Boston Bombings Trial Hears Closing Arguments

Boston bomber Dzhokhar Tsarnaev is a callous terrorist who carried out the 2013 attack to wage holy war and punish America, a prosecutor told jurors Monday as the young Muslim's trial neared an end.

Three people were killed and 264 others wounded in the twin blasts at the city's marathon -- the worst attack in the United States since the September 11, 2001 attacks on New York, Washington and Pennsylvania.

Tsarnaev's defense admit that he took part in the attack, but have sought to portray him during the trial as a helpless accomplice, bullied or manipulated into participation by his more radical elder brother.

However prosecutor Aloke Chakravarty painted Tsarnaev as a full and willing participant in the bombing as the government closed its case on Monday.

"He wanted to terrorize this country. He wanted to punish America for what it was doing to his people," assistant US attorney Chakravarty told the court in an emotional closing statement after a one-month trial.

Tsarnaev, a Muslim American of Chechen descent who was a 19-year-old university student at the time, faces the death penalty or life behind bars without the possibility of parole if convicted.

"That day they felt their were soldiers, that they were mujahideen and they were bringing their battle to Boston," added Chakravarty.

Prosecutors spent four weeks building their case, calling 92 witnesses in an effort to paint Tsarnaev as an active and willing bomber alongside his elder brother, who was killed while on the run.

They portrayed 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.

Chakravarty showed the jury photographs and video clips, filling the court with the screams of victims, as the camera closed in on blood on the ground, the panic, fear and chaos after the April 15, 2013 attacks.

"There was nothing about this day that was a twist of fate. This was a cold, calculated terrorist act. It was intentional. It was bloodthirsty."

Prosecutors say Tsarnaev carried out the attacks to avenge the deaths of fellow Muslims overseas after learning how to build pressure-cooker bombs through Al-Qaeda English-language magazine "Inspire."

Jurors were shown photographs of Tsarnaev casually buying milk just minutes after the bombings, then laughing and joking with friends.

'He did what terrorists do'

Chakravarty read aloud from a message he left in a boat in a suburban garden, the hideout where the defendant was eventually arrested, criticizing the US government over the wars in Iraq and Afghanistan.

Defense lawyer Judy Clarke, who has saved some of America's most notorious convicts from the death penalty, said Tsarnaev deserved to be condemned but that the attacks would never have happened without Tamerlan.

Her team portrayed the older Tamerlan -- who was killed by police while on the run after the attacks -- as the architect of the bombings, arguing that his younger sibling had fallen helplessly under his influence.

Tamerlan built the bombs, murdered police officer Sean Collier, downloaded the bomb-making instructions, brought the bomb materials, the backpacks and his finger prints were all over the evidence, she said.

"Let's be honest about what the evidence actually shows. We're not asking you to excuse the conduct but lets look at he varying roles," Clarke said.

"He was an adolescent drawn into the passion and belief of his older brother and still living a teenage life. He was flunking out of school and making up lame excuses about why he was failing," she said.

Tsarnaev, she said, deserved to be condemned but she asked them to keep their minds open for the next stage of trial.

If Tsarnaev is convicted, the trial will enter a second stage when the jury determines whether he should be executed or spend the rest of his life behind bars without parole -- the only sentencing options available.

Federal Judge George O'Toole instructed the 18-person jury on the charges earlier on Monday and is still to advise the jury further on the evidence, before they retire to deliberate.

Tsarnaev had pleaded not guilty to 30 separate counts related to the April 15, 2013 attacks, and the subsequent murder of a police officer, a car jacking and a shootout with police while on he was on the run.

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