A jury finds Dzhokhar Tsarnaev, surviving brother behind the Boston Marathon bombings, guilty of plotting to use a weapon of mass destruction.
The jury in Boston, Massachusetts, will now decide whether Tsarnaev receives a life sentence or the death penalty.
Three people were killed and more than 260 injured when the bombs exploded at the finish line in April 2013.
His lawyers maintained he played a role in the attacks but said his older brother was the driving force.
The verdict is still being read for other counts.
The decision was reached on Wednesday, after the jury deliberated for just over 12 hours spread over two days.
Tsarnaev, 21, kept his hands folded in front of him and looked down as the guilty verdicts were read.
The conviction was widely expected because his lawyer made the surprise admission during opening statements that he took part in the bombing.
That admission was part of a defence strategy to paint Tsarnaev's elder brother, Tamerlan, as the mastermind of the attack who influenced Tsarnaev into participating.
Prosecutors portrayed them as equal partners in a plan to "punish America" for wars in Muslim countries.
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