Washington, April 9 (IANS): A federal jury on Wednesday found 21-year-old Dzhokhar Tsarnaev, a Kyrgyzstan-born US citizen, guilty of all 30 counts related to the 2013 Boston Marathon bombing attacks, which killed three people and maimed 264 others.

Since death penalty is the possible punishment in 17 of the 30 counts, the trial will move to the next phase where the same jury will weigh whether Tsarnaev should be executed or serve life sentence in prison, Xinhua reported.

Though Tsarnaev pleaded not guilty, from the beginning of the trial, his defence team focused on convincing the jurors that he was under the influence of his dominant older brother Tamerlan, a defence tactic that was designed not to win the trial, but to avoid the death penalty.

Since the trial began on March 4, prosecutors have called 92 witnesses while the defence summoned only four.

"He was there," the leading defence lawyer Judy Clarke told jurors in her closing arguments. "We are not asking you to excuse the conduct, but let's look at the varying roles," said Clarke.

"You know who made these bombs. It was Tamerlan ...If not for Tamerlan, it (the bombing attacks) wouldn't have happened."

In her 50-minute closing argument, Clarke repeatedly referred to the fact that Tsarnaev was 19 and his older brother was 26 when the attacks happened in 2013, and called Tsarnaev "a teenager." Tamerlan died following a gunfight with police in Watertown, Massachusetts.