Grisly testimony at Boston bombing trial as prosecutors rest their case

BOSTON (AFP) - US prosecutors rested their case Monday in the trial of Boston bombing suspect Dzhokhar Tsarnaev after gruesome testimony about the death of the youngest victim left some jurors in tears.

Defence attorneys began calling witnesses after the emotional finale to the government's case against the 21-year-old Tsarnaev, who could face the death penalty if convicted over the April 15, 2013 attack.

Three people were killed and 264 others wounded in the blasts at the city's marathon - the worst in the United States since the September 11, 2001 attacks on the World Trade Centre and the Pentagon.

Prosecutors summoned 92 witnesses to the stand in recent weeks, building a case against Tsarnaev as an active and willing participant in the bombings that ripped through crowds gathered near the race's finish line.

Their final witness was medical examiner Henry Nields, who recounted in graphic detail the injuries suffered by the youngest victim, eight-year-old Martin Richard, who was torn apart by one of the pressure-cooker bombs.

The child's blood-stained clothing was shown to jurors, some of whom were unable to hold back tears.

"He was eight years old," Nields reiterated.

Jurors also were shown photographs of the Richard family, standing on the race's sidelines in front of Tsarnaev.

Another photo showed the boy lying on the ground after the attacks, in which his younger sister Jane also lost a leg.

The boys' parents, Denise and Bill, were in the courtroom.

At the start of the trial defence lawyer Judy Clarke acknowledged the role of Tsarnaev - an American citizen of Chechen descent - and his elder brother Tamerlan were responsible for the carnage.

But Clarke put the bulk of the blame on the elder Tsarnaev, who was killed in a shootout with police following the blasts.

"It was Tamerlan Tsarnaev who self-radicalised. It was Dzhokhar who followed," Clarke said during opening statements.

Tsarnaev has pleaded not guilty to 30 charges over the attacks, the murder of a police officer, a carjacking and the shootout with police while on the run.

Seventeen of those charges carry the possibility of the death penalty under federal law.

During nearly four weeks of testimony, prosecutors painted the picture of a cold, callous killer - a marijuana-smoking, laid-back student who had recently failed a number of exams and become an avid reader of the Islamist literature that investigators found on his computer.

Jurors were shown a video of Tsarnaev casually buying milk just 30 minutes after the bombings, They were also shown a message left by Tsarnaev inside a boat, the bolthole where he was arrested four days after the attacks, that appeared to justify the attacks by criticising the US government over the wars in Iraq and Afghanistan.

Tsarnaev was hard to read on Monday, as he has been throughout the trial, with his head sometimes lowered as witnesses testified. He occasionally spoke with Clarke.

If Tsarnaev is found guilty, jurors will determine in a sentencing phase whether he will receive the death penalty or life in prison.