A friend of Boston bombing suspect Dzhokhar Tsarnaev on Wednesday entered a not guilty plea to charges of heroin trafficking and illegal gun possession. Authorities believe Stephen Silva of Cambridge, Massachusetts, supplied Tsarnaev and his brother, Tamerlan, with the handgun used to kill MIT police officer Sean Collier during the manhunt following the April 2013 bombing. An indictment also alleges Silva conspired to distribute heroin. He waived the right to a bail hearing Wednesday and remains in custody.
