Dzhokhar Tsarnaev has been convicted in the Boston Marathon bombing by a federal jury that now must decide whether the 21-year-old former student should be executed.
While the trial was one of the most closely watched in recent US history, Tsarnaev's conviction was practically a foregone conclusion, given his lawyer's startling admission during opening statements that Tsarnaev carried out the attack with his now-dead older brother, Tamerlan.
Tsarnaev kept his hands folded in front of him as he listened to the verdict, reached after a day-and-a-half of deliberations. He was found guilty of 30 charges that included use of a weapon of mass destruction.
Seventeen of the charges are punishable by death.
During the penalty phase, Tsarnaev's lawyers will present so-called mitigating evidence that they hope will save his life. That could include evidence about his ethnic Chechen family, his relationship with his brother and his childhood in the former Soviet republic of Kyrgyzstan and later in the volatile Dagestan region of Russia.
Prosecutors portrayed the brothers - who moved to the US from Russia more than a decade ago - as full partners in a plan to punish the US for its wars in Muslim countries. Jihadist writings, lectures and videos were found on both their computers, though the defence argued that Tamerlan downloaded the material and sent it to his brother.
The two shrapnel-packed pressure-cooker bombs that exploded near the marathon's finish line on April 15, 2013, killed three spectators and wounded more than 260 other people, turning the traditionally celebratory home stretch of the race into a scene of carnage and putting the city on edge for days.
In the next phase of the trial, the jury will hear evidence on whether Tsarnaev should get the death penalty or spend the rest of his life in prison.
In a bid to save him from a death sentence, defence attorney Judy Clarke has argued that Tsarnaev, then 19, fell under the influence of his radicalised brother.
Tamerlan, (26) died when he was shot by police and run over by Dzhokhar during a chaotic getaway attempt days after the bombing.
"If not for Tamerlan, it would not have happened," Clarke told the jury during closing arguments.
The US government called 92 witnesses over 15 days, painting a hellish scene of torn-off limbs, blood-spattered pavement, ghastly screams and the smell of sulphur and burned hair. Survivors gave heartbreaking testimony about losing legs in the blasts or watching people die.
The father of an eight-year-old boy described making the agonising decision to leave his mortally wounded son so he could get help for their six-year-old daughter, whose leg had been blown off.
Killed were Lingzi Lu, a 23-year-old Chinese graduate student at Boston University; Krystle Campbell, a 29-year-old restaurant manager; and Martin Richard, the eight-year-old. Massachusetts Institute of Technology police Officer Sean Collier was shot and killed during the brothers' getaway attempt.
Some of the most damning evidence included video showing Tsarnaev planting a backpack containing one of the bombs near where the eight-year-old was standing, and incriminating statements scrawled inside the dry-docked boat where a wounded and bleeding Tsarnaev was captured days after the tragedy.
"Stop killing our innocent people and we will stop," he wrote.
Tsarnaev's lawyers barely cross- examined the government's witnesses and called only four people to the stand over less than two days, all in an effort to portray the older brother as the guiding force in the plot.
Witnesses testified about phone records that showed Tsarnaev was at the University of Massachusetts-Dartmouth while his brother was buying bomb components, including pressure cookers.
A forensics expert said Tamerlan's computer showed search terms such as "detonator", "transmitter" and "receiver", while Dzhokhar was largely spending time on Facebook and other social media sites. Also, an FBI investigator said Tamerlan's fingerprints - but not Dzhokhar's - were found on pieces of the two bombs.
Ms Clarke is one of America's foremost death-penalty specialists and has kept other high-profile defendants off Death Row. She saved the lives of Unabomber Ted Kaczynski and Susan Smith, who drowned her two children in a lake in 1994.
Tsarnaev's lawyers tried repeatedly to get the trial moved out of Boston because of the heavy publicity and the widespread trauma. However, opposition to capital punishment is strong in Massachusetts, which abolished its state death penalty in 1984, and some polls have suggested a majority of Bostonians do not want to see Tsarnaev sentenced to die.
During the penalty phase, prosecutors will present so-called aggravating factors in support of the death penalty, including the killing of a child and the targeting of the marathon because of the potential for maximum bloodshed.