The final pre-trial hearing in the case was held in Boston ahead of jury selection for a federal trial, which is due to begin on January 5.
Suspect Dzhokhar Tsarnaev, 20, faces the possibility of the death penalty if he is convicted of the April 2013 bombings.
Three people were killed and more than 260 injured when two bombs detonated near the marathon’s finish line.
The Associated Press news agency reports that the courtroom for Thursday’s hearing was packed with FBI agents, police who worked on the case, and survivors and family members.
Dzhokhar Tsarnaev, who was led into the courtroom by US marshals, was wearing a black sweater and grey trousers and sporting a beard, the agency adds.
Prosecutors allege that Dzhokhar Tsarnaev and his older brother, Tamerlan, built and planted the two pressure-cooker bombs.
Dzhokhar and Tamerlan Tsarnaev lived in the Massachusetts town of Cambridge, home of the prestigious Harvard University, after emigrating to the US in 2002 from the Caucasus region of southern Russia.
Officials believe the brothers set off the bombs as an act of retaliation against the US for its military action in Muslim countries.
Tamerlan Tsarnaev was killed during a shootout with police days after the bombing.
Dzhokhar Tsarnaev was wounded and was eventually found by police hiding inside a boat in a residential neighborhood.
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