Boston bombers are 5th terrorists to survive prior US scrutiny

The FBI is mostly known as top-notch but the Boston Marathon bombing "is the fifth case", including that of Mumbai attack convict David Headley, where potential terrorists have survived the American security scrutiny.
US lawmakers had yesterday grilled top security officials about the handling of the Boston Marathon bombing probe investigation and why one of the Chechen-born suspects flagged as a possible Islamist radical was not tracked more closely.
FBI officials briefed members of Congress behind closed doors here about the investigation into the April 15 blasts that killed three people and injured 264 others.
The Boston Marathon bombing "is the fifth case I'm aware of where a person was brought to the attention of the FBI. ... The FBI examined them and felt they were no threat and they went on to carry out terrorist murders," senior Republican on the House Homeland Security Committee and the House Intelligence Committee, Peter King said.

PolitiFact.Com, run by the Tampa Bay Times, which "fact-checks" statements by public figures said it had checked with King's office, and a spokesman confirmed the four previous examples he was referring were: David Headley, Anwar al-Awlaki, Abdulhakim Muhammed and Nidal Hasan.
Headley, a Pakistani-American born as Daood Gilani, is serving a 35-year sentence for helping organise scouting missions for a 2008 terrorist attack in Mumbai.

In the late 1990s, Headley had served as a confidential informant for the Drug Enforcement Agency and was sent on one mission to Lahore, Pakistan, in which he infiltrated heroin trafficking networks.
But later, his actions raised questions among friends and acquaintances.

"A former girlfriend of Headley's told a bartender named Terry O'Donnell that he wanted to go to Pakistan to fight alongside Islamic militants," ProPublica reported, adding that O'Donnell subsequently contacted an FBI-led task force that was investigating the September 11, 2001, terrorist attacks, PolitiFact.Com said.
On October 4, 2001, "two Defence Department agents working for the task force questioned him in front of his DEA handlers at the drug agency's office," it said.