The jury has found Robel Phillipos, a friend of Boston Marathon bombing suspect Dzhokhar Tsarnaev, guilty on both counts of lying to investigators.
Phillipos has also been found guilty of impeding a terrorist investigation by making false statements.
The jury deliberated for 34.5 hours before reaching a decision.
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With this verdict, Phillipos faces a maximum of 16 years in prison. Sentencing has been set for Jan. 29.
Phillipos was charged with lying about being in Tsarnaev's dorm room at the University of Massachusetts-Dartmouth when two other friends removed a backpack and other potential evidence several days after the April 2013 attack.
Phillipos attended high school in Cambridge, Massachusetts, with Tsarnaev and later attended college with him.
A defense lawyer had argued that Phillipos, now 21, was a frightened 19-year-old who couldn't remember certain details because he had smoked marijuana for at least 12 hours straight.
Prosecutors say Tsarnaev and his older brother, Tamerlan, planted two pressure-cooker bombs near the Boston Marathon finish line on April 15, 2013.
Three people were killed and more than 260 others were injured. An MIT officer was later killed as he sat in his car. Police say he was also a victim of the Tsarnaev brothers.
Tamerlan Tsarnaev died following a shootout with police several days after the bombings.
Dzhokhar Tsarnaev has pleaded not guilty to 30 federal charges and is scheduled to go on trial in January. He could face the death penalty if convicted.