Could a more vigilant public have prevented the Boston Marathon bombing?

Joe Lieberman testified in Congress that better coordination between federal and local law enforcement or a tip to police from someone who knew of Tamerlan Tsarnaev's views could have prevented the bombing.

Former US Sen. Joe Lieberman argued Tuesday that the Boston Marathon terrorist attack could have been prevented by greater public vigilance on the part of citizens acquainted with the alleged bombers.

He said better coordination between federal and local law enforcement also might have enabled authorities to head off the deadly attack.

“In this case there were people who clearly could have prevented the massacre at the marathon by just saying something,” Mr. Lieberman, the former chairman of the Senate Committee on Homeland Security and Government Affairs, told the House Homeland Security Committee.

He pointed to the friends, family, and acquaintances of Tamerlan and Dzhokhar Tsarnaev, the brothers who allegedly planted the bombs and were later responsible for the shooting death of a police officer.

“Leaders and members of the Boston mosque that threw Tamerlan out because of his extreme views could have said something to the police and even done something to counter his radicalization,” the former independent Senator from Connecticut told the hearing.

Lieberman acknowledged that preventing the attack wouldn’t have been easy, but he asserted that it might have been possible.

His statements amounted to a passionate call for Americans to engage more fully with the “if you see something, say something” slogan that citizens see in places like subway stations.

And, amid efforts to identify any security failures and learn lessons from the bombing, his remarks put the focus on local action, not just questions of intelligence sifting at the federal level.

Boston Police chief Ed Davis, who also testified at the Thursday hearing, echoed some of Lieberman’s concerns but was cautious in comments about whether the terrorist actions could have been prevented.

“We certainly need to enlist the community better,” Commissioner Davis said. “There’s no computer that’s going to spit out a terrorist’s name. It’s the community being involved in the conversation and being appropriately open to communicating with law enforcement when something awry is identified.”

That cooperation, more than technology or bomb-sniffing dogs, “should be our first step,” he said.

Rep. Mike McCaul (R) of Texas, who chairs the Homeland Security Committee, asked Davis whether his department had received word from federal officials about Tamerlan Tsarnaev visiting Dagestan in 2012, viewing jihadist websites, or being on a watch list of potential terror risks.

Davis said neither Tsarnaev brother had come to his department’s attention prior to the bombings.

“We would have taken a hard look at these individuals,” he said, if such information had arrived. But he said it’s unclear if "we would have done anything differently."

He noted that the FBI, after receiving a query from Russian authorities, interviewed Tamerlan Tsarnaev but saw nothing suspicious.

Lieberman called the federal failure to share information about Tamerlan Tsarnaev with local police a “serious and aggravating omission.”

Representative McCaul called it a lapse that “defies why we created the Department of Homeland Security in the first place."

Erroll Southers, a homeland security expert who appeared at the hearing, said Americans must balance vigilance with mutual trust and respect for the rule of law. “Singling out a person or entire community as suspect based on anything other than fact undermines the community cohesion we need to counter the persistent threat,” he said in his prepared testimony.