JERSEYVILLE, Ill.  — An Illinois father and stepmother will spend decades in prison in the starvation death of their 6-year-old son, who authorities say weighed just 17 pounds (8 kilograms) when he died.

The Alton Telegraph reports a judge on Wednesday sentenced Michael L. Roberts to 25 years in prison and Georgena L. Roberts to 20 years.

The 43-year-olds from Jerseyville both pleaded guilty to first-degree murder in November. Two counts of endangering the life and health of a child were dropped.

Authorities have said the couple starved the boy as a form of punishment and withheld food and nourishment on a regular basis. When he died, the boy weighed about a third of the typical weight of a 6-year-old. A preliminary autopsy indicated he died of extreme malnourishment.