Boston Bomber Dzhokhar Tsarnaev Volunteered as Family Fell Apart, Jurors Told

Boston: Lawyers seeking to spare convicted Boston bomber Dzhokhar Tsarnaev from the death penalty called witnesses on Wednesday who described his volunteer work with disabled children, his respect for his older brother, and his father's mental illness in the years before the attack.

Tsarnaev, 21, was found guilty last month of killing three people and wounding 264 others by bombing the marathon's crowded finish line on April 15, 2013, in one of the highest-profile attacks on U.S. soil since Sept. 11, 2001. He was also convicted of killing a police officer three days later.

Defence lawyers are trying to persuade the jury in U.S. District Court in Boston to sentence Tsarnaev to life in prison without possibility of parole rather than death, asserting that he would not have bombed the marathon had it not been for his radical older brother.

The brother, 26-year-old boxer Tamerlan Tsarnaev, was killed after a gunfight with police days after the bombing.

A longtime friend of Tsarnaev's family on Wednesday told the jury that Dzhokhar was a studious youth and adored Tamerlan, who had begun to cultivate a deep interest in Islam, politics and conspiracy theories before the 2013 attack.

"Anytime Tamerlan would say 'Let's do this or that,' he would always go along. He would be a good younger brother, I would say," Elmirza Khozhugov told jurors via a remote video feed from Kazakhstan in Central Asia, where he now lives.

Khozhugov was married to the Tsarnaev's sister Ailina from 2006 to 2008 and cultivated a friendship with Tamerlan. He said Tamerlan started to change after an Armenian man named Misha began visiting the Tsarnaev family home in Cambridge, Massachusetts, to talk to him about Islam and politics.

"Conspiracy theories. He was getting into that a lot," Khozhugov said. Khozhugov said that at one point, Tamerlan gave up his favourite pastime, boxing, because Misha had told him that "in Islam hitting people on the head is not a good thing."

Prosecutors have argued Tsarnaev was an equal partner in the attack, citing Islamist propaganda found on his computer and a note he wrote that cast the bombing as retribution for U.S. military campaigns in predominantly Muslim countries.

Jurors also learned about the mental illness of Tsarnaev's father, Anzor, which progressed to the point where a doctor in 2012 said he required "constant supervision."

According to his medical records, which were read into evidence, Anzor often heard voices screaming his name, saw lizard-like creatures and animal faces, was paranoid, and could not sleep. He and Tsarnaev's mother later divorced.

At around this time, Tsarnaev was a volunteer in a programme to help children with disabilities at the Winchester Public Schools, according to the programme's leader Jennifer Callison.

"He was kind, he was respectful, he came to every event," Callison told the jury. Asked if she could have imagined Tsarnaev would bomb the marathon, she replied, "No."

Tsarnaev's high school math teacher, Eric Traub, said he also remembered Tsarnaev as a kind person> He said he was "shocked" when he learned Tsarnaev was a suspect in the bombing. "It just didn't make sense to me."

Martin Richard, 8, Chinese exchange student Lu Lingzi, 23, and restaurant manager Krystle Campbell, 29, died in the bombing. The Tsarnaev brothers also shot dead Massachusetts Institute of Technology police officer Sean Collier.