The justices, by a 6-3 vote Friday, agreed with the Biden administration's arguments that a federal appeals court was wrong to throw out the sentence of death a jury imposed on Tsarnaev for his role in the bombing that killed three people near the finish line of the marathon in 2013.
The First US Circuit Court of Appeals in Boston ruled in 2020 that the trial judge improperly excluded evidence that could have shown Tsarnaev was deeply influenced by his older brother, Tamerlan, and was somehow less responsible for the carnage.
The appeals court also faulted the judge for not sufficiently questioning jurors about their exposure to extensive news coverage of the bombing. Retiring justice Judge Stephen Bryer led the dissent.
Tsarnaev played a vital role in the 2013 attack that killed three people and wounded more than 260 when twin blasts caused by bombs in pressure cookers were placed inside backpacks left near the finish line of the marathon.
Despite President Joe Biden's stated goal to eliminate capital punishment at the federal level, his administration opted to carry out an appeal — initially launched by the Justice Department under his predecessor Donald Trump — of a lower-court ruling overturning Tsarnaev's death sentence.
Lawyers for Tsarnaev, a US citizen who immigrated from the former Soviet Union as a child, have claimed that his brother was the more culpable of the two, saying Dzhokhar had no history of violence.
No federal inmates had been executed for 17 years before Mr Trump oversaw 13 executions in the last six months of his term.