Tsarnaev 'Knew Brother Took Part in Triple Murder' Defense pushing for info on 2011 slayings By Rob Quinn, Newser Staff Posted Oct 13, 2014 2:00 AM CDT 21 comments Comments This combination of photos shows brothers Tamerlan, left, and Dzhokhar Tsarnaev, suspects in the Boston Marathon bombings on April 15, 2013. (AP Photos/Lowell Sun and FBI, File) (Newser) – Tamerlan Tsarnaev's involvement in a grisly 2011 triple murder is relevant to his brother Dzhokhar's trial if Dzhokhar knew about it, defense lawyers say—and a federal prosecution witness is prepared to testify that he did. Court filings released Friday reveal that the surviving Boston Marathon bombing suspect's lawyers are pushing for government information on the slayings, which could help what appears to be a defense strategy of arguing that Tamerlan dominated his younger brother and bullied him into taking part in the attacks, Yahoo News reports. The 2011 murders are still officially unsolved, and a friend who allegedly admitted taking part in the killings with Tsarnaev was shot dead by an FBI agent during questioning last year. Tsarnaev's lawyers say "even the government has conceded" that the murders could be relevant to the trial, which begins in January, the AP reports. "Simply put, information and evidence tending to show that Tamerlan Tsarnaev participated in a triple homicide in 2011, and information depicting the brutality of those murders, is critical to the defense case in mitigation," lawyers said in their filing. "Such evidence would tend to corroborate Tamerlan's dominant role in the charged offenses and would place the brothers' respective personal characteristics and relative culpability into stark relief." Prosecutors are seeking the death penalty for Tsarnaev, who has pleaded not guilty.