Attorneys are presenting disturbing computer evidence from a Boston Marathon bomber and his widow

The sentencing phase of Boston Marathon bomber Dzhokhar Tsarnaev's trial is underway, and his attorneys are presenting evidence from his brother's computer to convince a jury that the elder of the two was the mastermind behind the attack.

Dzhokhar's defense attorneys are trying to spare him from the death penalty. They're arguing that his older brother Tamerlan influenced Dzhokhar to participate in bombing the finish line of the 2013 marathon.

Tamerlan died during the manhunt for him and Dzhokhar the week of the bombing. Three people were killed and more than 200 were injured in the attack.

Tsarnaev's attorneys also showed evidence from Tamerlan's widow's laptop, raising new questions about how much she knew about her husband's extremism before the attack.

Evidence shown in court on Tuesday shows how deeply Tamerlan was involved in radical Islam. BuzzFeed News is reporting from the courtroom:

Showing search history from the MacBook Pro, registered to Katherine Tsarnaev.

- Mike Hayes (@michaelhayes) April 28, 2015

Jan. 2012 search: "if your husband becomes a shahid what are the rewards for you?"

- Mike Hayes (@michaelhayes) April 28, 2015

Jan. 7, 2012 searches: "wife of mujahideen" "rewards for wife of mujahideen"

- Mike Hayes (@michaelhayes) April 28, 2015

"Shahid" can mean "martyr" and "mujahideen" is often used to denote an Islamic fighter.

Password on computer? Wait for it … Allahuakbar1. #Tsarnaev

- Hilary Sargent (@lilsarg) April 28, 2015

"Allahu Akbar" means "God is great" in Arabic.

Defense showing Skype messages between Tamerlan and Katherine Tsarnaev. Includes links of YouTube videos of Syrian conflict. Sent from Tam.

- Mike Hayes (@michaelhayes) April 28, 2015

Tamerlan Tsarnaev's laptop desktop is two mutilated children. Hard to look at.

- Mike Hayes (@michaelhayes) April 28, 2015

Found stickie notes in Cyrillic letters about fighting for Allah. One quote: "fighting may be imposed on you even if you don't like it."

- Mike Hayes (@michaelhayes) April 28, 2015

Tamerlan's TrueCrypt history contains a folder with an image Osama Bin Laden.

- Mike Hayes (@michaelhayes) April 28, 2015

One photo appears to show Tamerlan in a long white robe with a gun. Another photo of Tamerlan with a child and a gun.

- Mike Hayes (@michaelhayes) April 28, 2015

Tamerlan reportedly visited Dagestan, a dangerous region of Russia where radical Islam is on the rise, in 2012. Defense attorneys said he changed after this trip became obsessed with Islam.

Boston Globe reporter Patricia Wen noted that many of the pictures and videos found on Tamerlan's laptop focus on the suffering of people in Muslim nations.

In court on Monday, lawyers showed a text that Tamerlan's widow Katherine sent to a friend after the bombing. She said she was ok and that Tamerlan was at home in Cambridge, but then went on to say: "Although a lot more people are killed every day in Syria + other places. Innocent people."

Investigators are looking into how much Russell knew and when. Some bomb components were found at the home Russell shared with Tamerlan, but Dzhokhar said after police apprehended him that she wasn't part of the attack.

But it seems clear that Tamerlan influenced Russell's views significantly. Friends and her mother told the court that Tamerlan urged her to convert to Islam and that she came to embrace it.