Top U.S. security officials are set to face a grilling from law makers who accuse them of failing to investigate the Boston bombing suspects thoroughly enough, after concerns were raised by Russian security sources two years earlier.
Dzhokhar Tsarnaev is now said to be in a fair condition in hospital, one step up from the critical condition he was in before.
In a beside hearing on Monday, he was formally charged with using a weapon of mass destruction resulting in death.
Although his injuries prevent him from speaking he reportedly informed investigators that his older brother Tamerlan – who was killed in a police shootout – was the mastermind of the attack.
He said they acted alone motivated by Islamic radicalisation.
The mother of the suspects, Zubeidat Tsarnaeva, continues to protests their innocence however.
“What happened is a terrible thing,” she said. “But I know that my kids have nothing to do with this.
“I know it. I am (their) mother. You know, I know my kids. I know my kids. Really my kids would never get involved into anything like that,” she added.
Three people were killed and 264 wounded after the brothers allegedly planted pressure cooker bombs near the finish line of the Boston Marathon last Monday.
Ten people lost limbs as the explosives were packed with nails and ball bearings and 48 remained in hospital as of Monday.