Justices Brett Kavanaugh and Elena Kagan clashed in a rare testy exchange between justices on the bench Wednesday as the Supreme Court considered whether an appeals court was justified in overturning Boston Bomber Dzhokhar Tsarnaev’s death sentence.

Tsarnaev was sentenced to death for his role in the 2013 bombings, which he carried out along with his brother Tamerlan, who died while attempting to flee the police shortly after the attack. The district court’s 2015 death sentence was overturned by an appeals court over alleged improper handling of the jury’s media consumption and the court’s exclusion of allegedly mitigating evidence during the sentencing phase.

Justices Sonia Sotomayor and Kagan grilled government lawyer Eric Feigin specifically about mitigating evidence the defense was not allowed to introduce: that Tamerlan may have been involved in a jihad-related triple-murder two years before the Boston Bombing. This evidence was relevant, the defense said, because it bolstered its argument that Dzhokhar would not have committed the bombing if it weren’t for his domineering older brother’s influence.

This file photo released April 19, 2013, by the Federal Bureau of Investigation shows Dzhokhar Tsarnaev, convicted and sentenced to death for carrying out the April 15, 2013, Boston Marathon bombing attack that killed three people and injured more than 260. (FBI via AP, File)

The government and district court argued that the evidence on those murders was not particularly strong. But Kagan asked Feigin to “assume” that the evidence was strong: What should the district court have done then? she asked.

SUPREME COURT CONSIDERS REINSTATING DEATH PENALTY FOR BOSTON BOMBER

“Your entire case rests on the notion that the evidence just wasn’t strong enough,” Kagan said. “How is it the job of the district court to evaluate, much less decide that question?”

But later in the argument Kavanaugh appeared to criticize his colleagues for wanting to assume the evidence that Tamerlan was involved in the triple-murder was strong. The district court’s main reason for leaving that evidence out was that it was weak, Kavanaugh said, so it did not make much sense to approach the case that way.

Justice Elena Kagan clashed with her colleague Justice Brett Kavanaugh Wednesday during oral arguments over Boston Bomber Dzhokhar Tsarnaev’s death sentence.
(Supreme Court of the United States)

Kagan shot back: “The premise was assumed away because that was the role of the jury.”

It was a rare moment of tension on the normally collegial Supreme Court. Even if the justices are taking very different approaches to a case they almost always avoid displays that would appear critical of their colleagues.

Justice Samuel Alito and Chief Justice John Roberts, meanwhile, spent the second half of the Wednesday argument lobbing tough questions at Tsarnaev’s attorney Ginger Anders.

This Oct. 8, 2018, file photo shows Supreme Court Justice Brett Kavanaugh at a ceremonial swearing-in in the East Room of the White House in Washington. Kavanaugh was involved in a testy exchange with Justice Elena Kagan during oral arguments Wednesday. (AP Photo/Susan Walsh, File)

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Roberts asked whether allowing for consideration of the murders would have tipped off an unnecessary “mini-trial” on a question where there is no reliably available answer.

“It isn’t a question of who do you believe — they’re both dead and they’re not there,” Roberts said.

“This was the mitigation case. I don’t think this could have been an improper mini-trial here,” Anders responded, emphasizing that the mitigating evidence of the murders was essentially the defense’s entire case. “It was the trial.”

The case is likely to be decided no later than June of 2022, when the Supreme Court’s current term ends.