The trial of accused Boston Marathon bomber Dzhokhar Tsarnaev begins in earnest Wednesday, with opening statements in a capital trial that's expected to last several months. It took nearly two months to seat a jury.

The 18 jurors (including six alternates) will hear and see what prosecutors say is irrefutable evidence of Tsarnaev's role in the notorious twin bombings that killed three people and injured more than 260, as well as in the events that followed, in which a Massachusetts Institute of Technology police officer was also killed.

Tsarnaev faces 30 charges over those events in April 2013. If he's found guilty, the 21-year-old man will be punished with either a death sentence or life in prison.

From Boston, NPR's Tovia Smith reports:

"Several of the 8 men and 10 women have said they already believe Tsarnaev is guilty, but insist they can keep an open mind, and decide the case based on the evidence at trial."Today, prosecutors begin to lay that out for them. They say they have heaps of video and photos, plus evidence he downloaded al Qaeda bomb making instructions, and they say Tsarnaev's own message, left on the boat where he was hiding, shows his justification for the attack."Defense attorneys have indicated they may not challenge all the evidence, but will be focused on sentencing. They say Tsarnaev was coerced by his domineering older brother, who was the real mastermind of the attack. So, they say, Tsarnaev does not deserve the death penalty."

The jury has been under close scrutiny, with some potential members excused because they said they are morally opposed to the death penalty — and others excused because they said they wouldn't be able to keep an open mind in the case.

The case is being tried in a federal court in Boston, under Judge George O'Toole Jr., despite several efforts by the defense team to move the trial.

Member station WBUR reports:

"O'Toole rejected three change-of-venue motions, saying the process of carefully questioning jurors to detect bias was successful in finding impartial jurors. The 1st U.S. Circuit Court of Appeals twice refused to order the trial moved."

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