BOSTON >> Lawyers for Boston Marathon bombing suspect Dzhokhar Tsarnaev asked Friday to delay his trial until at least September 2015.

"We recognize that the government and many members of the public, especially in the Boston area, may want the trial to begin quickly," the lawyers said in a court filing, but it is critically important that both sides have time "to uncover and present all relevant evidence."

Tsarnaev has pleaded not guilty in the April 2013 attack that killed three people and wounded more than 260. He could face the death penalty.

Tsarnaev’s attorneys said his Nov. 3 trial gives them about half the median preparation time allowed other defendants facing a federal death sentence over the past decade.

The lawyers said they need more time to evaluate the "massive amount" of evidence, which they say prosecutors have been slow and disorganized in producing, and to explore mitigating factors that could lessen his sentence if convicted. The attorneys said at a hearing earlier this month they likely could not be ready for a November trial.

Authorities say Tsarnaev and his older brother, Tamerlan, set off the two pressure cooker bombs at the marathon’s finish line. Tamerlan was killed during a shootout with police days later.

Dzhokhar, 21, is a naturalized U.S. citizen who came to the Boston area from Russia with his family more than a decade ago. His lawyers theorize that Tamerlan, who allegedly became radicalized during a visit to his native Chechnya, was the attacks’ instigator.

The lawyers said their investigation faces "barriers of distance, language, and culture," and the fears of witnesses aware of arrests, prosecutions and deportations of some of the Tsarnaevs’ friends. The defense cited an FBI agent’s killing of a friend of Tamerlan during an interrogation in Florida, which authorities have said was self-defense, and the recent convictions of two of Dzhokhar’s friends on obstruction of justice and conspiracy charges.

Separately, the defense responded to prosecutors’ opposition to their change of venue request, saying Tsarnaev’s trial should be moved, or a hearing at least should be held.