In written testimony submitted before Thursday's hearing by the U.S. House Committee on Homeland Security, Boston Police Commissioner Ed Davis said law enforcement needs to "harden soft targets, especially events that lend themselves toward large gatherings celebratory in nature."
"Images from cameras do not lie. They do not forget," Davis said in his written testimony.
"They can be viewed by a jury as evidence of what occurred. These efforts are not intended to chill or stifle free speech, but rather to protect the integrity and freedom of that speech and to protect the rights of victims and suspects alike."
He warned, however, against, violating civil liberties.
"I do not endorse actions that move Boston and our nation into a police state mentality, with surveillance cameras attached to every light pole in the city," said Davis.
Three people were killed and more than 260 were wounded April 15 when two bombs exploded near the finish line of the Boston Marathon.
Davis said prior to the attack, Boston police were not aware of a Russian intelligence agency tip to the FBI that Tamerlan Tsarnaev, 26, was suspected of engaging in any extremist activity. Tsarnaev was killed in a shootout with police in Worcester, Mass., April 19.
Rep. Michael McCaul, R-Texas, chairman of the committee, criticized the lack of communication between state and federal agencies.
"The idea the feds have this information and it's not shared with state and locals defies why we created the Homeland Security Department in the first place," McCaul said.
"Tamerlan Tsarnaev's trip to the Chechen region, the radical videos proclaiming the caliphate that he posted when he returned and the types of bombs that he and his younger brother used all signal an al-Qaida-inspired terrorist attack."
Former Sen. Joe Lieberman, Ind-Conn., called it a "serious and aggravating omission."
"Nobody bats 1,000 percent, it's true ... but why didn't they involve local law enforcement, who could have stayed on this case?" he asked.
Davis also testified Thursday no one from the University of Massachusetts-Dartmouth came forward to identify Dzhokhar Tsarnaev, 19, after photos of the two suspects were released to the public.
"We need to explain to the community that they have a responsibility to their community and to their nation and to what's right to report the kind of activity that these brothers were involved in prior to the incident," Davis said. "And I think that's the first line of defense."
Lieberman said it wouldn't have been easy, but the Boston attack, the first successful terrorist attack, on civilians in the United States since Sept. 11, 2001, could have been stopped.
"In a literal sense, the homeland security system, we must acknowledge that we built after 9/11 to protect the American people from terrorist attacks failed to stop the Tsarnaev brothers," he said.
Lieberman said the April 15 attack "should again teach us that the enemy we face is violent Islamist extremism, not just al-Qaida. Osama bin Laden is dead, and the remaining leadership of al-Qaida is on the run, but the ideology of violent Islamist extremism is rapidly spreading."
He said Muslim leaders and members of the world's Muslim communities, "including our own fellow Americans who are Muslim, probably have the greatest capacity to do the most important work of counter-radicalization, but the rest of us have a responsibility to help."