( CNN ) -- Boston Marathon bombing suspect Dzhokhar Tsarnaev made a `` statement to his detriment '' during a prison visit by his sister , federal prosecutors said in a court document . The statement was made in the presence of an FBI agent , who was in the room during the visit under special restrictions , according to documents filed in federal court in Boston on Friday . Tsarnaev , in the presence of the agent , `` was unable to temper his remarks and made a statement to his detriment which was overheard by the agent . '' The document did not say what the statement was . The suspect 's alleged statement surfaced during the prosecution 's opposition to a defense motion to do away with restrictions known as Special Administrative Measures , or `` SAMs , '' which include that prison visits be monitored . A defense motion to vacate the measures -- which was unsealed Friday -- describes the SAMs as `` unlawful and unwarranted . '' The measures were imposed in August and restrict Tsarnaev 's access to mail , media , the telephone , and visitors . The defense motion claims the SAMs `` impose extraordinary and severe restrictions impairing the ability of defense counsel to provide competent representation . '' Tsarnaev , 20 , is being held without bail on federal charges in connection with the April 15 bombings that killed three people and wounded more than 250 others . He 's also charged with the killing of an MIT police officer several days later . His trial is set for November 3 . Federal prosecutors said last month they 'll seek the death penalty against Tsarnaev , arguing that he acted in `` an especially heinous , cruel and depraved manner . '' The government argued that the defense motion was not about the restrictions , but about the fact that Tsarnaev allegedly made a detrimental comment in front of an FBI agent , according to the court document . The defense motion `` has nothing to do with the SAMs and everything to do with the fact that Tsarnaev , despite the presence of an FBI agent and an employee of the Federal Public Defender , was unable to temper his remarks and made a statement to his detriment which was overheard by the agent , '' the court document states . The government said the FBI agent was in `` a legally obtained vantage point making his ability to see and hear all which occurred lawful . '' Authorities allege Tsarnaev , a Chechnya-born American , and his brother , Tamerlan , planted two homemade bombs near the finish line of the marathon before allegedly killing a police officer three days later . The attacks triggered the massive manhunt . Police shot and killed the suspect 's brother , Tamerlan Tsarnaev , during the manhunt . Calls to Tsarnaev 's attorneys were not immediately returned Saturday . For victim 's , death penalty decision a 'step forward '
' Tsarnaev is wanted in connection with bombings that killed three people and injured more than 250 others . Prosecutors say he allegedly made a ` ` statement to his family '' during a home visit by his family . His trial is set for October 3 .