The federal jury that watched Dzhokhar Tsarnaev sit impassively in court for the past three months delivered the severest form of justice Friday, sentencing the homegrown terrorist to death for detonating a bomb amid Boston Marathon spectators that left wounds — emotional and physical — that will persist across lifetimes.
Tsarnaev again stood stonefaced as the verdict was read by a court clerk and some stern-faced jurors dabbed their eyes. He becomes the first terrorist condemned to death by a jury in the United States in the post-9/11 world.
The unanimous verdict brought to a close a legal drama that has unfolded on the South Boston waterfront since January, with searing testimony about the bombings that killed three, took the limbs of 17 others, and injured hundreds more. Throughout the proceedings, the lanky 21-year-old showed no remorse.
The death sentence automatically sets in motion an appeals process that could last more than a decade.
"Our thoughts should now turn away from the Tsarnaev brothers for good," US Attorney Carmen M. Ortiz told reporters not long after the verdict was announced. "It is time to turn the page in these chapters."
Boston Police Commissioner William Evans also praised the verdict.
"I think we sent a strong message that we're not going to tolerate terrorism. They're not going to blow up our Marathon, they're not going to blow up our city, we're not going to tolerate terrorism in our country, and that's the strong message we sent here today."
The jury of seven women and five men deliberated for 14½ hours over three days before reaching its verdict. Some jurors were visibly shaken as the verdict was read and the judge thanked them for their service. They did not seem to look at Tsarnaev.
The jury's call for the ultimate punishment comes in a state and city that polls show to be overwhelmingly against the death penalty.
Tsarnaev was escorted from the courtroom by US Marshals. He will return to the federal courthouse in South Boston for an official sentencing hearing, which has not been scheduled. Victims of his crimes will be able to confront him at that hearing, and Tsarnaev will also be allowed to address US District Judge George A. O'Toole Jr. if he chooses.
Tsarnaev did not testify during his trial, leaving him an inscrutable figure to the jury that decided his fate.
Before revealing Tsarnaev's sentence, the clerk read through the jury's findings in a 24-page verdict sheet. Jurors had to weigh aggravating and mitigating factors for 17 death penalty eligible counts for which Tsarnaev had been convicted. They needed to find only that Tsarnaev deserved a death sentence for one of the counts, and the courtroom went quiet as the clerk announced the jury's finding that "death is the appropriate sentence for Dzhokhar Tsarnaev."
In the end, the jury sentenced Tsarnaev specifically for the bomb he placed in front of the Forum restaurant on Boylston Street that killed 8-year-old Martin Richard and Lingzi Lu, a 23-year-old Boston University graduate student from China.
The jury chose life sentences for the charges Tsarnaev faced that related to the bomb that was placed by his older brother, Tamerlan — the bomb that killed Krystle Marie Campbell, 29, of Arlington. They also did not impose a death sentence on the charges that involved the fatal shooting of MIT police officer Sean Collier.
Krystle Campbell's father, William Campbell, who testified during the trial, said Friday that he was pleased with the jury's decision. "I think the system worked, and the jury did their job," he said.
Liz Norden, whose two sons each lost a leg in the attacks, added, "I feel like a weight has been lifted off my shoulder. I don't think there were winners, but there was justice."
Present in the courtroom Friday were Richard's parents, Bill and Denise, who made a powerful statement last month when they publicly called for Ortiz to take the death penalty off the table, saying it would be better to let Tsarnaev serve life in prison so that he would no longer be in the public eye. They did not comment after the sentence was read, and were solemn as the verdict was announced.
Ortiz reiterated Friday that several factors played into the decision to seek the death penalty, such as the nature of the crime and the targeting of the Marathon — a cherished city tradition. Tsarnaev had written before his capture that the killing of innocent civilians was justified for retribution against American policy in Muslim lands, making the bombing a crime of terrorism that warranted the death penalty.
"It was a political crime designed to intimidate and coerce the United States," Ortiz said.
Vince Lisi, special agent in charge of the Boston FBI, which led the investigation into the bombing, told reporters, "Our investigation was so thorough and exhaustive, that if anybody had anything to do with these bombings, we brought them to justice — that means these two brothers."
Tsarnaev was convicted last month of 30 charges related to the Marathon bombings; the killing of MIT police officer Sean Collier; and a firefight with police in Watertown that left a Transit Police officer gravely wounded. The first phase of the trial to determine Tsarnaev's guilt included 16 days of testimony from 95 witnesses, including some who were injured in the Marathon blasts, and family members and friends of those killed.
Bill Richard told jurors how he had to leave Martin, while his wife, Denise, tended to their dying son, so that he could help his youngest child Jane, who lost a leg.
Danling Zhou described the terrified look on Lu's face after the blasts, when her abdomen was torn through. And Karen Rand McWatters, who lost a leg in the bombing, testified that she held hands with Campbell, who had softly said that her legs hurt. Campbell eventually let go of McWatters's hand.
"She never spoke again after that," McWatters said.
Because Tsarnaev was convicted of 17 capital crimes, the same jury that convicted him was required to determine his sentence in a separate phase, and over 11 days of testimony jurors heard from more than 60 witnesses.
Most of the witnesses were called by the defense, as lawyers sought to portray Tsarnaev's older brother and accomplice, Tamerlan, who was 26 at the time, as the mastermind of the attacks, and several witnesses testified to Tamerlan's quick anger and his growing obsession with a radical interpretation of Islam.
Other witnesses described Tsarnaev's troubled upbringing in an immigrant Chechen family that held to cultural traditions that gave deference to the oldest brother in a family.
Tsarnaev's family moved to the United States when he was 8, and he became a US citizen in 2011. By then, however, his father, Anzor, had grown mentally ill, his mother, Zubeidat, turned to radical Islam, and so did his older brother, according to the testimony.
Tsarnaev's parents returned to Russia in 2012, leaving behind what Tsarnaev's lawyers called an "invisible child," and the Jihad-driven Tamerlan was the only adult figure in his life, according to defense testimony.
But jurors rejected the idea that Tsarnaev's background — or his brother's influence — led him to carry out the attacks.
In the death penalty stage of the trial, jurors were required to consider mitigating factors cited by the defense team in an attempt to show Tsarnaev was less culpable and less deserving of death.
Few jurors found that Tsarnaev was vulnerable to his brother's manipulation or that Tamerlan influenced him at all. And none was convinced that any factor outweighed the prosecution's case. Only two jurors found that Tsarnaev had expressed remorse.
Judy Clarke, one of Tsarnaev's lawyers, had asked the jury to bestow mercy on her client in her closing arguments.
"A sentence of life in prison without the possibility of release allows for hope," she pleaded. "Mercy's never earned; it's bestowed. And the law allows you to choose justice and mercy."
The defense team would not comment when leaving the courthouse Friday.
Jenna Russell of the Globe staff contributed to this report. Milton J. Valencia can be reached at mvalencia
@globe.com. Follow him on Twitter @miltonvalencia.