The three white men convicted of murdering Ahmaud Arbery, an unarmed 25-year-old black man, in the US state of Georgia, have asked for a new trial.

Greg McMichael and his son Travis McMichael were sentenced to life in prison without parole over the killing, while their neighbour William Bryan received a life sentence with the possibility of parole.

Their attorneys returned on Thursday before the judge who handed down their sentences to argue, among other things, that the jury had been tainted.

The trio have already appealed against a federal hate crimes verdict against them.

Arbery was fatally shot by the younger McMichael in February 2020 while jogging through the neighbourhood of Satilla Shores in Glynn County, Georgia.

As he ran past their home, the father and son chased after him in pickup trucks.

Bryan, who joined the pursuit, went on to record cell phone video of Travis McMichael firing shotgun blasts at close range into Arbery in the street.

The men have argued they believed Arbery was a thief and wished to detain him before police arrived, but no evidence was ever found that the jogger had committed any crimes in the area.

No arrests were made in the case for more than two months until neighbour Bryan’s footage was leaked online.

Arbery’s name then turned into a rallying cry as part of a broader racial justice reckoning in America, related to the recent deaths of two other black people, Breonna Taylor and George Floyd.

On Thursday, the only black person on the trial’s jury panel was called to the stand and questioned over whether he “concealed his bias in favour of the Arbery family” during jury selection.

That assertion by defence lawyers was made in light of interviews the juror gave to a private investigator in 2022, in which he allegedly said: “I felt like the weight of the whole black race was on my shoulders”.

Though he was not asked about that comment, the man – identified only as Juror no. 380 – testified: “I felt sorry for the family. After court started, I felt sorry for both sides. I wanted to help for the truth to come out, right from wrong.”

During jury selection, defence lawyers rejected eight other black panellists.

But Travis McMichael’s attorney, Pete Donaldson, conceded in court on Thursday that he expected the motion for retrial to fail but nevertheless wanted to “have it on the record” to set up an appeal to the US Supreme Court.

Arbery’s father, Marcus Arbery Sr, told reporters outside the court that the arguments were “very weak”.

“They were throwing everything to the wall, and nothing will stick,” he said.

Superior Court Judge Timothy Walsmley is allowing a month or more for both legal teams to file briefs summing up their arguments before he issues a decision.