Former officers Tou Thao, Thomas Lane and J Alexander Kueng stand accused of violating Mr Floyd's civil rights by failing to administer medical aid to him. Kueng and Thao are also charged with failing to intervene when Derek Chauvin knelt on Mr Floyd's neck for more than nine minutes.

Both counts allege the officers' actions resulted in Mr Floyd's death.

The viral video footage of the killing shows Kueng kneeling on Mr Floyd's back and Lane holding down his legs. Thao is seen keeping bystanders from intervening.

What happens today - and what are prosecutors trying to prove?

Opening arguments will be heard today, and Judge Paul Magnuson has told the court the trial could last for about a month.

Prosecutors will try to prove that all three defendants willingly denied Mr Floyd his constitutional rights - by depriving him of his liberty without due process of law.

Lawyer Ben Crump, who represents Mr Floyd's family, tweeted: "Derek Chauvin's knee was on George Floyd's neck, but the other three officers aided and abetted in his death. They could have saved Floyd's life. They must ALSO be held responsible for their inaction!"

Chauvin is not facing trial on these charges as he pled guilty to them in December, months after his conviction for murder and manslaughter.

He was initially sentenced to 22.5 years and could now face more time behind bars as a result of this latest guilty plea.

What will the defence argue?

Rachel Paulose, a former US attorney for Minnesota, said it is "highly likely that the remaining three officers are going to point the finger at Derek Chauvin and try to absolve themselves of any liability by claiming that he alone was responsible for the abuses against Mr Floyd that resulted in his murder."

While harsh sentences are rarely brought in these federal civil rights cases, a guilty conviction could mean life imprisonment or the death penalty.

"At a minimum, it appears that these officers are facing 27 months in prison," according to Ms Paulose, "but of course, it could go all the way up to life. A lot will ultimately depend on which officer is found guilty of what counts, as well as the need to balance their sentences against that of Mr Chauvin."

How unusual are these charges?

These types of federal civil rights cases are rare.

According to data from Syracuse University, in 2019 these charges only represented a minute fraction of prosecutions brought - 27 out of every 100,000 prosecutions, or 0.027%.

The fact this case is even going to trial is indicative of progress, Ms Paulose says: "I think 10 years ago, this crime might not have even been charged, but I think the public, the Justice Department and even officers themselves are acknowledging the limits of reasonable force.

"It should be possible to detain a non-violent person without killing that person. I think that's fundamental to our sense of justice, and I think that's one of the many reasons this case caused so much outrage in the United States and around the world."

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This is the first of two trials the three former police officers will face this year. They're also charged in a Minnesota state court with aiding and abetting the murder and manslaughter of Mr Floyd.

That trial is scheduled to start on 13 June.