A US jury late yesterday sentenced Boston Marathon bomber Dzhokhar Tsarnaev to death for helping to carry out the 2013 attack that killed three people and injured 264 at the world-renowned race, taking 15 hours to reach a decision.

The federal jury chose death by lethal injection for Tsarnaev, 21, over its only other option: life in prison without possibility of release.

The same panel last month found the ethnic Chechen guilty of placing a pair of homemade pressure-cooker bombs at the race’s crowded finish line on April 15, 2013, as well as fatally shooting a policeman. The bombing was one of the highest-profile attacks on US soil since September 11, 2001.

During 10 weeks of testimony, the jury heard about 150 witnesses, including people whose legs were torn off by the shrapnel-filled bombs. William Richard, the father of bombing victim Martin Richard, described the gut-wrenching decision to leave his eight-year-old son to die of his wounds so that he could save the life of his daughter, Jane, who lost a leg but survived.

Prosecutors described Tsarnaev as an adherent of al-Qaeda’s militant Islamist views who carried out the attack as an act of retribution for US military campaigns in Muslim-dominated countries.

Defence attorneys opened the trial on March 5 with the admission that Tsarnaev committed all the crimes he was accused of. But they argued that he was a junior partner in a scheme hatched and driven by his 26-year-old brother, Tamerlan, who died after a gunfight, which ended when Dzhokhar ran him over with a stolen car.