High school cheerleader Emma Walker was killed by a shotgun blast in her home two years ago -- on November 22, 2016 -- by ex-boyfriend William Riley Gaul. The 19-year-old Gaul, who played on the Maryville College football team, was sentenced in September to spend the rest of his life in prison after a Tennessee jury convicted him of first-degree murder. Nancy Grace explores the case with an expert panel including Southern California prosecutor Wendy Patrick,  lawyer & psychologist Dr. Brian Russell, forensics expert Karen Smith, and reporter Pamela Furr.