Attorneys for Tsarnaev, 26, maintain he was under the sway of his violent, domineering older brother Tamerlan when he went along with his plan to attack the race, and that the trial judge wrongfully barred the defense from telling jurors about Tamerlan Tsarnaev’s suspected involvement in the earlier Waltham killings.

That triple slaying is key to Tsarnaev’s pending appeal of his death sentence for his admitted role in the April 2013 bombings, which killed three people, including an 8-year-old Dorchester boy, and wounded more than 260 others.

Lawyers for Boston Marathon bomber Dzhokhar Tsarnaev scored a victory Wednesday when a federal judge granted their request to partially unseal a search warrant that allegedly linked his deceased older brother to a Waltham triple murder in 2011.


Tsarnaev’s lawyers have said in court papers that partially unsealing the warrant would help them “effectively and publicly address his claim that the exclusion of evidence of Tamerlan Tsarnaev’s involvement in the Waltham triple homicide violated” Dzhokhar Tsarnaev’s due process rights during his 2015 trial.

The brothers carried out the Marathon bombings on April 15, 2013, and Tamerlan Tsarnaev was killed days later in a confrontation with police in Watertown. Dzhokhar Tsarnaev was captured and ultimately sentenced to death following his 2015 conviction.

The search warrant in question was for Tamerlan Tsarnaev’s Honda CR-V. Law enforcement officials were looking for possible “forensic evidence” in the vehicle linking Tamerlan to the 2011 Waltham slayings, Dzhokhar Tsarnaev’s attorneys have said in court papers.

An appellate court last week denied the request from Tsarnaev’s legal team to partially unseal the warrant but said they could re-file the motion in the lower US District Court, where he initially stood trial.

On Wednesday, Judge George A. O’Toole Jr., who presided over the 2015 trial, granted the request, which prosecutors did not oppose. O’Toole’s order said the clerk “shall docket publicly a copy of the redacted second search warrant as proposed by the defendant.”


In court papers filed in June, prosecutors insisted that O’Toole properly shielded jurors from hearing information about the Waltham case.

“The district court correctly concluded that evidence of the Waltham murders, which arose out of a drug-related robbery and were completely unrelated to the marathon bombing, was not relevant mitigating evidence,” prosecutors wrote. “Contrary to [Dzhokhar] Tsarnaev’s claim, the Waltham evidence did not show that Tamerlan ‘influenced’ or ‘intimidated’ him into committing the crimes in this case or that [Dzhokhar] Tsarnaev played a lesser role in the bombing.”

The US Court of Appeals for the First Circuit is scheduled to hear oral arguments in Tsarnaev’s appeal in December. He’s currently incarcerated at a federal supermax prison in Colorado.

Travis Andersen can be reached at travis.andersen@globe.com. Follow him on Twitter @TAGlobe.