The Boston Marathon bombing suspects used "relatively sophisticated" bombs with fuses made from Christmas lights and remote-control detonators made from model car parts, federal prosecutors said in a court filing arguing that statements one of them made to FBI agents after being captured shouldn't be thrown out.
The filing yesterday argued against a defence motion to toss suspect Dzhokhar Tsarnaev's statements to the agents because he was questioned without a lawyer.
Prosecutors said 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 a boat where he was captured made it imperative to know if there was a continuing terror threat before informing him of his rights.
Prosecutors also said the brothers used fine black powder from firecrackers as fuel for the bombs and, since none was found in searches of their homes and cars, investigators worried they had help.
"Interviewing Tsarnaev as soon as possible was therefore essential to protect the public from possible harm," prosecutors wrote, citing a public safety exception to the Miranda rule about informing suspects of their rights before interrogation if their statements are to be used in court against them.
The prosecutors said Tsarnaev told agents he and his brother, Tamerlan Tsarnaev, acted alone and there were no more bombs.
Dzhokhar Tsarnaev, 20, has pleaded not guilty to several federal charges. Prosecutors allege he and his brother planted two pressure cooker bombs near the marathon's finish line, killing three people and injuring more than 260 others. His brother was killed during a gunbattle with police on April 19, 2013, four days after the marathon bombing.
Prosecutors said Tsarnaev explained his motive in the note he left in the boat. It said the US government was killing innocent civilians.
"I can't stand to see such evil go unpunished," the note said in part. "We Muslims are one body, you hurt one you hurt us all." It ended, "Stop killing our innocent people and we will stop."
