By Scott Malone
BOSTON, May 13 (Reuters) - Federal prosecutors and lawyers for the Boston Marathon bomber are set to make their final arguments on Wednesday on whether Dzhokhar Tsarnaev should be sentenced to death or to life in prison without possibility of release for the 2013 attack.
Following closing statements, the same jury that last month found the 21-year-old ethnic Chechen guilty of killing three people and injuring 264 in one of the highest-profile attacks on U.S. soil since Sept. 11, 2001 will begin deliberations on Tsarnaev's fate.
The two sides have painted sharply contrasting portraits of the convicted bomber, who has been a subdued, stoic presence in Boston's federal courthouse since the guilt phase of his trial began in early March.
Prosecutors have portrayed Tsarnaev, who immigrated to the United States from Russia a decade before the attack, as an adherent of al Qaeda's militant Islamic ideology who wanted to "punish America" with a homemade pair of pressure-cooker bombs on April 15, 2013.
During the sentencing phase of his trial, they called witnesses including people whose legs were torn off by the bombs and a trauma surgeon who worked on some of the people killed by the blasts.
Defense attorneys, meanwhile, described Tsarnaev as an adrift teenager under the spell of his 26-year-old brother, Tamerlan, who they contend was the architect and driving force behind the bombing and the murder three days later of a police officer.
Tamerlan died in the chaotic hours that followed that slaying, after a gunfight with police that ended when a fleeing Dzhokhar inadvertently ran him over with a car.
Tsarnaev's lawyers over the past week called witnesses including some of his Russian family members, who remembered him as a beloved child, and a Roman Catholic nun and well-known death penalty opponent who said she believed Tsarnaev was "genuinely sorry" for the pain the attack caused.
The jury heard from about 150 witnesses through the trials' two phases but never through Tsarnaev himself, who sat quietly and showed no emotion, other than a brief moment last week when he dabbed at his eyes when his 64-year-old aunt broke down in tears on the witness stand and was unable to testify.
The death penalty remains unpopular in Massachusetts, where it is not allowed under state law, and polls have showed more residents are opposed to the idea of putting Tsarnaev to death than in support.
Their ranks include the family of 8-year-old Martin Richard, the youngest person to die in the blasts and the sister of Massachusetts Institute of Technology police officer Sean Collier, who was shot dead by the Tsarnaevs.
The other two people killed in the bombing were 23-year-old Chinese graduate student Lingzi Lu and 29-year-old restaurant manager Krystle Campbell. (Reporting by Scott Malone; Editing by Bernard Orr)