Accused bomber Dzhokhar Tsarnaev should be put to death if he is found guilty of planting bombs that killed three people and wounded 264 at the Boston Marathon last year, the US government's chief prosecutor says.
US Attorney General Eric Holder said in a statement that he was authorising trial prosecutors to seek the death penalty against Tsarnaev, who is charged with committing one of the largest attacks on US soil since September 11, 2001.
"The nature of the conduct at issue and the resultant harm compel this decision," Holder said. Holder had faced a Friday deadline for deciding whether to seek the death penalty as part of Tsarnaev's upcoming trial in Boston.
The decision drew fire from the American Civil Liberties Union of Massachusetts, which pointed out the case would be prosecuted in a state that had scrapped the death penalty decades ago.
"I wish Federal officials would have respected the clear wishes of the people of Massachusetts, who were on the front lines in this tragic event," Carol Rose, the executive director of the ACLU of Massachusetts said.
A Boston Globe survey found last year that 57 per cent of Boston residents favored life in prison for Tsarnaev, if he is convicted, with 33 per cent in favour of execution.
Prosecutors say that Tsarnaev, 20, and his 26-year-old brother Tamerlan planted a pair of homemade pressure-cooker bombs at the race's crowded finish line on April 15, 2013, killing three people - including an 8-year-old boy. The blast also wounded 264 others, many of whom lost limbs.
Three nights later, the pair killed a university police officer and later engaged in a shootout with police that left Tamerlan dead, prosecutors say.
Austin Sarat, Professor of Jurisprudence and Political Science at Amherst College in Massachusetts, said the nature of the case probably left the Justice Department little choice but to seek capital prosecution.
"If the harm is unusual, if the harm is dramatic, gruesome, and devastating, it is often very hard for any other factor to outweigh it," he said. "I'm not surprised by this decision."
The younger Tsarnaev pleaded not guilty to the criminal charges. Justice Department officials said the nearly seven months since the attack was necessary to evaluate fully the circumstances of the case and to gather recommendations from prosecutors advising Holder.
Holder has said he is not a proponent of the death penalty because he believes its value as a deterrent is questionable, but since becoming attorney general in 2009, he has authorised prosecutors to seek the death penalty in 36 cases, according to the Justice Department.
Attorneys for Tsarnaev have argued against a possible death sentence, in part because they claim Dzhokhar was following the lead of his older brother.
They have also accused the government of throwing up unfair obstacles to hinder preparation of their client's defence, including seeking to rush the start of trial and not sharing important evidence.
Tsarnaev's defence attorney Miriam Conrad declined to comment on Holder's decision on Thursday.
The blasts killed 8-year-old Martin Richard as well as Krystle Campbell, 29, and Chinese national Lu Lingzi, 23. Tsarnaev is also accused in the shooting death of Sean Collier, 27, the university police officer.
A spokesman for Richard's family said the family did not want to comment. Efforts to reach the families of the other victims were not immediately successful.
A trial date for Tsarnaev has not yet been set.