RIVERSIDE, Calif. -- A California couple tortured a dozen of their children for years, starving them to the point their growth was stunted, chaining them to their beds for months at a time and forbidding them from showering more than once a year or using the toilet, a prosecutor said Thursday.

"The victimization appeared to intensify over time," Riverside County District Attorney Mike Hestrin said in announcing charges. "What started out as neglect became severe, pervasive, prolonged child abuse."

David Turpin, 56, and Louise Turpin, 49, were charged with multiple counts of torture, child abuse, dependent adult abuse and false imprisonment. David Turpin was also charged with performing a lewd act on a child under age 14.

Malnutrition was so severe it was consistent with muscle wasting and had led to cognitive impairment and nerve damage, Hestrin said. The oldest child, a 29-year-old woman, weighed 82 pounds. A 12-year-old was the weight of a typical 7-year-old.

Some of the 13 children had been isolated so long they did not know what a police officer was.

The victims range in age from 2 to 29. The torture and false imprisonment charges do not include the 2-year-old, who was not malnourished.

The parents were jailed on $12 million bail each after pleading not guilty Thursday at their first court appearance. If convicted of all charges, they could be sentenced to life in prison.

The abuse began with the children being tied to beds with ropes and then hog-tied, Hestrin said. When one child was able to wriggle free, the couple began restraining them with chains and padlocks -- for weeks or months at a time, Hestrin said.

Punishments included being beaten and choked, Hestrin said.

The children never received dental care, and they had not seen a doctor in more than four years. When the girl who escaped was asked whether any pills were in the home, she did not understand what medication was.