Man Who Left His Wife for Dead at Sheriff's Substation Faces 25 Years to Life

A San Diego man who fatally stabbed his estranged wife to death in a parking lot at the Imperial Beach sheriff's substation earlier is set to be sentenced Friday.

Marvin Dennis Duncan, 60, pleaded guilty in May to first-degree murder and faces a stipulated 25 years to life in prison.

Shortly after 3:30 p.m. Feb. 6, Duncan pressed an intercom button at a side door at the precinct house on Imperial Beach Boulevard, said sheriff's homicide Lt. Glenn Giannantonio. 

When a deputy answered, Duncan, who was holding two toddlers, announced he had just killed his spouse, the lieutenant said.

The victim, Duncan's wife, Rocio, 36, was found lying on the ground on the west side of the substation. She died a short time later.

Duncan was detained for questioning and later arrested. The children, who were unharmed, were taken into protective custody. The motive was under investigation.