By Jim Armstrong, WBZ-TV

BOSTON (CBS) – If Dzhokhar Tsarnaev’s life online dominated the first phase of the trial, it will be his older brother’s that overpowers the second.

On Monday, the Boston Marathon bombing jury saw videos and links either from Tamerlan Tsarnaev’s YouTube page, or forwarded to his younger brother, or both.

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The defense is using them to support its theory that it was Tamerlan behind the bombings and all that followed.

In his opening statement, defense attorney David Bruck asked jurors, “If Tamerlan hadn’t been in the picture, would Dzhokhar have done this on his own? Dzhokhar did not defy Tamerlan to his face.”

The defense explained how a Cambridge mosque was the scene of two angry outbursts by Tamerlan Tsarnaev in the months leading up to the bombings. Tamerlan at the time shouted down his imam for preaching about how Muslims should get along with people in America.

The imam himself, Loay Assaf, took the stand to describe how frightening and unusual it was for an angry, muscle-bound Tamerlan to interrupt prayers by yelling out.

Tamerlan’s mother-in-law, Judith Russell, also testified. She told jurors her daughter Katherine fell under Tamerlan’s control, turning to Islam after she got close to him.

“I didn’t really want her to be with him,” Judith Russell testified. “They weren’t really a good match.”

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Another high school acquaintance of the Tsarnaev brothers, Robbie Barnes, recalled Tamerlan becoming increasingly religious ready to argue in defense of Islam.

The defense team also called to the stand Abderrazak Razak, a Cambridge Muslim shopkeeper who Tamerlan screamed at for selling turkey at Thanksgiving; the older Tsarnaev, Razak testified, told him that it wasn’t proper for a Muslim to celebrate Western holidays.

Tamerlan’s influence is just one of the defense’s reasons for asking the jury to sentence Dzhokhar to life in prison, rather than death.

“One punishment is over quickly; the other will last for years and decades while he is locked away,” Bruck told juries.

He added: “We’ve now seen more pain and more horror and more grief in this courtroom than any of you would have thought possible. It now falls to you to to decide what is the best and the most appropriate punishment.”

He also showed them photos of the supermax facility in Colorado likely to house Tsarnaev, telling them life here would protect the public from the convicted killer.

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“We are asking you to punish Dzhokhar by imprisoning him for the rest of his life,” Bruck said. “Whether you vote for death is up to each one of you. The law never requires you to vote for death.”