Dzhokhar Tsarnaev, pictured in this photo presented as evidence in the trial by the U.S. Attorney's Office in Boston, has been sentenced to death. (U.S. Attoney’s Office in Boston/via Reuters)

Two years after the horrific bombing of this city’s famed marathon, a federal jury on Friday sentenced to death one of the young men responsible for the attack, turning away appeals for mercy from his attorneys and even some victims.

The jury of seven women and five men rendered its decision after deliberating for more than 14 hours. As the verdict was read, the bomber, 21-year-old Dzhokhar Tsarnaev, displayed no sign of emotion.

The outcome was a victory for prosecutors, who said the former college student worked in tandem with his older brother and carried out the attack in a “heinous, cruel and depraved manner.” Jurors rejected arguments that Tsarnaev had fallen under the sway of his brother, Tamerlan, and was remorseful over the suffering he caused.

Tsarnaev will be transferred to a federal prison, where he will remain until he is put to death by lethal injection. His attorneys did not comment after the verdict, but they are expected to appeal the sentence.

After the verdict, Karen Brassard, who was wounded in the attack, said there was “nothing happy about having to take someone’s life.” But she called the outcome “a just conclusion.”

How the prosecutors argued for the death penalty

“Right now, it feels like we can take a breath and breathe again,” she said.

Tsarnaev will become the 62nd federal inmate on death row, according to the Death Penalty Information Center. But it has been more than a decade since the federal government executed an inmate, and the Obama administration is reviewing its protocol for carrying out the death penalty after a botched Oklahoma state execution last year.

But the Justice Department, under Attorney General Eric H. Holder Jr., decided last year to seek the death penalty in Tsarnaev’s case. After Friday’s verdict was read, Holder’s successor, ­Loretta E. Lynch, issued a statement calling the sentence “the ultimate penalty” and “a fitting punishment for this horrific crime.”

Tsarnaev faced the possibility of death on 17 charges and was sentenced to death on six of them.

Prosecutors had depicted him as a cold-blooded killer, repeatedly arguing that his placement of explosives near a young child was evidence of his depravity and one of the aggravating factors that supported a death sentence. Eight-year-old Martin Richard was one of three people killed in the April 15, 2013, bombings near the finish line of the Boston Marathon.

More than 260 others were injured; 17 of them lost limbs. Tsarnaev was also charged with killing Sean Collier, a police officer employed by the Massachusetts Institute of Technology, in the aftermath of the attack. Although jurors found Tsarnaev guilty of murdering Collier, they did not sentence him to die on that count, a disappointment for prosecutors and the law enforcement community.

Throughout the trial, prosecutors emphasized the scope of the carnage to jurors, outlining the death and destruction in graphic detail.

“This is not a day of celebration. It is a day of reflection and healing,” Carmen M. Ortiz, the U.S. attorney for Massachusetts, told reporters after the verdict. “It is time to turn the page.”

Prosecutors argued that Tsarnaev and his brother — who died in a shootout with police days after the bombings — were inspired by radical Islam and moved to violence out of a sense of vengeance over the U.S. wars in Iraq and Afghanistan. In the boat where the younger Tsarnaev was eventually captured, authorities found a note: “Stop killing our innocent people and we will stop.”

“Those are the words of a terrorist convinced that he has done the right thing,” Assistant U.S. Attorney Steve Mellin told the jury. “He felt justified in killing and maiming and seriously injuring innocent men, women and children.”

In April, the jury that sentenced Tsarnaev had found him guilty of all 30 charges he faced in connection with the 2013 bombings, one of the worst terrorist attacks in the United States since the Sept. 11, 2001, hijackings.

Although Tsarnaev’s attorneys never contested that he was involved in the bombings, they mounted a vigorous defense during the penalty phase of the trial, seeking to convince jurors that mitigating factors demanded that they spare his life. Central to that argument was the notion that he was naive and impressionable — he was 19 at the time of the attack — and merely following Tamerlan, whom the attorneys depicted as the mastermind of the plot. Defense attorneys also argued that the younger Tsarnaev deeply regretted his actions.

The vast majority of the jurors did not accept those arguments. Only two found that he had “expressed sorrow and remorse for what he did and for the suffering he caused,” according to the lengthy verdict form read aloud in court. Only three jurors found that he was under the influence of his brother and would not have committed the crimes but for Tamerlan.

Tsarnaev’s legal team included attorneys with deep experience in capital cases. One of them, Judy Clarke, had previously persuaded juries to spare the lives of clients facing the death penalty, including Sept. 11, 2001, conspirator Zacarias Moussaoui.

If sentenced to life, Tsarnaev would have been held at a Supermax prison that has been described by a former warden as a “version of hell” and a place that “is not designed for humanity.” His attorneys used such descriptions to argue before the jury that a life sentence would not be a reprieve.

Clarke told the jury that a life sentence would allow “for the possibility of redemption and a greater opportunity for healing for everyone involved.”

“Mercy’s never earned, it’s bestowed,” she said. “And the law allows you to choose justice and mercy.”

Victims of the marathon bombings were divided on the sentence. Although some argued publicly that they believed Tsarnaev deserved the death penalty, others — including the family of the 8-year-old boy — called for his life to be spared. Ortiz said she took their views seriously.

For other survivors and relatives of victims, a life sentence would have proved insufficient.

Said Michael Ward, a firefighter who was watching the marathon in 2013 and who helped victims after the explosions: “This nothing to celebrate. This is a matter of justice.”

Tsarnaev “wanted to go to hell,” he said, “and he’s going to get there early.”

Mark Berman and Sari Horwitz in Washington contributed to this report.