Specific evidence has led federal officials to believe that Tamerlan and Dzhokhar Tsarnaev did not act alone in planning the Boston Marathon attacks, according to arguments submitted Wednesday by the US Attorney’s office.

Dzhokhar Tsarnaev’s lawyers have requested that potentially incriminating comments he made while investigators questioned him at his hospital bedside to be scrapped as evidence in the case against him.

In response to the defense’s motion, the prosecution filed an opposition in the US District Court in Boston to suppress the statement Tsarnaev made during his hospital stay, stating Tsarnaev was never forced to answer any of the questions investigators had asked. The report also states that the prosecution does not plan to use Tsarnaev’s statements as its main argument during the trial and sentencing phase.


One of the filings by the prosecution stated that investigators were led to believe from the bedside questioning that “the Tsarnaevs had accomplices and that they or others might have built additional bombs that posed a continuing danger to public safety.’’

At least eight clues led investigators to this conclusion, including the “sophisticated’’ nature of the bombs that were built that “would have been difficult for the Tsarnaevs to fabricate successfully without training or assistance from others.’’ Also, no traces of crushed black powder from fireworks needed for the devices were found in any location linked to the Tsarnaevs, indicating they may not have built it themselves.

Behavior by the Tsarnaevs, including using temporary phones, and planning another large-scale attack in New York City, also indicated the brothers did not act alone, according to prosecutors.

These details suggest, “others might have radicalized them, directed them, trained them, assisted them, and/or concealed them; and that these others might be planning or poised to carry out additional attacks,’’ the report stated.

Because of this information, the report stated that investigators were justified in immediately questioning Tsarnaev while he was recovering from wounds he sustained during a gunfight with police in Watertown and the hours he spent hiding in a dryrocked boat while the manhunt ensued.


The defense has not responded to these statements.