Lawyers for accused Boston bomber to challenge prison conditions BOSTON (Reuters) - Attorneys for accused Boston Marathon bomber Dzhokhar Tsarnaev are due in court on Tuesday to argue against the restrictive terms of his confinement, which they say are impeding their ability to mount an effective defense. The 20-year-old defendant is being kept separate from other prisoners at the facility west of Boston where he is being held awaiting trial and his lawyers have been ordered not to share messages from Tsarnaev with the outside world. Prison officials and prosecutors argued in court papers that these measures are necessary to protect the safety of both the public and the man accused of the April 15 bombing, which killed three people and injured 264. Prosecutors contend that Tsarnaev and his older brother, Tamerlan, planted two pressure-cooker bombs at the race's finish line, and three days later killed a university police officer in an unsuccessful attempt to steal his gun. That prompted a massive police response, leading to a gunbattle that left Tamerlan dead. Dzhokhar fled and was found hiding in a drydocked boat late on April 19, after a daylong manhunt. Tsarnaev, an ethic Chechen who had lived in Cambridge, Massachusetts, wrote messages on the wall inside the boat including one that, according to court papers, read "Know you are fighting men who look into the barrel of your gun and see heaven, now how can you compete with that." Prosecutors said they believed Tsarnaev, who is not expected to be present in court on Tuesday, would try to inspire other acts of violence if he was treated more leniently in prison. "This was a clarion call to radical militants to follow in his wake," they argued in court papers. The suspect's attorneys, meanwhile, contend that prosecutors mischaracterize the notes, saying that they, "simply state the motive for his actions, a declaration in anticipation of his own death." The American Civil Liberties Union has criticized the Justice Department over Tsarnaev's treatment in prison, saying his isolation threatens his right to a fair trial. But U.S. District Court Judge George O'Toole Jr. said the ACLU would not be permitted to weigh in at Tuesday's hearing. "While there may be no positive rule forbidding it, in my judgment a trial court presiding over a criminal prosecution should not receive or consider volunteered submissions by non-parties except as may be specifically authorized...," O'Toole wrote in his ruling. Tsarnaev has pleaded not guilty to all charges. He could face execution if convicted. Additional reporting by Richard Valdmanis; Editing by Leslie Gevirtz