Mueller also told the House Judiciary Committee that the government’s recently exposed surveillance techniques, which have been criticized as too sweeping, can be credited with helping spur an investigation of an associate of Tsarnaev, Ibragim Todashev, 27. Todashev was shot to death by an FBI agent in Florida last month during an interview related to his and Tsarnaev’s possible involvement in a Waltham triple homicide. Mueller declined to comment on the specific circumstances during Thursday’s hearing, citing an ongoing investigation.

WASHINGTON — FBI Director Robert S. Mueller III acknowledged on Thursday that a lack of formal communication within the agency may have prevented investigators from alerting Russian authorities that Tamerlan Tsarnaev had returned to Russia before the Marathon bombing, information that Russian officials say could have averted the act of terrorism.


Mueller, who is preparing to step down after 12 years leading the FBI, said that the agency has changed its procedures following the Boston Marathon bombings to require a more formal process of communication between investigators. But he disputed speculation that any communication breakdown facilitated the bombings. “Even if [procedures] had been fixed prior to the Boston bombing, I do not think it would have stopped it,” he said.

Mueller had acknowledged during congressional testimony last month that the agency needed to “scrub and see what we could have done better” in regard to notifications among US intelligence officials about Tsarnaev’s trip in early 2012 to Dagestan, a republic of Russia that is a cauldron of Islamist militancy. But his comments Thursday appear to be the furthest the FBI director has gone in acknowledging the extent of the procedural flaws during the investigation that preceded the bombings.

Tsarnaev, 26, was killed in a shoot-out in Watertown in April. He and his brother, Dzhokhar, 19, who is in custody, are suspected of planting the two bombs that killed three and injured more than 260 on April 15.


Mueller testified Thursday that the FBI did a “thorough job” investigating Tsarnaev when Russian authorities alerted the agency in March 2011 of their belief Tsarnaev was a terrorism threat. But he blamed Russian authorities for failing to respond three times to an FBI request for follow-up evidence after the US-based investigation.

After Mueller testified, an FBI official detailed the new notification procedures, saying that they involve creating a written record in possible terrorism cases so that investigators — in this case the Boston Joint Terrorism Task Force — would formally be alerted to a potential suspect’s whereabouts.

When Tsarnaev traveled to Dagestan, the FBI investigators in Boston who had interviewed him earlier were alerted to his trip only by word of mouth — and nothing was added to his case file about it, said the FBI official, who was not authorized to speak publicly.

“It requires a correction to our procedures, which we have done to assure that every such notice has a recorded record. It cannot be done informally,” Mueller said.

The FBI’s informal communication procedures, at issue soon after the bombing investigation began, drew particular scrutiny in late May when a congressional delegation traveled to meet with Russian intelligence officials and was told that better communication between the FBI and the Russian security agency, known as the FSB, could have prevented the bombing. The FSB was especially concerned that its agents had not been alerted to Tsarnaev’s trip to Dagestan.


Russian authorities believed Tsarnaev “had plans to join the insurgency back in” Dagestan, Representative William R. Keating told the Globe in May, following meetings with Russian authorities. Keating, a Bourne Democrat, was a member of the delegation.

But the FSB did not independently realize he was in Dagestan because he had traveled on documents issued by the country where he grew up, Kyrgyzstan, not Russia or the United States.

Another member of the congressional delegation, Representative Stephen Cohen, a Tennessee Democrat, confronted Mueller with that account during Thursday’s hearing.

“The impression I got, and this is a big leap: They said if they would have known, if you would have followed up and they would have known that he was coming back to Dagestan, that possibly the Boston Marathon bombing would not have occurred,” Cohen said. “I presume that means they would have ‘offed’ him, which would have been great.”

Mueller did not respond directly to the suggestion that Russian agents would have killed Tsarnaev if they had received better intelligence from the FBI. He told Cohen that, “For a variety of reasons, not the least of which the case had been closed some time ago, that particular indication that he was on his on his way back to Russia did not get acted upon.”

Mueller’s other significant disclosure involved Todashev, the Tsarnaev associate killed in Florida. Federal law enforcement officials have been quoted anonymously in various publications as saying that Todashev was confessing to a role in a Waltham triple homicide in 2011 and also implicating Tsarnaev in that crime. The FBI has yet to clarify the circumstances of death of Todashev, who has not been linked to the Marathon bombings.


Mueller shed no new light on that investigation Thursday, saying only “there was a response to a threat,” apparently referring to reports that Todashev threatened an FBI agent during questioning.

But in his comments Thursday he used the case to bolster his argument that government surveillance techniques revealed recently are an important tool for law enforcement. There has been extensive debate over two programs to collect millions of phone, e-mail, and Internet records.

When asked how Todashev came to the agency’s attention, he said it was through “a number of ways including one of the programs that is under scrutiny today.”

Mueller spent much of his three-hour testimony on Thursday defending those programs, facing skepticism from some lawmakers who argued that they are too invasive. At one point, he said that if such programs had existed before the Sept. 11 attacks, those acts of terrorism might have been derailed.

Matt Viser and Bryan Bender of the Globe staff contributed to this report. Noah Bierman can be reached at nbierman@

globe.com. Follow him on Twitter@noahbierman.