By Scott Malone and Elizabeth Barber

BOSTON (Reuters) - The jury in the Boston Marathon bombing trial on Wednesday began deliberating whether to sentence Dzhokhar Tsarnaev to death or to life in prison for the 2013 attack that killed three people and injured 264.

Federal prosecutors wrapped up their case by arguing that the 21-year-old ethnic Chechen was a terrorist who wanted to punish America in one of the highest-profile attacks on U.S. soil since Sept. 11, 2001.

Defense attorneys, meanwhile, contended Tsarnaev was in the thrall of his 26-year-old brother, Tamerlan, who conceived and drove the attack and that he deserved to spend the rest of his life in prison without the possibility of release but not to die by lethal injection.

Citing a note that Tsarnaev wrote while hiding in a boat, bleeding, after a gunfight with police four days after the April 15, 2013, attack, Assistant U.S. Attorney Steven Mellin said Tsarnaev had turned against the country he moved to from Russia with his family a decade before the bombing.

"He wrote, 'Now I don't like killing innocent people, but in this case it is allowed because America needs to be punished.' ... These are the words of a terrorist who is convinced he did the right thing," Mellin said.

"He killed indiscriminately to make a political statement. ... His actions have earned him a sentence of death."

Mellin showed the same jury that last month found Tsarnaev guilty photos of the bombing's immediate aftermath, with victims whose legs were blown off sitting in pools of blood, and another image of a 29-year-old restaurant manager screaming in pain before she died of her injuries.

The defense, meanwhile, described Tsarnaev as a teenager adrift and under the spell of his older brother without whom, they contended, their client would never have set off a bomb or murdered a police officer.


Defense attorneys noted that when Dzhokhar's parents returned to their native Russia in 2012, he was left under the influence of Tamerlan, who had become obsessed with becoming a jihadist. Tamerlan also briefly returned to Russia.

"The horrific events of the Boston Marathon bombing cannot be told or understood with any degree of reality without talking about Tamerlan," defense attorney Judith Clarke told jurors. "Tamerlan left the United States wanting to wage war. He was rejected as a warrior. ... He came back to the United States as a jihadi wannabe. He couldn't fit into any movement, so he would create his own."

Clarke showed a photo of Tamerlan wearing an Arab headdress and holding a handgun in front of a white flag with Arabic writing. She noted that Tamerlan and the Tsarnaevs' mother, Zubeidat, both stunned their family back in Russia when they turned to militant Islam.

Tamerlan died in the chaos that ensued after a gunfight with police that ended when a fleeing Dzhokhar inadvertently ran his brother over with a stolen car.

Federal prosecutors rejected the idea that obedience ran deep in the Tsarnaev family, noting that the brothers' father, Anzor, went again his family's wishes by marrying a member of the Avar ethnic group and that Tamerlan did the same when he married an American woman who had been raised Christian but later converted to Islam.

"He's the one on trial, not his brother," Assistant U.S. Attorney William Weinreb said of Dzhokhar. "You need to sentence him for his actions."

The jury must determine whether Tsarnaev deserves to be sentenced to death or to life in prison for each of the 17 capital counts of which he was convicted. The jury need only sentence him to death for one of those counts for him to face the possibility of execution.

Defense lawyers would likely immediately appeal a death sentence.

The death penalty is unpopular in Massachusetts, where it is not allowed under state law, and opinion polls show more residents oppose the idea of putting Tsarnaev to death than support it.

Their ranks include the family of 8-year-old Martin Richard, the youngest person to die in the blasts, and the sister of Massachusetts Institute of Technology policeman Sean Collier, who the Tsarnaevs shot dead.

The other two people killed in the bombing were 23-year-old Chinese graduate student Lingzi Lu and 29-year-old Krystle Campbell.

While admitting, as she had in the trial's first day, that Dzhokhar committed all the crimes with which he was charged and then convicted, defense attorney Clarke said the bombing would not have occurred without Tamerlan.

"Dzhokhar Tsarnaev is not the worst of the worst. And that's what the death penalty is reserved for, the worst of the worst," she said. "A sentence of life in prison without possibility of release reflects justice and mercy. Mercy is never earned, it is bestowed. And the law allows you to choose justice and mercy."

(Reporting by Scott Malone; Editing by Bernard Orr, Jonathan Oatis and James Dalgleish)