Boston bombings: Interrogation of Dzhokhar Tsarnaev
The surviving suspect in the Boston Marathon bombings, Dzhokhar Tsarnaev, has been charged with conspiring to use a weapon of mass destruction and could face a death sentence.
As prosecutors build their case, the 19-year-old remains in hospital, reportedly unable to speak because of a gunshot wound to the throat.
How has Dzhokhar Tsarnaev been questioned?
A special team of FBI counter-terrorism agents trained in interrogating "high-value" detainees were sent to Boston's Beth Israel Deaconess Medical Center to interview Dzhokhar Tsarnaev.
Also present were magistrate Judge Marianne Bowler, two US attorney representatives, three public defenders, a court reporter and a doctor, according to a transcript from the hearing.
Mr Tsarnaev responded to questions mostly in writing. He nodded when asked if he was able to answer some questions and whether he understood his rights, the notes read.
He managed to say the word "no" when asked if he could afford a lawyer.
Why was he not advised of his legal rights when he was arrested?
Justice department officials said that in an effort to "gain critical intelligence", they decided to question Mr Tsarnaev "extensively" before giving him the so-called "Miranda" warning of his right to remain silent and to have a lawyer present during questioning.
The magistrate judge present at the bedside arraignment later advised Mr Tsarnaev of his rights and of the charges against him.
The Miranda warning comes from a 1966 Supreme Court ruling that protects suspects from involuntary self-incrimination. If prosecutors want to use at trial statements made by a defendant in custody, law enforcement officials must first have advised them of their rights.
However, justice department officials relied on a 1984 Supreme Court ruling that established an exception allowing prosecutors to use statements made by a defendant prior to the Miranda warning in response to questions from law enforcement officials about an immediate threat to the public, such as a bomb.
A federal judge recently upheld the government's right to use such statements as direct evidence in the case of Umar Farouk Abdulmutallab, a Nigerian man who was sentenced to life in prison for trying to blow up a Detroit-bound flight on 25 December 2009. He confessed to a nurse and spoke freely to FBI agents before being read the Miranda warning.
Has anyone questioned that approach?
Legal rights advocates expressed concern about the use of the "public safety" exception in this case. The executive director of the American Civil Liberties Union said every defendant was entitled to be read Miranda rights.
"The public safety exception should be read narrowly. It applies only when there is a continued threat to public safety and is not an open-ended exception to the Miranda rule," Anthony Romero said in a statement. "We must not waver from our tried-and-true justice system, even in the most difficult of times. Denial of rights is un-American and will only make it harder to obtain fair convictions."
Why is Mr Tsarnaev not being treated as an "enemy combatant"?
The White House said Mr Tsarnaev would not be tried as an enemy combatant in a military tribunal because he was a naturalised US citizen (born in southern Russia).
Several Republican politicians had urged the government to treat Mr Tsarnaev as an enemy combatant, which would give him the same status as those held at Guantanamo Bay. "The accused perpetrators of these acts were not common criminals attempting to profit from a criminal enterprise, but terrorists trying to injure, maim, and kill innocent Americans," senators John McCain, Lindsey Graham and Kelly Ayotte, and congressman Peter King, said in a statement.
But Democratic Senator Carl Levin, chairman of the Senate armed services committee, warned there was "no legal basis for his detention as an enemy combatant".
The Supreme Court has never resolved whether US citizens or foreign nationals arrested on US soil can be detained and tried by the military authorities. During the administration of former President George W Bush, US citizen Jose Padilla was held as an enemy combatant for more than three years. He was transferred to civilian custody in 2005 after his lawyers asked the Supreme Court to consider the issue of his detention. The Obama administration said terrorism suspects arrested inside the US should be handled exclusively by the criminal justice system.
What charges does he face?
Mr Tsarnaev is facing federal charges, including using a weapon of mass destruction and malicious destruction of property resulting in death.
Massachusetts has no death penalty, but because Mr Tsarnaev is being prosecuted under the federal legal system, he could still face execution.
State prosecutors are also expected to bring charges against him, including for the killing of Sean Collier, the Massachusetts Institute of Technology police officer who was allegedly shot by Mr Tsarnaev and his brother on 18 April.
Federal public defender Miriam Conrad, who was at the hospital hearing, confirmed her office would represent Mr Tsarnaev. Ms Conrad has filed a motion asking for two lawyers with experience of death penalty cases to be appointed "given the magnitude of this case", the Associated Press news agency reports.