JOLIET, Ill. — A pathologist who performed a second autopsy on Drew Peterson's third wife years after she was found dead in her bathtub says the only plausible explanation for her death is that she was murdered.

Larry Blum described to jurors Thursday how Kathleen Savio had a gash on the back of her head and fresh bruises on her front. He says an accidental fall couldn't have caused injuries on both sides of her body.

Peterson has pleaded not guilty to killing Savio in 2004. Authorities initially ruled her death accidental. Blum performed his autopsy after Peterson's fourth wife, Stacy Peterson, disappeared in 2007. That eventually led to Peterson's arrest.