David Turpin, 56, and Louise Turpin, 49, starved their children to the point that 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 on Thursday.
"The victimisation 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."
The couple were charged with torture, child abuse, dependent adult abuse and false imprisonment. David Turpin was also charged with performing a lewd act on a child under the age of 14.
The litany of abuses was enough to invoke a house of horrors that apparently went unnoticed for years in California and Texas until Sunday, when a 17-year-old girl managed to escape and call the police.
The girl and her siblings had plotted the escape for two years, Mr Hestrin said. Another girl who escaped out a window with the teen turned back out of fear.
Mr Hestrin did not say what finally triggered the girl to act.
When officers arrived at the house on Sunday in Perris, about 60 miles southeast of Los Angeles, they were shocked by what they found.
The children's malnutrition was so severe that it was consistent with muscle wasting and had led to cognitive impairment and nerve damage, Mr Hestrin said. The oldest child, a 29-year-old woman, weighed 82 pounds.
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 two to 29. The torture and false imprisonment charges do not include the two-year-old.
The charges date to 2010, when the couple moved to Riverside County from outside Fort Worth, Texas, where the abuse began, Mr Hestrin said.
The parents have been jailed on 9 million US dollars bail each. They pleaded not guilty on Thursday at their first court appearance. If convicted of all charges, they could be sentenced to life in prison.
David Turpin's father, James, the grandfather to the children, said from his home in Princeton, West Virginia, that he did not believe the reports about the abuse.
"I'm going to talk with the children, find out the real story on this as soon as I can get a call through to them," James Turpin told The Associated Press.
Turpin's father, James, said he was surprised by news of his son's arrest.
James and his wife Betty said that they are considered to be a good Christian family in their community and that added that "God called on them" to have as many children as they did.
The pair also said their grandchildren had "very strict homeschooling," and they would memorise long passages of the Bible, some of them aimed to learn the entire Bible.
The abuse began with the children being tied to beds with ropes and then hog-tied, Mr Hestrin said. When one child was able to wriggle free, the couple began restraining them with chains and padlocks - for up to weeks or months at a time, Mr Hestrin said.
On Sunday, three children had been shackled to beds, though the parents freed two of them when officers knocked on the door, Mr Hestrin said. Officers found a 22-year-old still chained to a bed.
Evidence of human waste on the floor indicated the children were prevented from using the toilet. Sheriff's deputies said the stench in the house was overwhelming.
The children were also beaten and choked, Mr Hestrin said.
The couple may have been able to hide the abuse by schooling their kids at home and functioning in the dark of night. The children were reared on the graveyard shift, with the family staying up all night and going to sleep at 4am, Mr Hestrin said.
While the children were deprived of food, the parents ate well and even taunted the children by letting them see apple and pumpkin pies they weren't allowed to have, Mr Hestrin said.
Similarly, the children were not allowed to play with toys, though they were found throughout the house - in their original packaging.
One of the only things the children were allowed to do was to write in their journals.
Hundreds of journals were found in the home. Mr Hestrin said prosecutors expect the children's writing to provide powerful evidence against the parents.
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