FBI: We Couldn't Have Stopped Boston Bombings

Even though a tip put Tamerlan Tsarnaev in the FBI's sights prior to the Boston Marathon bombings, there was essentially nothing the agency could have done to prevent the attack, the bureau has determined. A number of internal reviews zeroed in on how a 2011 request from Russia, which asked that the potential radicalization of Tsarnaev be investigated, was handled; law-enforcement sources tell the New York Times that its conclusion stems from these reviews. The meatiest parts of the Times' piece.

• The law held the FBI back. Based on the kind of investigation they were doing, "federal laws and Justice Department protocols" outlawed the use of surveillance tools like wiretapping, preventing a broader investigation into the bomber, reports the Times.
• What the FBI did do: reviewed Tsarnaev’s criminal, education, and Internet histories; then interviewed his parents; then interviewed him. They uncovered nothing suspicious and ultimately concluded they could not link Tsarnaev to radicals or radical beliefs.
• Even if the FBI had been made aware that Tsarnaev spent time in Russia in 2012 they probably wouldn't have re-opened their investigation, as there was no fresh evidence of radicalization, per the Times.

(More Boston Marathon bombing stories.)