File Photo: Boston Marathon Bombing prime accused Dzhokhar Tsarnaev (AP Photo)
US jurors will deliberate for a second day in the Boston bombings trial having failed to reach a unanimous verdict in more than seven hours on Tuesday, the judge said.
Three people were killed and 264 others wounded in the twin blasts at the city's marathon in 2013, the worst attack in the United States since the September 11, 2001 attacks on New York, Washington and Pennsylvania.
Government prosecutors portrayed Muslim immigrant Dzhokhar Tsarnaev, who became a US citizen in 2012, as a callous terrorist who carried out the April 15, 2013 bombings to punish the United States.
Tsarnaev's lawyers admit that he planted one of the bombs hidden in a backpack, but cast him as a feckless accomplice, bullied or manipulated into taking part by his more radical elder brother.
Tsarnaev, 21, looked pale and tired as Judge George O'Toole sent the 12 jurors home for the night and instructed them to return on Wednesday.
O'Toole said the jury had submitted two questions to the court, which would be answered on Wednesday.
The seven women and five men must agree a verdict on 30 separate counts -- many of which have multiple sub-clauses -- over the attacks, the murder of a police officer, a car jacking and a shootout while on the run.
Seventeen of the charges carry the possibility of the death penalty.
The jury began deliberations at 9:15 am (1315 GMT) following a month-long first stage of the trial. They have already deliberated longer than the defense took to present just four witnesses during the 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.