(NECN: Justin Michaels) - In a court filing Wednesday, federal prosecutors say the Boston Marathon bombing suspects used "relatively sophisticated" bombs in their attack at the finish line.
The devices included fuses made from Christmas lights and remote-control detonators made from model car parts.
In the court filing, prosecutors argued against a defense motion to throw out surviving suspect Dzhokhar Tsarnaev's statements to FBI agents he made without a lawyer present.
Also in Wednesday's court filing, Prosecutors say the bombs, comments Tsarnaev and his brother made to a carjacking victim that they might explode more bombs in New York, and a note Tsarnaev wrote in the Watertown boat where he was captured made it imperative to know if there was a continuing terror threat before informing Tsarnaev of his rights.
Tsarnaev's attorneys wanted information gained during that 36 hour interview before his rights were read to be thrown out.
Prosecutors also say the brothers used fine black powder from firecrackers as fuel for the bombs and, since none was found in their homes and cars, investigators worried they had help.
The prosecutors said Tsarnaev told agents he and his brother, Tamerlan Tsarnaev, acted alone and there were no more bombs.
Tsarnaev has pleaded not guilty to federal charges that he and his deceased brother Tamerlan planted two pressure cooker bombs near the Boston Marathon finish line last April, killing three people and injuring more than 260 others. Tamerlan Tsarnaev was killed during a gun fight with police in Watertown four days after the attack.
In other filings by the prosecution they reject defense motions that the federal death penalty should be declared unconstitutional.
The trial is set to begin in November.