The motive for the Boston Marathon bombing remains unclear, despite charges being filed against surviving suspect Dzhokhar Tsarnaev.
Federal prosecutors charged him in hospital with using a weapon of mass destruction and malicious destruction of property resulting in death.
He could be sentenced to death if convicted on either count.
At the hearing, he managed to speak once despite a gunshot wound to his throat sustained during his capture.
Mr Tsarnaev, 19, said the word “no” when asked if he could afford a lawyer. Otherwise he nodded in response to Judge Marianne B Bowler’s questions from his bed at Boston’s Beth Israel Deaconess Medical Center.
The next hearing in his case has been scheduled for the end of May.
Meanwhile security officials are expected to face questioning in the Senate Intelligence Committee about whether the FBI mishandled information on Mr Tsarnaev’s 26-year-old brother Tamerlan.
He was interviewed in 2011 at the request of the Russian government based on concerns that he had become a follower of radical Islam. However, it appears no further action was taken.
Tamerlan, who is suspected of carrying out the attack along with his brother, was killed during a manhunt last Friday.
Boston observed a moment of silence for the victims at 14:50 local time (18:50 GMT) on Monday, exactly a week after the attack.
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