Prosecutors seeking a death penalty conviction of accused Boston Marathon bomber Dzhokhar Tsarnaev on Wednesday said the FBI at the time of his arrest last year believed he and his brother Tamerlan had been trained by a terrorist group because of the sophistication of their weapons and tradecraft.
The Chechen immigrants are alleged to have built the two pressure cooker improvised explosive devices that detonated Monday, April 15, 2013 near the race’s finish line, killing three Bostonians and wounding more than 260 other marathon spectators.
“These relatively sophisticated devices would have been difficult for the Tsarnaevs to fabricate successfully without training or assistance from others,” the U.S. Justice Department said in a filing that opposed defense lawyers’ efforts to have Dzhokar Tsarnaev’s hospital bed confessions tossed out of the case.
Counterterrorism sources have said that investigators have been unable to find any hard evidence of any training or assistance.
But ABC News reported last month that many senior current and former counterterrorism officials — including former Boston Police Commissioner Ed Davis, Homeland Security Committee Chairman Michael McCaul and former Joint IED Defeat Organization director Army Lt. Gen. Michael Barbero — remain skeptical that the Tsarnaevs built their bombs solely from instructions they found posted online.