In this courtroom sketch, defendant Azamat Tazhayakov, left, a college friend of Boston Marathon bombing suspect Dzhokhar Tsarnaev, is depicted listening to testimony by FBI Special Agent Phil Christiana, right, during the first day of his federal obstruction of justice trial Monday, July 7, 2014 in Boston. Tazhayakov, of Kazakhstan, is accused with another friend of removing items from Tsarnaev's dorm room, but is not charged with participating in the bombing or knowing about it in advance. (AP Photo/Jane Flavell Collins)
In this courtroom sketch, defendant Azamat Tazhayakov, left, a college friend of Boston Marathon bombing suspect Dzhokhar Tsarnaev, is depicted listening to testimony by FBI Special Agent Phil Christiana, right, during the first day of his trial.
Jane Flavell Collins/AP photo

Azamat Tazhayakov is accused of removing items from Dzhokhar Tsarnaev’s dorm room on April 18, 2013, just days after the Boston Marathon bombings. Tazhayakov one of three friends of Tsarnaev from UMass Dartmouth accused of interfering with the bombing investigation.

A backpack that allegedly contained fireworks is a key item at issue in this case.

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Dzhokhar Tsarnaev and his brother, Tamerlan, are accused of planting two bombs near the finish line of the 2013 Boston Marathon. Tamerlan died days later after a confrontation with police. Dzhokhar Tsarnaev faces the possibility of the death penalty and is set to go on trial in November.

Dzhokhar Tsarnaev’s roommate, Andrew Dwinells, concluded his testimony in the trial Wednesday, in which he discussed what happened when Tsarnaev’s friends showed up at his dorm room on April 18, 2013.

A Homeland Security and a FBI agent specializing in computer forensics also took the stand Wednesday.

Jurors also heard from the girlfriend of Dias Kadyrbayev, who is also accused of impeding the investigation, via a videotaped interview that was shown in court.

On Tuesday, an FBI agent testified that Tazhayakov and another friend agreed to get rid of the backpack, the Associated Press reported. During cross-examination from the defense, however, the agent said Tazhayakov did not indicate he actually handled the backpack, but said Dias Kadyrbayev took it and threw it away.

The agent also testified that Tazhayakov initially denied knowing what was in the backpack, but later said he saw fireworks that appeared to be emptied of powder.

In his testimony on Tuesday, Dwinells said a person, identified as Kadyrbayev, grabbed a bag of marijuana from a drawer and one person grabbed a pair of headphones, but said he did not see any other items being removed.

Prosecutors allege Tazhayakov, Kadyrbayev and another friend went to Tsarnaev’s dorm room after Tsarnaev texted Kadyrbayev and said they could ‘‘take what’s there.’’

Tazhayakov, 20, has pleaded not guilty to obstruction of justice and conspiracy charges. His trial is expected to take three weeks.

Here’s what was reported from the courtroom:

Here’s what happened on day 1 of the trial