Alleged Boston bomber pleads not guilty

Alleged Boston Marathon bomber Dzhokhar Tsarnaev pleaded not guilty Wednesday to committing the worst mass-casualty attack on U.S. soil since 9/11, a crime that could bring him the death penalty.

The 19-year-old ethnic Chechen spoke clearly in court, repeatedly answering that he was "not guilty" of charges that he killed three people April 15 by setting off homemade pressure-cooker bombs, assembled by him and his older brother, Tamerlan, who later fatally shot a university police officer.

That shooting, and a later gun battle with police in the suburb of Watertown, Mass., led to the death of 26-year-old Tamerlan Tsarnaev and a daylong lockdown of most of the Boston area, as police searched for Dzhokhar. He was found, badly wounded, hiding in a boat in a backyard.

The marathon attack injured about 264 people, with many losing their legs.

Tsarnaev's appearance was the first time he has been seen in public since he was arrested on April 19.