For the first time, the jury of the Boston Marathon bombing trial viewed video taken by security cameras near the finish line on Boylston Street showing defendant Dzhokhar Tsarnaev and his brother at the scene of the blasts.

Surveillance video and images show the defendant walking with a backpack that prosecutors contend held a bomb, leaving it in a crowd in front of a restaurant, making a brief phone call and walking away shortly before the blast.

Tsarnaev, 21, is accused of killing three people and injuring 264 at the famed race's crowded finish line on 15 April 2013.

Defence lawyers argue that Tamerlan Tsarnaev, 26, Dzhokhar Tsarnaev's brother, who died following a shoot-out with police three days after the bombing, was the driving force behind the attack, with Dzhokhar following along out of a sense of submission. By pinning the bulk of the blame on the older brother, defence lawyers hope to persuade the jury in US District Court in Boston not to sentence their client to death.

Prosecutors maintain that the defendant read jihadist magazines online and "believed that he was a soldier in a holy war against Americans".

On Monday (9 March), they showed messages from a pair of Twitter accounts that Tsarnaev maintained, according to FBI agent Stephen Kimball.

Tsarnaev, an ethnic Chechen, also briefly maintained a second Twitter account focused on Islam using the handle and the screen name "Ghuraba," Kimball said.

"Ghuraba means strangers. Out here in the West we should stand out among the non-believers as one body," Tsarnaev tweeted, according to Kimball.

Despite his lawyers' admission of responsibility, Tsarnaev has not changed his plea from not guilty.