BOSTON -- Lawyers for Boston Marathon bombing suspect Dzhokhar Tsarnaev say the FBI asked his older brother and fellow suspect to be an informant on the Chechen and Muslim community.
The defense asked a judge Friday to order federal prosecutors to turn over any evidence on brother Tamerlan Tsarnaev, arguing that it could help persuade a jury to spare Dzhokhar Tsarnaev the death penalty if it supports the defense theory Tamerlan was the "main instigator" of the deadly bombing.
Dzhokhar's lawyers say they want records of all FBI contact with Tamerlan based on information from the Tsarnaev family and others that the FBI "questioned Tamerlan about his Internet searches, and asked him to be an informant, reporting on the Chechen and Muslim community."
The defense notes that a report issued earlier this week by the House Homeland Security Committee suggests that government agents monitored Tamerlan and his communications during 2011 and possibly 2012. The report said the FBI Joint Terrorism Task Force conducted a threat assessment of Tamerlan, an ethnic Chechen from southern Russia, in response to a 2011 alert from the Russian government that he was becoming radicalized.
Dzhokhar's lawyers wrote: "Any surveillance, evidence, or interviews showing that Tamerlan's pursuit of jihad predated Dzhokhar's would tend to support the theory that Tamerlan was the main instigator of the tragic events that followed."
A spokesman for the Boston office of the FBI did not immediately return a call seeking comment on the defense claim.
Twin explosions at last April's marathon killed three people and injured more than 260 others. Prosecutors say the Tsarnaev brothers built the pressure cooker bombs and planted them near the marathon's finish line.
Tamerlan Tsarnaev, 26, died several days later during a police shootout. Dzhokhar Tsarnaev, who was 19 at the time of the bombings, is awaiting a November trial on 30 federal counts, including using a weapon of mass destruction. More than half the charges carry the possibility of the death penalty.
In their court filings, Dzhokhar Tsarnaev's lawyers say that if a jury convicts him, its decision on whether to give him life in prison or the death penalty "could well turn on how it apportions the brothers' relative responsibility for conceding and carrying out the attacks, and on the extent to which it views Tamerlan Tsarnaev as having induced or coerced his younger brother to help commit them."
"For this reason," the filings say, "any evidence tending to show that Tamerlan supplied the motivation, planning, and ideology behind the Boston Marathon attack, and that his younger brother acted under his domination is material ... and is also subject to disclosure."
The brothers had lived in the former Soviet republic of Kyrgystan and the Dagestan region of Russia. They moved to Cambridge with their parents and two sisters about a decade before the marathon bombings.