BOSTON (AP) — A federal appeals court on Thursday ordered Boston Marathon bomber Dzhokhar Tsarnaev’s case to be returned to a lower court to probe claims of juror bias.

The order from the 1st U.S. Circuit Court of Appeals keeps intact Tsarnaev’s death sentence for now.

But the appeals court said the trial court judge’s investigation into plausible claims of juror bias “fell short of what was constitutionally required.” The appeals court said the judge must now determine whether two jurors should have been stricken because of biases.

“If and only if the district court’s investigation reveals that either juror should have been stricken for cause on account of bias,” Tsarnaev will be entitled to a new trial to determine whether he should be put to death, the court said.

The Boston-based appeals court issued its ruling more than two years after the U.S. Supreme Court reinstated the sentence imposed on 30-year-old Tsarnaev for his role in the bombing that killed three people and injured hundreds near the marathon’s finish line in 2013.

The 1st Circuit took another look at the case after Tsarnaev’s lawyers urged it to examine issues the Supreme Court didn’t consider. Among them was whether the trial judge wrongly forced the trial to be held in Boston and wrongly denied defense challenges to seating two jurors they say lied during questioning.