Video After The Jump Report via WBUR -- A Massachusetts teenager convicted of fatally stabbing and then decapitating a high school classmate has been sentenced to life in prison. Mathew Borges, 18, of Lawrence, will be eligible for parole in 30 years under the maximum allowable sentence handed down on Tuesday by Superior Court Judge Helene Kanzajian. A jury convicted Borges in May of first-d…