San Diego County District Attorney Summer Stephan announced today that a 19-year-old man who fatally stabbed a 17-year-old male at a house party has been sentenced to 12 years in state prison.

On August 10, 2023, James Mumper Jr. pleaded guilty to voluntary manslaughter and admitted the allegation of personal use of a deadly weapon. Mumper additionally admitted three aggravating factors in the commission of this crime in connection with the stabbing that occurred   at the house party in Chula Vista. 

“We all grieve with the family for the loss of such a young life taken by senseless violence,” DA Stephan said. “We hope the family can find solace in the justice that was delivered through this prosecution.”

This case was prosecuted by Deputy District Attorneys Alexis Lamprea and Garret Wong.