A US federal judge has began the process of selecting the jury that will hear the trial of accused Boston Marathon bomber Dzhokhar Tsarnaev.

Tsarnaev could get the death penalty if convicted of killing three people and injuring more than 260 others by detonating a pair of homemade bombs placed amid a crowd of thousands of spectators at the race's finish line on April 15, 2013.

The 21-year-old ethnic Chechen and naturalised US citizen has pleaded not guilty to all 30 charges against him.

Tsarnaev sat quietly between his lawyers during Monday's proceedings, looking down and fidgeting. He did not speak but nodded curtly at jurors when the judge pointed him out.

US District Judge George O'Toole acknowledged that people picked to be among the 12 jurors and six alternates will be aware of the bombing, but reminded prospective jurors that their job during the trial, expected to last three to four months, would be to consider only the evidence presented in court.

The judge told two groups of prospective jurors, each numbering around 200 people, that Tsarnaev is charged in connection with the marathon bombing and the fatal shooting of a police officer three days later.

O'Toole is allowing about three weeks for selection of the jury that will determine both Tsarnaev's guilt and whether he would be sentenced to death if convicted. The judge said opening statements by prosecutors and defense lawyers would begin around January 26.

Defense attorneys had sought to have the proceedings moved out of Boston. They argued it would be impossible to find an impartial local jury because of intense news coverage and the fact that thousands of people attended the race or hid in their homes during a day-long lockdown in the greater Boston area after the bombing.

But O'Toole and a federal appeals court blocked the request.

Tsarnaev was arrested four days after the bombing. Prosecutors say he and Tamerlan Tsarnaev, his 26-year-old brother, also shot and killed a university police officer. The brother died after a wild gun battle with police.

According to prosecutors, Dzhokhar Tsarnaev wrote messages inside of the hull of the drydocked boat where he was discovered hiding four days after the attack indicating political motivation.

The messages allegedly included "the US government is killing our innocent civilians" and "I can't stand to see such evil go unpunished," according to court papers.

Source: Al Jazeera and agencies