A US jury began deliberations Wednesday on whether to sentence convicted Boston bomber Dzhokhar Tsarnaev to death or life in prison for carrying out one of the bloodiest attacks in America since 9/11.

The jury heard closing statements from prosecutors that portrayed Tsarnaev as a remorseless militant who deserves to die, and from the defense that he was a "lost kid" manipulated by his radicalized older brother.

They were given lengthy instructions by federal Judge George O'Toole and given less than an hour to deliberate before being dismissed for the day and instructed to return Thursday.

The same jury found the 21-year-old former student guilty last month of carrying out the April 15, 2013 bombings that killed three people and wounded 264 at the finish line of the northeastern city's popular marathon.

The Muslim immigrant, who arrived in the United States with his parents at aged eight and took US citizenship a year before the attacks, was convicted on all 30 counts related to the bombings, and the subsequent murder of a police officer, a carjacking and a shootout while on the run.

His older brother Tamerlan, 26, was shot dead by police, leaving Dzhokhar to stand trial alone after he was captured.

Seventeen of his convictions carry the death penalty, the imposition of which on any single count must be unanimous.

Assistant US attorney Steve Mellin told jurors that Tsarnaev, who sat motionless staring at the table in front of him dressed in a dark blazer, deserved to die for inflicting carnage and terror on society.

"The only sentence that will serve justice in this case is the sentence of death," Mellin said.

The two brothers were equal partners in crime, he said, and Tsarnaev justified the attacks to avenge America's wars in Iraq and Afghanistan, penned in a bloody note before he was captured in a parked boat.

"No remorse, no apology. Those are the words of a terrorist convinced he has done the right thing. He felt justified in killing, maiming and seriously injuring innocent men, women and children," he said.

- Jail would be 'minimum' sentence -

The prosecutor recalled harrowing testimony from the loved ones of the dead, including the parents of the youngest victim eight-year-old Martin Richard and stressed the "excruciating" injuries endured by survivors.

Aggravating factors, which jurors will have to determine to award the death penalty, far outweigh 21 mitigating factors advanced by the defense in a bid to secure him life without parole, the prosecutor said.

Prosecutors rubbished any suggestion that America's most maximum security jail, ADX Florence in Colorado, would be a worse punishment than death.

Tsarnaev would be allowed to exercise, study for a college degree, even write a book, get visits, talk on the phone to family and exchange unlimited letters, they said.

Life imprisonment would be the "minimum" sentence the jury could impose, assistant US attorney William Weinreb said.

Judy Clarke, one of America's top anti-death penalty lawyers, delivered a 90-minute closing statement that stressed how Tsarnaev had expressed genuine remorse during prison visits to a famous Catholic nun.

She portrayed an impressionable youth fed Al-Qaeda magazines and lectures by his brother, the true mastermind of the attacks, son of a rootless family life, with a mentally ill father and an "intimidating," radicalized mother.

"Jahar Tsarnaev was not the worst of the worst, and that's what the death penalty is reserved for," said Clarke, using his Americanized name.

- Mitigating factors -

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

Mitigating factors include Tsarnaev's young age -- 19 at the time -- his brother's domineering influence, his parents' return to Russia in 2012, the love and care of his friends, and his reported expression of remorse.

Clarke denied claims her client would enjoy life in "the most rigid, punitive prison in America," said he would not be writing a book and urged the jury not to make him a martyr.

"With either option Jahar Tsarnaev dies in prison. The question is when and how," she said. "There's no punishment, not even a death sentence that can balance the scales."

"I ask you to choose life and impose the sentence of life imprisonment without the possibility of release," she finished.

Jurors have to complete a 24-page verdict form and discuss each sentencing count separately, leaving open the prospect of lengthy deliberations.

If they select the death penalty for just one count, that will be imposed.

"The choice between these very serious alternatives is yours and yours alone to make," O'Toole said.
Source: AFP