By Scott Malone
BOSTON (Reuters) - Defense lawyers will begin to present their case Monday that a jury should sentence convicted Boston Marathon bomber Dzokhar Tsarnaev to life in prison rather than death, as the trial enters a new and critical stage.
Tsarnaev, a 21-year-old ethnic Chechen, was found guilty early this month of killing three people and injuring 264 in one of the highest-profile attacks on U.S. soil since Sept. 11, 2001, as well as fatally shooting a police officer.
During the initial stage of his trial, prosecutors portrayed him as an extremist who wanted to "punish America" for military campaigns in Muslim-dominated countries and who followed a blueprint from al Qaeda's "Inspire" magazine to build the homemade pressure-cooker bombs that ripped through crowds of spectators, volunteers and athletes on April 15, 2013.
Defense lawyers have countered that Tsarnaev, 19 at the time of the attack, was adrift and following the lead of his 26-year-old brother, Tamerlan, who died after a gunfight with police four days after the bombing.
One of his lead attorneys, Judith Clarke, opened the trial with the blunt admission that "it was him," Tsarnaev, who committed all the crimes he was charged with.
But she closed the guilt phase by arguing that, when it came to planning the attack and building the bombs, "Tamerlan did that."
The death penalty remains highly controversial in Massachusetts, where state law does not allow the punishment to be applied, though Tsarnaev could face it because he is on trial in federal court.
A Boston Globe survey released Monday found that just 19 percent of Massachusetts residents support the idea of putting Tsarnaev to death, fewer than the 30 percent who support the death penalty for "heinous" crimes. The poll of 804 people conducted April 22 and 23 has a margin of error of 3.5 percentage points.
In sharp contrast to the last phase of the trial, when the defense took just two days to call four witnesses, the court has scheduled about two weeks worth of testimony as Tsarnaev's lawyers make the case to spare his life.
Few details are known about who defense lawyers will call to testify as all witness lists in this trial have been filed under seal.
Some members of Tsarnaev's family have arrived in Boston but have been kept under tight guard at an area hotel, according to local media.
It is not clear exactly which members of his family traveled to Boston, and whether they will testify or simply observe the proceedings.
Another unanswered question is whether Tsarnaev will speak in his own defense. He has been a quiet presence during the trial, offering no signs of emotion as the jury heard sometimes tearful testimony from survivors and viewed graphic, disturbing images of the bombs' detonation and aftermath.
Martin Richard, 8, Chinese exchange student Lu Lingzi, 23, and restaurant manager Krystle Campbell, 29, died in the bombing. The Tsarnaev brothers shot dead Massachusetts Institute of Technology police officer Sean Collier three days later.
(Editing by Andrew Hay and Bernadette Baum)