A San Antonio man has been sentenced to 75 years in prison over the 2004 killing of his girlfriend's four-year-old son.

Twenty-two-year-old Paul Castellano was arrested one day after Joshua Pacheco died of what doctors say was strangulation and trauma to the abdomen.

The man had denied killing the boy -- saying the youngster choked on some food.

The Bexar County jury convicted Castellano of murder.

Investigators say the boy suffered the fatal injuries while his mother was at work.