A US jury on Friday sentenced 21-year-old Dzhokhar Tsarnaev to death for his role in the 2013 Boston Marathon bombings, one of the worst assaults on American soil since the September 11, 2001 attacks.

It took the jury more than 14 hours to choose death on six of 17 capital counts for the Muslim former university student of Chechen descent who came to the United States as a child and became a citizen.

Their only other option was life without the possibility of release in America's toughest "super-max" prison in Colorado, which some have dubbed the "Alcatraz of the Rockies."

The same 12-member panel of jurors convicted him on April 8 on all 30 counts relating to the April 15, 2013 bombings, the murder of a police officer, a carjacking and a shootout while on the run.

Three people were killed and 264 others wounded, including 17 who lost limbs, in the twin blasts near the finish line at the northeastern city's popular marathon.

Tsarnaev went on the run and was arrested four days later, hiding and injured in a grounded boat on which he had scrawled a bloody message defending the attacks as a means to avenge US wars in Iraq and Afghanistan.

He showed no emotion as he stood, flanked by female lawyers and wearing a dark blazer with his hands clasped before him as the court clerk declared the death penalty verdict before a hushed room.

US Attorney General Loretta Lynch called the sentence a "fitting punishment."

- Death penalty opposition -

The verdict in the federal case came despite widespread local opposition to capital punishment in Massachusetts, a largely Democratic state that abolished the death penalty in 1947.

Prominent survivors, including the parents of the youngest victim Martin Richard, had also opposed the death penalty on the grounds that years of prospective appeals would dredge up their agony.

The Richard parents were among other victims and survivors who crammed into the courtroom on Friday to hear the verdict.

The jury's 24-page verdict form showed that few on the panel bought into the defense argument that Tsarnaev was influenced by his 26-year-old brother Tamerlan, who was shot dead by police on the run.

Only three said he acted under Tamerlan's influence and that Tamerlan planned, led and directed the bombings. Only two determined that Tamerlan shot dead a university police officer while the pair were on the run.

Only one juror determined that he was unlikely to commit or incite acts of violence in the future while serving a life sentence.

The six death counts all relate to the pressure cooker bomber planted by Tsarnaev at the marathon finish line. His brother planted the other.

Judge George O'Toole will now formally sentence Tsarnaev at a hearing expected to be held later in the year.

Government prosecutors delivered a powerful closing statement Wednesday, calling Tsarnaev a remorseless terrorist who deserves to die and declaring that life imprisonment would be the "minimum" punishment.

They said he lived a double life as a pot-smoker enrolled at University of Massachusetts, Dartmouth and self-radicalized as early as high school, captivated by the teachings of US-Yemen cleric Anwar al-Awlaki.

Key was his note justifying the attacks.

"No remorse, no apology. Those are the words of a terrorist convinced he has done the right thing," US assistant attorney Steven Mellin said.

- Tough trial, grim testimony -

Since the federal death penalty was reinstated in 1988, only 79 people have been sentenced to die and only three have been executed, says the Death Penalty Information Center.

Three other death verdicts were turned into life sentences after new trials were granted.

The decision caps a harrowing, more than two-month trial that saw the court relive the horror of the attacks day after day through grisly videos and heartbreaking testimony from those who lost limbs and loved ones.

The attacks shocked the relatively small northeastern city of Boston and revived fears of terrorism in the United States after the September 11, 2001 strikes on New York, Washington and Pennsylvania.

The death verdict is a tough defeat for lead defense attorney Judy Clarke, who has saved some of America's most notorious criminals and convicted terrorists from capital punishment.

She admitted Tsarnaev's guilt from the outset but said he was manipulated into taking part by his more radical elder brother.

Her team deployed dozens of witnesses during a three-week sentencing phase in an attempt to save him from the death penalty.

Tsarnaev "would never have done this but for Tamerlan. The tragedy would never have occurred but for Tamerlan," she said.

She appealed to the jury to consider Tsarnaev's young age, his brother's domineering influence, his parents' return to Russia in 2012, the affection of his friends and teachers, and his apparent remorse.

Clarke portrayed an impressionable youth who was fed Al-Qaeda magazines and lectures by Tamerlan, the true mastermind of the attacks, the ignored younger son of a mentally ill father and an "intimidating," radicalized mother.

Since then, she said, Tsarnaev had expressed genuine remorse during prison visits by a Roman Catholic nun. The jury determined that Tsarnaev had demonstrated a lack of remorse.
Source: AFP