By MATTHEW CHAYES. AND KEVIN DEUTSCH
The flow of information that Dzhokhar Tsarnaev was providing to FBI investigators abruptly stopped when a federal magistrate judge showed up at the hospital unannounced and read him his Miranda rights, a source said Thursday.
It's possible valuable intelligence was not obtained because Tsarnaev, the surviving suspected Boston Marathon bomber, has not spoken to interrogators since Monday's bedside hearing, the source said.
The investigators, who specialize in grilling terrorists, were 16 hours into the interrogation of Tsarnaev, 19, when U.S. Magistrate Judge Marianne B. Bowler showed up with a federal prosecutor and public defender, Rep. Peter King said Thursday.
The source said the FBI was caught off guard because the investigators believed they had 36 to 48 hours to question Tsarnaev under the pre-Miranda public safety exemption.
The FBI's website notes that the exemption "permits law enforcement to engage in a limited and focused unwarned interrogation and allows the government to introduce the statement as direct evidence."
King (R-Seaford) said the investigators "were forced to stop by the judge."
In a statement Thursday afternoon, the acting clerk of court, Robert Farrell, said: "The court has no comment on this issue."
A source directly familiar with the magistrate's thinking, who spoke anonymously because the source wasn't authorized to comment publicly, said that the magistrate processed Tsarnaev because "as soon as someone is charged, they're supposed to be seen without unnecessary delay."
"We see people without undue delay whether it's a felony in possession of a firearm" or an accused terrorist, the source said.
"Some congressman from New York doesn't know how the court system works," the source said. "Once you're charged, you have a right to be seen," the source said, noting the complaint was signed Sunday night.
King, chairman of the Homeland Security Subcommittee on Counterintelligence and Terrorism, called for a "full investigation" of the matter.
"This was such a productive interrogation, and so much information was coming out," King said, adding that the investigation could "go a lot wider than it is right now."
The congressman cited the possibility of finding out more about undiscovered explosives, co-conspirators and links to outside terrorist groups.
"It was cut off before they could get to all of that," King said.
A second source familiar with the investigation said the FBI investigators in the hospital "were not happy, I can tell you that."
According to a transcript of Monday's proceeding at Beth Israel Deaconess Medical Center in Boston, Bowler advised Tsarnaev of his "right under the Constitution to remain silent. Any statement made by you may be used against you in court, and you have the right now to have your own words used against you."
Bowler also advised Tsarnaev of the charges against him -- use of a weapon of mass destruction and malicious destruction of property resulting in death -- and that he faced the maximum penalty of life in prison or death.
Tsarnaev and his brother Tamerlan Tsarnaev, 26, who died Friday in a shootout with police, are accused of setting off the April 15 explosions that killed three people and injured more than 260 near the marathon's finish line.