The lawyers said that Mr. Phillipos, 19, had nothing to do with the bombings and was frightened and confused when he was interrogated about going with two other friends to the college dorm room of Dzhokhar Tsarnaev, one of the two chief suspects in the case, and removing a backpack and fireworks that the investigators consider to be evidence. The other suspect, Mr. Tsarnaev’s older brother, Tamerlan, 26, died after a shootout with the police.
As Washington gears up this week for its first hearings on the Boston Marathon bombings, Representative Peter T. King, Republican of New York, said Sunday that he believed the brothers did not act alone.
“It’s very difficult to believe that these two could have carried out this level of attack with this level of sophistication and precision acting by themselves, either without training from overseas or having at least facilitators here at home,” Mr. King, a former chairman of the House Committee on Homeland Security, said on the CNN program “State of the Union.”
Noting that there were multiple bombs involved, he added, “No, I think there had to be assistance, and that’s why the F.B.I., I think, is going after this so vigorously and effectively.”
So far, only Dzhokhar Tsarnaev, 19, has been charged with carrying out the bombings, which killed three people and wounded more than 260 others on April 15 near the finish line of the prestigious Boston race. His brother, Tamerlan, died after the brothers tried to elude the authorities; according to his death certificate, he was killed by gunshot wounds and blunt trauma after being hit by an S.U.V. driven by Dzhokhar as he fled.
The F.B.I. on Sunday conducted another search of Tamerlan Tsarnaev’s apartment in Cambridge. A senior law enforcement official, who asked not to be identified, said that it was a routine follow-up search, but did not elaborate on what, if anything, the F.B.I. found.
Gordon Lindley, who lives across the street from the building, said he saw what appeared to be law enforcement officials, including two to three men wearing F.B.I. jackets, carry at least a dozen boxes to a large truck.
Also on Sunday, an uncle of the Tsarnaev brothers arrived with three friends at a funeral home in Worcester, Mass., to prepare Tamerlan’s body for burial, although the question was where.
“I’m dealing with logistics,” said the uncle, Ruslan Tsarni, a businessman from Maryland who said he had not seen either of the Tsarnaev brothers in about five years. “A dead person needs to be buried — that’s what tradition requires, that’s what religion requires, that’s what morals require.”
Peter Stefan, the owner of the Graham Putnam & Mahoney Funeral Parlors, has been criticized for accepting the body. On Sunday, a small group of protesters gathered with American flags and signs with phrases like “Bury this terrorist on US soil and we will unbury him.”
Mr. Stefan has been unable to find a cemetery willing to accept the body and said he planned to call cemeteries with areas reserved for Muslims, as well as the city of Cambridge, Mass., where Mr. Tsarnaev lived.
But the Cambridge city manager, Robert W. Healy, pre-emptively issued a statement on Sunday urging Mr. Stefan and the family not to make such a request. “I have determined that it is not in the best interest of ‘peace within the city’ to execute a cemetery deed for a plot within the Cambridge Cemetery for the body of Tamerlan Tsarnaev,” said Mr. Healy, who said that federal officials should handle it.
Mr. Tsarni emerged wearily from the funeral home’s work room after spending hours washing and wrapping his nephew’s body with three of his friends.
“We did what we have to do, something no one else could have done,” he said. “Now all we need is a little luck.”
Mr. Tsarni said he had had little contact with Mr. Tsarnaev’s immediate family, although he had spoken to the brothers’ father. “He’s not really in a reasonable state of mind,” Mr. Tsarni said. He had not spoken to Katherine Russell, 24, Tamerlan’s widow. “I wanted to,” Mr. Tsarni said. “She’s been the closest person to him.” The uncle said he planned to visit Dzhokhar Tsarnaev, who is in a medical prison center at Fort Devens, Mass. “This is another person left all to himself,” Mr. Tsarni said.
Mr. Phillipos is to appear in Federal District Court in Boston on Monday and will ask to be released on bond, his lawyers said. In a criminal complaint filed last week, federal investigators said that Mr. Phillipos had given three versions of events on the night of April 18 — the day that the F.B.I. released photographs of two men identified as suspects — until he admitted that he and two other friends had gone to Mr. Tsarnaev’s dorm room on the campus of the University of Massachusetts Dartmouth.
The other two friends — Azamat Tazhayakov and Dias Kadyrbayev, originally from Kazakhstan — have been charged with obstruction of justice and destroying evidence, and each face a five-year prison sentence and $250,000 in fines. They are to appear in court next week. Mr. Phillipos, an American, faces a stiffer sentence: eight years in prison and $250,000 in fines.
Mr. Phillipos’s lawyers, Derege B. Demissie and Susan B. Church, said in the court papers that the charges against their client were “refutable.”
They said that he was no longer enrolled at the college and had not seen Mr. Tsarnaev or the others for two months. Then, by “sheer coincidence and bad luck,” he happened to be on campus for a seminar on April 18.
Mr. Phillipos, who attended high school with Dzhokhar Tsarnaev, was questioned a number of times without a lawyer present, his lawyers wrote.
“This case is about a frightened and confused 19-year-old who was subjected to intense questioning and interrogation, without the benefit of counsel and in the context of one of the worst attacks against the nation,” the lawyers wrote. “The weight of the federal government under such circumstances can have a devastatingly crushing effect on the ability of an adolescent to withstand the enormous pressure and respond rationally.”
In an attempt to show that Mr. Phillipos is not a flight risk, his lawyers said he “comes from a well-educated family and was raised by a hard-working single mother” as she pursued three college degrees, including a bachelor’s degree in political science from Northeastern University and a master’s degree in social work from Boston University.
His mother, Genet Bekele, is a social worker who emigrated from Ethiopia, lives in Cambridge and specializes in handling domestic violence cases. She filed one of several affidavits attesting to her son’s character, saying she had raised him “with Christian values and taught him the value of working hard.”
“My whole family is in complete shock over the accusation made against him,” she said.