family Justice Center in Minneapolis demanded justice, the four officers sought separate trials in the case, as court filings showed each seeking to pin the blame for Floyd's death on the others.

Derek Chauvin, charged with second and third-degree murder and manslaughter after being filmed pressing his knee to Floyd's neck until he died, claims a fentanyl overdose was the cause of the fatality, and accused two other officers of not correctly assessing Floyd's condition.

Prosecutors rejected the overdose claim as "ludicrous" and said all four - Chauvin, Thomas Lane, Alexander Kueng and Tou Thao - should be tried together based on "substantial evidence" that they "worked in close concert with one another" when Floyd was killed.

US policemen Derek Chauvin, Thomas Lane, Alexander Kueng and Tou Thao charged with murdering George Floyd, the 46-year-old African American whose death in May sparked nationwide protests, appeared in court for the first time on September 11, 2020 in Minneapolis. Photo: AFP

'Brutal and dehumanising' murder

Floyd's death on May 25 became a symbol of what many say is systemic racism and abuse of African Americans by police, and sparked protests across the country that continue under the banner of Black Lives Matter.

Prosecutors say Floyd's death was "vicious, brutal, and dehumanising." He had been detained for allegedly using a counterfeit $20 bill.

All four defendants say the decision to restrain Floyd, who was handcuffed and held down by two of the officers while under Chauvin's knee - was reasonably justified.

The officers were all fired one day after Floyd's death, reflecting the growing seriousness with which US cities are beginning to take police abuse allegations.

Lane, Kueng and Thao face charges of aiding and abetting second-degree murder and manslaughter.

District Court Judge Peter Cahill rejected a defence lawyer's move to introduce evidence into the trial that during a May 2019 arrest in Texas, Floyd swallowed drugs to avoid being charged.

The defence is suggesting, but has not revealed evidence, that Floyd did the same in the May 25, 2020 incident.   

Black Lives Matter

Protesters gathered outside the courthouse in downtown Minneapolis ahead of the hearing, chanting "George Floyd" and carrying placards and a large flag that read 'Black Lives Matter'.

The hearing focused on the difficulty of providing a safe and fair jury trial, scheduled to begin in March 2021, given the massive publicity to the case, which has inflamed opinions on both the right and left sides of the political spectrum.

As the defendants, their lawyers and prosecutors all wore safety masks, the court wrestled over how to seat a jury given the threat of COVID-19, and what defence lawyers said are constant threats over phone and social media that could poison a fair trial.

Jury selection usually involves parading dozens of candidates through a courtroom for live questioning by lawyers from both sides to determine if they are already biased.

Cahill proposed to send questionnaires to potential jurors at their homes.

But defence attorneys said that risks them being able to look up the case on the internet and form opinions before they reply to the questions.

Meanwhile, the judge put off, for the time being, a motion by defence lawyers to move the case to another jurisdiction, saying a fair trial in Minneapolis was impossible.

After the hearing, Ben Crump, an attorney for Floyd's family, accused the defendants of falling back on tactics of smearing Floyd's image to justify his death.

It is "a blatant attempt to kill George Floyd a second time: They kill a person and then assassinate his character," Crump said.

"The only overdose that killed George Floyd was an overdose of excessive force and racism by the Minneapolis Police Department," he said.

People gather outside the family justice center during a press conference. Photo: AFP