The lawyers said Tamerlan Tsarnaev had been encouraged by the FBI to observe and report on the Chechen and Muslim community and asked for the release of documents proving their assertion.
“We seek this information based on our belief that these contacts were among the precipitating events for Tamerlan’s actions during the week of April 15, 2013, and thus material to the defense case in mitigation,” the lawyers said in a court filing. "We base this on information from our client’s family and other sources that the FBI made more than one visit to talk with Anzor [his father], Zubeidat [his mother] and Tamerlan, questioned Tamerlan about his Internet searches, and asked him to be an informant, reporting on the Chechen and Muslim community."
“We do not suggest that these contacts are to be blamed and have no evidence to suggest that they were improper, but rather view them as an important part of the story of Tamerlan’s decline. Since Tamerlan is dead, the government is the source of corroboration that these visits did in fact occur and of what was said during them," the filing continued.
Dzhokhar Tsarnaev's lawyers said the elder brother could have interpreted his relationship with the FBI as pressure from the agency and it could have "increased his paranoia and distress" prior to last year's bombing.
The federal government, though, has previously denied it tried to recruit Tamerlan Tsarnaev as an informant.
"Previously, members of the Joint Terrorism Task Force have responded to similar questions relating to whether or not the FBI, Boston Police, Massachusetts State Police or other members of the Joint Terrorism Task Force knew the identities of the bombers before the shootout. Members of the Joint Terrorism Task Force did not know their identities until shortly after Tamerlan Tsarnaev’s death when they fingerprinted his corpse. Nor did the Joint Terrorism Task Force have the Tsarnaevs under surveillance at any time after the Assessment of Tamerlan Tsarnaev was closed in 2011. The Joint Terrorism Task Force was at M.I.T., located in Cambridge, MA, on April 18, 2013, on a matter unrelated to the Tsarnaev brothers. Additionally, the Tsarnaev brothers were never sources for the FBI nor did the FBI attempt to recruit them as sources," a statement from the FBI last year read.