BOSTON (Reuters) - The Boston bombing trial will dig deeper on Tuesday into a question that could spell the difference between life or death for suspect Dzhokhar Tsarnaev: was he a homegrown violent extremist or a patsy influenced by his older brother?
Counter-terrorism expert Matthew Levitt will resume his testimony after he took the stand on Monday drawing comparisons between Al Qaeda propaganda found on Tsarnaev's computer and some of his own words in social media and the note he scrawled before his capture.
Tsarnaev, 21, is accused of killing three people and injuring 264 with a pair of homemade pressure-cooker bombs at the Boston Marathon's crowded finish line on April 15, 2013, and with fatally shooting a police officer three days later as he and his 26-year-old brother, Tamerlan, tried to flee.
His defense attorneys opened the trial March 5 admitting he committed the crimes, but are seeking to spare him the death penalty by painting him as a mostly normal American kid who fell under the spell of his brother, who was killed after a shootout with police days after the bombing.
On Monday, Levitt, a senior fellow at a Washington think-tank and a former U.S. intelligence agent, placed the marathon bombing in the context of a "global jihad movement" bent on attacking America.
He said that the rise of social media had made it easier for extremist groups to radicalize young Muslims in the United States and elsewhere, and encourage them to either fight in foreign wars or attack at home.
He said some of Tsarnaev's Twitter posts and the message he wrote on the inside of a dry-docked boat where he was finally captured in a hail of bullets showed similarities to Al Qaeda lectures and literature found on his laptop.
"We Muslims are one body you hurt one you hurt us all," the message inside the boat read, citing aggression in Muslim lands.
Levitt also said a Twitter post Tsarnaev wrote the day of the 2012 Boston Marathon: "They will spend their money and they will regret it and then they will be defeated," closely resembled part of a lecture by late U.S.-born Al Qaeda figure Anwar al-Awlaki found on his computer.
Tsarnaev's defense attorneys did not have an opportunity to cross-examine Levitt on Monday, but have argued that it is unclear where files on Tsarnaev's computer, including instructions for building a bomb, originated.
Separately, a citizen of Kyrgyzstan is due to plead guilty on Tuesday on charges of lying to investigators probing the bombing. The man, Khairullozhon Matanov, was a friend of the Tsarnaev brothers but played down how well he knew the pair.
(Reporting by Richard Valdmanis; Editing by James Dalgleish)