BOSTON — Boston Marathon bomber Dzhokhar Tsarnaev had a variety of extremist materials on his computer, including an issue of the al-Qaida magazine Inspire with an article titled “Make a Bomb in the Kitchen of Your Mom,” an FBI agent testified Thursday.

Tsarnaev, 21, faces the possibility of the death penalty in the 2013 attack, which killed three people and injured more than 260.

During opening statements this month, his lawyer admitted that he participated in the bombings, but said his older brother, Tamerlan, was the mastermind who recruited a young, impressionable Dzhokhar into the plan. The defense argues that Dzhokhar does not deserve the death penalty.

Prosecutors, however, have portrayed Dzhokhar, then 19, as an active and willing participant in the bombings. Tamerlan was killed in a gun battle with police after the bombing.

On Thursday, Kevin Swindon, a supervisory special agent for the FBI’s cyber squad in Boston, reviewed the contents of Tsarnaev’s laptop computer, as well as a desktop computer at his family’s Cambridge apartment, thumb drives and other devices.

Several devices, including Dzhokhar’s computer and a thumb drive found in his dorm room at the University of Massachusetts-Dartmouth, contained issues of Inspire magazine and other radical materials, including a series of audio lectures by Anwar al-Awlaki, an American-born Muslim cleric who was suspected of being a terrorist and killed in a U.S. drone strike in Yemen in 2011.

Judy Clarke, one of Tsarnaev’s lawyers, said during her opening statement that much of the material on Tsarnaev’s computer was on subjects more common to college students, including girls, cars and homework. The defense contends that for much of the radical material cited by prosecutors, it is impossible to tell whether Tsarnaev is the one who downloaded it or if it was sent to him by others, including his brother.

In fact, the thumb drives introduced Thursday contained material that appeared to have been put on them by other Tsarnaev family members, including a pay stub of his sister-in-law and a rental agreement in her name. In the indictment against Tsarnaev, prosecutors allege he downloaded a copy of Inspire that included instructions on how to build bombs with pressure cookers, the kind of device used in the marathon bombing.