Lawyers for Boston Marathon bombing suspect Dzhokhar Tsarnaev urged a judge Wednesday to order federal prosecutors to turn over any evidence they have about his brother’s participation in a 2011 triple killing or to consider postponing Tsarnaev’s trial.

Tsarnaev, who has pleaded not guilty in the 2013 bombing, faces the possibility of the death penalty if convicted. Three people were killed and more than 260 injured in the explosions.

Authorities say Tsarnaev, then 19, and his 26-year-old brother, Tamerlan, detonated pressure-cooker bombs near the marathon finish line. Tamerlan Tsarnaev was killed several days later in a shootout with police.

During a status conference Wednesday in federal court, Tsarnaev’s lawyers said prosecutors have not turned over any evidence about Tamerlan Tsarnaev’s supposed role in the triple slaying since last year, when they said in court papers that Tamerlan Tsarnaev’s friend told investigators of the older brother’s participation.

That friend, Ibragim Todashev, was shot and killed at his Florida home while being questioned by the FBI and Massachusetts State Police. Authorities have said an FBI agent shot Todashev after he charged at a state trooper with a pole, but Todahsev’s family has challenged that account.

Dzhokhar Tsarnaev’s lawyer William Fick told Judge George O’Toole Jr. that any evidence of Tamerlan’s involvement in the triple slaying would be “extremely relevant,” because it could bolster a defense argument that the younger brother was influenced or coerced by his older brother to participate in the bombings.

“I really can’t overstate the potential importance of this information,” Fick said.

Assistant U.S. Attorney William Weinreb said federal prosecutors have no additional information to give the defense. He said Middlesex County prosecutors are investigating the triple homicide in Waltham, a Boston suburb.

“What they have in their files is in their files. It’s not in our possession,” Weinreb said.

The judge did not immediately rule on the defense request and did not indicate when he would issue his ruling.

Tsarnaev’s lawyers also requested a hearing on media leaks they say could jeopardize the 21-year-old’s right to a fair trial.

In a court filing last month, Tsarnaev’s lawyers cited a Newsweek magazine article containing statements from unnamed law enforcement sources. The defense, which has complained twice before about media leaks, wants the judge to hold a hearing to question supervising law enforcement officers to testify about their efforts to stop unauthorized communications.

Weinreb said prosecutors have sent a letter to all law enforcement agencies involved in the marathon investigation telling them not to talk to the press.

O’Toole did not immediately rule on the defense request for a hearing.

Jury selection in Tsarnaev’s trial is scheduled to begin Jan. 5.

O’Toole said that about 1,200 potential jurors will be asked to fill our questionnaires. That pool will be whittled down to a smaller number of people who will be questioned individually. A panel of 12 jurors and six alternates would then be chosen to hear the case.

The defense argued that they are not required to turn over their witness list before Tsarnaev’s trial.

Attorney Judy Clarke said the defense has already been struggling to get witnesses to talk and is concerned that turning their names over to the government might lead to them to refuse to testify.

O’Toole ordered the defense to give its witness list to prosecutors by Dec. 29.

Tsarnaev, who has not appeared in court since his July 2013 arraignment, will be in court for the final pretrial hearing on Dec. 18.

(AP)