The death sentence had originally been sought by the Obama administration, and the appeal was filed by the Trump administration.
Biden has pledged to seek an end to the federal death penalty, but he has said nothing about how he plans to do so.
The case won't be heard until the springtime (NZ), and it's unclear how the new administration will approach Tsarnaev's case.
"It may be that the legal issue, about just how carefully district courts in capital cases have to screen prospective jurors, is one that the current Justice Department wants the justices to clarify even if it has no intention of carrying out a potential death sentence down the road", Vladeck said. The Chechen immigrant was convicted of more than two dozen crimes in 2015, and a court imposed six death sentences and 11 concurrent life sentences.
White House press secretary Jen Psaki told reporters Biden "has grave concerns about whether capital punishment as now implemented is consistent with the values that are fundamental to our sense of justice and fairness", and "has also expressed his horror at the events of that day and Tsarnaev's actions". But the appeals panel noted that Tsarnaev, who told the courtroom on the day of his sentencing that he was "guilty of this attack", would remain in prison for the rest of his life regardless of whether the death sentence is imposed.
A jury sentenced Tsarnaev to death by lethal injection in 2015, but this was overturned past year by an appeals court.
The government asked the court to take up the case when President Donald Trump was in office, and his Department of Justice was aggressive in restarting the federal death penalty.
Tamerlan, 26, died following a gunfight with police and being run over by his brother as he fled.
Tsarnaev, now 27, was convicted of all 30 charges against him, including conspiracy and use of a weapon of mass destruction and the killing of a university police officer during the Tsarnaev brothers' getaway attempt.
Appeals Court Judge Juan Torruella, who died late past year, wrote that the district court judge had relied on "self-declarations of impartiality" by prospective jurors, some of whom admitted before the trial that they were convinced Tsarnaev was guilty.
The U.S. Supreme Court on Monday agreed to hear the federal government's bid to reinstate Boston Marathon bomber Dzhokhar Tsarnaev's death sentence for helping carry out the 2013 attack that killed three people and wounded more than 260 others.
The U.S. Supreme Court has granted the Justice Department's request to review a lower court's decision that vacated the death sentence of Boston Marathon bomber Dzhokhar Tsarnaev.