The jury weighing whether Boston Marathon bomber Dzhokhar Tsarnaev will be sentenced to death or to life in prison for the deadly 2013 attack began its first full day of deliberations Thursday on his fate.
The same 12 people, who last month found the 21-year-old guilty of killing three people and wounding 264 others at the race's crowded finish line, deliberated for about an hour on Wednesday afternoon after prosecutors and defense lawyers made their closing arguments.
"The importance of your deliberations should be obvious," US District Judge George O'Toole said in his instructions to jurors, who can only sentence Tsarnaev to death by lethal injection or life in prison without possibility of release.
Jurors have been told to weigh a list of aggravating and mitigating factors, which reprise the trial's key themes.
In the prosecution's view, Tsarnaev is an unrepentant mass killer. But the defense painted him as a hapless college kid who did the bidding of his 26-year-old brother.
Prosecutors argued that Tsarnaev is a jihadist who chose the world-renowned race as the best place to kill and maim as many people as possible, including children for whom the day is a school holiday.
They said the defendant has shown no remorse for crimes he justified as vengeance for US military campaigns in Muslim-dominated countries.
"This defendant does not want to die," Assistant US Attorney Steve Mellin said during the prosecution's closing argument on Wednesday. A death sentence, Mellin continued, "is giving him what he deserves."
Tsarnaev was convicted of murdering 8-year-old Martin Richard, 23-year-old Chinese graduate student Lingzi Lu, 29-year-old restaurant manager Krystle Campbell and Massachusetts Institute of Technology policeman Sean Collier.
Defense lawyers contend that Tsarnaev was a bright, gentle kid who ultimately could not overcome his circumstances: a mentally ill father and inattentive mother whose general neglect became acute when they left him in the United States to return to Russia in 2012, and a radical older brother, Tamerlan, the architect of the bombings.
"We're asking you to choose life, even for the Boston Marathon bomber," defense lawyer Judith Clarke said in her closing statement. "It's a sentence that reflects justice and mercy."
The jurors have been asked to return a sentence for each of the 17 death penalty-eligible crimes. A death sentence for any one offense would supersede all life sentences. All 12 jurors must reach unanimous agreement to sentence Tsarnaev to death.