Prosecutors say the sophistry of the explosives gave investigators reason to believe that the suspects may have had accomplices, prompting them to question Dzhokhar Tsarnaev while he was being treated in the hospital.
The suspected Boston Marathon bombers used parts from Christmas lights and model cars to construct the sophisticated explosives used in the attack, federal prosecutors said in a Wednesday court filing.
Federal prosecutors are seeking the death penalty for Dzhokhar Tsarnaev, one of the two suspects in the April 16, 2013 bombings that killed three people and injured 264 others. His brother and alleged accomplice, Tamerlan, died during a police shootout following the search for suspects.
Prosecutors said in the filing the sophisticated nature of the explosives gave reason to believe that the brothers received assistance, the Boston Globe reports.
“In short, the facts and circumstances known to law enforcement at the time they interviewed Tsarnaev provided ample reason to believe that the Tsarnaevs did not act alone,” the prosecutors said in the filing, according to the Globe.
Prosecutors also said the brothers appeared to have crushed and emptied fireworks containing black powder for the bombs, but investigators did not find significant traces of the powder at the brothers’ residences or cars.
The filing also argues the court should not suppress statements Dzhokhar Tsarnaev made to FBI agents while being treated in a hospital after his arrest because investigators had to determine if the suspect had accomplices who could have posed a threat. Tsarnaev’s defense has argued that the interrogations are inadmissible because he was interrogated without access to a lawyer.