BOSTON — An F.B.I. agent told a federal court here on Tuesday that Azamat Tazhayakov, a college friend of the surviving Boston bombing suspect, Dzhokhar Tsarnaev, agreed that a backpack found in Mr. Tsarnaev’s dorm room in the days after the bombing should be thrown away.
It was the second day of the trial of Mr. Tazhayakov, 20, who is accused, along with his friend Dias Kadyrbayev, of hindering the investigation into the bombing at the Boston Marathon on April 15, 2013. Prosecutors are seeking to prove that the two men entered Mr. Tsarnaev’s room on April 18, believing him to be the bombing suspect; removed several items, including a laptop and the backpack, which contained fireworks; and agreed to dispose of the backpack, which was later found in a landfill.
Mr. Kadyrbayev’s trial is scheduled for September. Both men face one count each of obstruction of justice and conspiracy; the obstruction charge carries a sentence of 20 years in prison, and conspiracy five years.
While on the stand Tuesday, the agent, Sara Wood, who interviewed Mr. Tazhayakov at a state police barracks for four and a half hours on April 19, said Mr. Tazhayakov told her that he had been present when Mr. Kadyrbayev found the backpack in Mr. Tsarnaev’s room, and that he was scared when he realized that what he called “gunpowder” was missing from an opened firework.
Ms. Wood said Mr. Tazhayakov described Mr. Kadyrbayev as pacing once they returned home with the backpack.
“He said he agreed to throwing the backpack out,” Ms. Wood said to Matthew Myers, a lawyer representing Mr. Tazhayakov.
Mr. Myers tried to cast doubt on Ms. Wood’s testimony, emphasizing that Mr. Tazhayakov’s interview was not recorded and that his client did not provide a written statement to the authorities. Mr. Tazhayakov’s defense team contends that Mr. Kadyrbayev removed the backpack from the room and says evidence does not show that Mr. Tazhayakov agreed to dispose of it.
Also testifying Tuesday was Andrew Dwinells, Mr. Tsarnaev’s roommate at the University of Massachusetts, Dartmouth. Mr. Dwinells said Mr. Tsarnaev’s behavior did not change much in the days after two bombs exploded near the finish line of the marathon, killing three people and wounding more than 260.
“He slept a little bit more, but that was it,” Mr. Dwinells, an engineering student, said.
A version of this article appears in print on July 9, 2014, on page A16 of the New York edition with the headline: Testimony in Boston Bomb Trial Focuses on Backpack.
Matthew Myers for the Defense.