Carpenter is convicted of killing Moureen Gathua, 24, and their 6-month-old son Kyan Gathua-Carpenter in June of that year.
At the time, Carpenter was a U.S. Marine based at Camp Pendleton.
Video: Kwame Carpenter arrested in June 2015 in deaths of his wife, infant son
Investigators said after an argument with his girlfriend, he stabbed her and their son with a kitchen knife and then fled the scene.
He was found and arrested the next day following a short police chase.
