Tamerlan Tsarnaev

Tamerlan Tsarnaev featured in evidence about the charged events and in the defense's account of the brothers' relative responsibility. Judy Clarke's opening acknowledged Dzhokhar's involvement but argued that Tamerlan planned and led the acts and drew his younger brother into them. Surveillance presentations traced Tamerlan's movements along Boylston Street, while phone evidence documented calls between the brothers around the explosions. Cross-examination distinguished general cell-site locations from precise positions and network-use durations from actual conversation lengths. Joseph Reynolds testified that Tamerlan exited the Mercedes and fired at his cruiser in Watertown. Reynolds also described officers restraining Tamerlan before the Mercedes, which he identified Dzhokhar as driving, struck him.

Defense testimony also addressed Tamerlan's beliefs and conduct. Mark Spencer compared computer evidence associated with the brothers and described Skype material linked to Tamerlan. Loay Assaf recalled Tamerlan interrupting mosque sermons. Amanda Ransom described witnessing a street assault and feeling threatened during a later apartment incident, while distinguishing her observations from Katherine Russell's accounts. Ransom also reported a subsequent message from Katherine denying that Tamerlan had threatened her; her testimony concerned his personal conduct rather than his influence over Dzhokhar in the charged acts. Counsel disputed proposed penalty-phase evidence alleging Tamerlan's involvement in the Waltham murders. The government challenged reliability and warned of a collateral inquiry, while the defense argued that the allegations supported its influence theory. The court asked about corroboration, and the argument ended without a recorded ruling. In the mitigation findings, three jurors found the older-brother influence and planning-and-leadership factors; five found that Tamerlan became radicalized first and encouraged Dzhokhar to follow.