(CNN) The Supreme Court on Friday upheld the death sentence of Dzhokhar Tsarnaev, one of the two brothers responsible for the 2013 Boston Marathon bombing which led to the deaths of three spectators and a police officer, reversing a lower court decision.
The ruling was 6-3 along conservative-liberal lines.
"Dzhokhar Tsarnaev committed heinous crimes," Justice Clarence Thomas wrote for the majority. "The Sixth Amendment nonetheless guaranteed him a fair trial before an impartial jury. He received one."
The justices' ruling reversed a federal appeals court that in 2020 had wiped away the death sentence for Tsarnaev and ordered a new penalty-phase trial. At the time, the lower court said that Tsarnaev would remain in prison for the rest of his life for an "unspeakable brutal act," but that the trial court had made mistakes regarding issues related to pretrial publicity, as well as the exclusion of evidence that might have helped Tsarnaev's case.
Tsarnaev was convicted in 2015 in the deaths of Krystle Campbell, Martin Richard and Lingzi Lu at the marathon and Massachusetts Institute of Technology police officer Sean Collier several days later, among other charges. Hundreds were injured after Tsarnaev and his brother Tamerlan set off two shrapnel bombs near the finish line, leaving the sidewalks strewn with BBs, nails, metal scraps and glass fragments.
Tamerlan would later die in a gunfight with police, but Dzhokhar is being held in federal prison in Florence, Colorado, following his guilty verdict.
The Trump administration had initially asked the Supreme Court to step in and reinstate the original sentence. The Biden administration renewed the request, calling Tsarnaev a "terrorist" who acted in "furtherance of Jihad" and urging the justices to restore the jury's recommendation of death after the "carnage at the finish line."
It is unclear whether Tsarnaev would actually be put to death given the Biden administration's position on the federal death penalty. Currently, there is a moratorium on federal executions as the government studies the issue. Over the years, survivors and family members have split on whether Tsarnaev should get the death penalty.
Ginger D. Anders, a lawyer for Tsarnaev, had argued that there is no dispute that the bombings were a "grievous and shocking act of terrorism" but she said the lower court made two "serious errors" that compromised safeguards needed to ensure that her client received an appropriate penalty.
Anders sought to compel discovery about an unsolved triple murder that had occurred in 2011 in Waltham, Massachusetts. Investigators came to suspect a friend of Tamerlan, Ibragim Todashev, as being involved in the crime. Todashev initially denied involvement to agents but eventually asked for a deal. He said he had been involved but that Tamerlan had actually committed the murders by slitting the throats of the victims. Todashev had begun to write a confession but then attacked the agents who shot and killed him.
Anders sought to include the evidence because she argued it supported the proposition that her client did not deserve the death penalty, because he was only acting under the direction of his older brother who played a much greater role in executing the bombings at the marathon, as evidenced by his past experience.
Justice Stephen Breyer, writing for his liberal colleagues, Justice Elena Kagan and Sonia Sotomayor, said in dissent on Friday that they believed the evidence should have been heard by the jury.
"This is much stronger evidence of Tamerlan's capacity to influence than any evidence that the jury heard," he said. He added that the reasons the trial court gave "do not justify excluding the Waltham murder evidence and it was an abuse of discretion to do so."
"This evidence may have led some jurors to conclude that Tamerlan's influence was so pervasive that Dzhokhar did not deserve to die for any of the actions he took in connection with the bombings, even those taken outside of Tamerlan's presence," Breyer said.
Breyer said, "where death is at stake the courts (and Congress) believe that particular judicial care is required."
Rachael Rollins, the US attorney for the District of Massachusetts who previously said she would try to reinstate the death penalty against Tsarnaev, said Friday that "legal rulings don't erase trauma and pain."
"Our focus today, and always, is on the hundreds of families that were deeply impacted and traumatized by this horrific act of domestic terrorism," she added.
White House press secretary Jen Psaki said Friday that President Joe Biden "clearly supports" Attorney General Merrick Garland's decision to stop federal executions while the Department of Justice reviews the practice.
"The President has expressed before that he has deep concerns about whether capital punishment is consistent with the values that are fundamental to our sense of justice and fairness," Psaki said when asked about the Supreme Court's decision.
She added that Biden has "expressed horror at the events of the Boston Marathon."
"He believes that Tsarnaev should be punished for responsibility in the murder of three innocent people at the marathon for wounding dozens of others and for his role in killing two police officers who are attempting to bring him and his brother to justice."
Psaki said Biden "knows the deep pain that (Tsarnaev's) crime caused."
"He respects the process and the ongoing review that is being led by the Department of Justice and the Attorney General," she added.
This story has been updated with additional details.