Editor's note: This report includes disturbing descriptions of child abuse.

Updated at 5:30 p.m. ET

Just days after Louise and David Turpin's 13 children were discovered deeply malnourished and — in some cases — shackled to furniture in their home, the Southern California couple have been charged with torture, child abuse and false imprisonment. The two parents face the possibility of life in prison.

"As a prosecutor, there are cases that stick with you, that will haunt you," Riverside County District Attorney Michael Hestrin said at a news conference Thursday. "Sometimes in this business, we're faced with looking at human depravity — and that's what we're looking at here."

The Turpin children, who range in age from 2 to 29, allegedly suffered years of neglect and escalating abuse, both physical and psychological. For at least eight years and in three homes, Hestrin said the children were forced to eat rarely, shower no more than once a year and, when punished, were often beaten, strangled or tied up "for weeks or even months at a time."

"Circumstantial evidence in the house suggests that the victims were often not released from their chains to go to the bathroom," Hestrin added.

Police did not discover the house in Perris, Calif., until Sunday, when the 17-year-old daughter enacted a plan she and her siblings had been working on for more than two years. Hestrin said that the daughter, together with another sibling, escaped through a window — and that though the other sibling soon grew frightened and turned back, the 17-year-old forged ahead and contacted local police.

What they found appalled them.

"To give you an example," Hestrin said Thursday, "one of the children at age 12 is the weight of an average 7-year-old. The 29-year-old female victim weighs 82 pounds. Several of the victims have cognitive impairment and neuropathy — which is nerve damage — as a result of this extreme and prolonged physical abuse."

And though the parents had reportedly registered their home as a private school with the state's Department of Education, the children "lack a basic knowledge of life," Hestrin said. "Many of the children didn't know what a police officer was. The 17-year-old, when asked whether there was medication or pills in the home, didn't know what medication or pills were."

Not long after police visited the home Sunday, the children were taken to medical centers for treatment and the parents were taken into custody.

Among the charges the parents face: 12 counts each of torture, 12 counts each of false imprisonment, seven counts each of abuse of a dependent adult, and six counts each of child abuse or neglect. David Turpin also has been charged with committing a lewd act against a child using force, fear or duress.

As to why the parents face 12 counts and not 13, Hestrin responded: "I don't know why, but apparently the 2-year-old was getting enough to eat."

He noted that officials reserve the right to file more charges as the investigation proceeds.

The parents pleaded not guilty Thursday. Their bail is set at $12 million each.

Prosecutors hope to learn more about the lives of these children from one of the few privileges Hestrin said they were allowed: their journals. Hestrin said they lived in Fort Worth, Texas, until 2010 when they moved to Murrieta, Calif., and finally settled in Perris in 2014. And during this time, despite being kept in separate rooms or chained to furniture, the children were allowed to keep journals of their own.

"We now have recovered those journals — hundreds of them — and we are combing through them for evidence."

For the time being, authorities' knowledge of the situation derives mostly from the children's accounts: Stories of the parents eating well and leaving food in front of their children, who were forbidden to touch it. Stories of toys scattered about the house but never removed from their original packaging. Stories of a ban on washing above the wrist while washing their hands, which if violated, would elicit accusations that they "were playing in the water."

"This is severe emotional and physical abuse," Hestrin said Thursday. "There's no way around that. This is depraved conduct."

Hestrin said the family would wake around nightfall and head to bed in the early morning, around 4 or 5 a.m. It was shortly after this morning curfew, around 6 a.m., that the 17-year-old daughter placed the 911 call that brought police to her family's home.

For now, and likely for some time to come, she and her siblings are receiving medical and psychological treatment.

"They've gone through a very traumatic ordeal. I can tell you that they're very friendly. They're very cooperative," Mark Uffer, CEO of the Corona Regional Medical Center, where the adults have been hospitalized, said at a news conference Tuesday.

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