Bomb `` tore large chunks of flesh out '' of boy 's body , prosecutor says . Defense admits Dzhokhar Tsarnaev 's role in U.S. Marathon bombings . Older brother influenced Tsarnaev to follow him , attorney says .
Bomb `` tore large chunks of flesh out '' of boy 's body , prosecutor says . Defense admits Dzhokhar Tsarnaev 's role in Boston Marathon bombings . Older brother influenced Tsarnaev to follow him , attorney says .