Matanov will be sentenced on June 18.
Watertown Police patrolman John Reynolds recalled chasing the brothers in two cars.
Tsarnaev, 21, is charged with killing three people and injuring 264 with a pair of homemade bombs.
Attorneys for Dzhokhar Tsarnaev argue an impartial jury could not be seated so close to the site of the attack.
The field of potential jurors called for the case is the largest ever summoned to Boston federal court.
Dzhokhar Tsarnaev is accused of carrying out the April 2013 bombing at the Boston Marathon with his brother.
The accused, Dzhokhar Tsarnaev, could face the death penalty if found guilty of the April 2013 Boston attack
Boston Magazine reported that a cab driver told investigators that he and Tamerlan Tsarnaev discussed the bombing.
As Dzhokhar Tsarnaev awaits trial for his alleged role in the Boston Marathon bombing, many of the women in his life are still proclaiming his innocence—and pushing for jihad
Tsarnaeva reportedly called and threatened her boyfriend's ex-girlfriend