When a 17-year-old girl jumped out a window from the house where her parents allegedly starved and tortured their 13 children, she broke a silence that had likely lasted years.

It's not clear why the teenager waited so long to act, but psychiatrists say such behaviour is not uncommon even in cases of extreme deprivation.

Most people would recognise milder forms of the same inaction that is a coping mechanism, whether it's failing to speak out against off-colour jokes, enduring sexual harassment or staying in an awful marriage, said Dr Bruce Perry.

“This happens all the time. The number of individuals who would immediately respond to an opportunity where they could get away is very small compared to the number of people who would have that paralysis and insecurity and confusion about what to do,” said Perry, a psychiatrist and senior fellow at The ChildTrauma Academy in Houston.

The vulnerable girl might have been shamed, beaten or threatened with violence and only after many missed opportunities did she probably work up the courage to act, Perry said.

“It's pretty remarkable that she'd do that,” he said. “The power that must have been exerted to keep an entire family like that for so long must have been pretty sophisticated.”

David Turpin, 56, and his wife, Louise Turpin, 49, were arrested on Sunday after authorities found the malnourished children in their home in suburban Perris, 60 miles southeast of Los Angeles. They were jailed on $9 million bail each and are expected to appear Thursday in Riverside County Superior Court on charges that could include torture and child endangerment, authorities said.

Investigators at the home on Wednesday removed dozens of boxes, what appeared to be two safes and pieces of a bed frame.

Some siblings were shackled to furniture in the foul-smelling four-bedroom home that looked perfectly normal from the outside.

The couples' children - ages two to 29 - were so emaciated the older ones still looked like children. Authorities thought the 17-year-old daughter who called 911 was only 10 when they found her.

Until the girl fled with photographic evidence, it appears no one, neither neighbours nor public officials, knew anything about what was happening inside.

The Turpins have lived in two Riverside County communities since moving to California in 2011, and police said they were never called to either home, nor were any reports fielded by child protective services.

In Hill County, Texas, where they lived previously, the sheriff's office received a call from a neighbour complaining that a pig belonging to the Turpins escaped from a pen and ate 55 pounds of his dog food.

In another report, David Turpin said that the family's dog had bitten their four-year-old daughter on the face. He told police he took the girl to a hospital for stitches and the dog to a veterinarian to be put down, according to records obtained by the Associated Press.

It's not clear what motivated the Turpins to live a secluded life with their large brood or what went on in the house. Parents convicted in similar cases exerted control over their children though intimidation, psychological and physical coercion, and frequently possessed their own belief system.

“They develop a kind of cultish doomsday type of religion where the father becomes this mythical leader and the mother and children's duty is to serve the father,” attorney Ambrosio Rodriguez said.

Rodriguez was a longtime Riverside County prosecutor who sent Jessica Banks, a pastor and mother, to prison for life for beating, starving and drugging her five adopted daughters, who were kept locked in her garage.

The Turpin children appeared to be cut off from the outside world, despite taking trips to Disneyland and Las Vegas, where the parents renewed wedding vows in a service presided over by an Elvis impersonator.

“They weren't allowed to watch TV. They weren't allowed to have friends over - the normal things that kids do,” the children's aunt, Teresa Robinette, told NBC's Today show.

Individuals held under such conditions often become so physically and emotionally weak “that they are unable to free themselves, even if an opportunity arises,” said Dr Allen Keller, who runs the Bellevue-NYU Center for Survivors of Torture in New York. “The abuser has basically taken complete control of them. It is a state of severe helplessness.”

Many victims of abuse suffer from severe depression, anxiety, nightmares and are easily startled in public.

The children were educated in the home. No state agency regulates or oversees private schools in California, but they are subject to an annual inspection by the state or local fire marshal.

The city could find no records of fire inspections, Perris Assistant City Clerk Judy Haughney said in response to a public records request by AP. City Fire Marshal Dave Martinez did not return repeated phone messages seeking comment.

Home schooling can further isolate children, denying them social interactions with peers who aren't their siblings and also giving the parents the ability to teach whatever they want.

Turpin family: 13 siblings who were held captive by their parents Show all 15 1 /15 Turpin family: 13 siblings who were held captive by their parents Turpin family: 13 siblings who were held captive by their parents David and Louise Turpin with their 13 children who were being held captive by their parents in the family home in Perris, California. Facebook Turpin family: 13 siblings who were held captive by their parents Riverside County District Attorney Mike Hestrin speaks during a press conference announcing charges against David Turpin and Louise Turpin in relation to their 13 malnourished children found chained in their home, in Riverside. The two parents were charged with multiple counts of Child abuse, torture, abuse of dependent adults and false imprisonment and could face close to 100 years to life in prison if convicted. EPA Turpin family: 13 siblings who were held captive by their parents The home of David Allen and Louise Anna Turpin, where some of their children were bound with chains and padlocks. Reuters Turpin family: 13 siblings who were held captive by their parents David Allen Turpin poses for a mugshot after being arrested. Riverside County Sheriffs Department via Getty Turpin family: 13 siblings who were held captive by their parents One of the captives, a 17-year-old girl, escaped over the weekend and notified the Riverside Sheriff’s Department. Facebook/David-Louise Turpin Turpin family: 13 siblings who were held captive by their parents Perris residents watch as media gather in front of Turpin family home. The Sheriff's deparmtent said "the parents were unable to immediately provide a logical reason why their children were restrained in that manner." AFP/Getty Turpin family: 13 siblings who were held captive by their parents The children were found in dark and foul-smelling surroundings and "The victims appeared to be malnourished and very dirty,” the department said. Facebook/David-Louise Turpin Turpin family: 13 siblings who were held captive by their parents Neighbours stand outside the home. Getty Turpin family: 13 siblings who were held captive by their parents Louise Anna Turpin poses for a mugshot after being arrested. Not all of their victims were children: of the 13 victims, seven were between the age of 18 and 29, according to the Sheriff's Department. Riverside County Sheriffs Department via Getty Turpin family: 13 siblings who were held captive by their parents David and Louise Turpin in 2015. Authorities arrested them on torture and child endangerment charges, setting bail at $9m (£6.5m) apiece. Facebook/David-Louise Turpin Turpin family: 13 siblings who were held captive by their parents David Turpin and Louise Turpin appear in court for their arraignment in Riverside Reuters Turpin family: 13 siblings who were held captive by their parents David Allen Turpin and his wife, Louise Anna Turpin celebrate a renewal of their wedding vows with Elvis impersonator Kent Ripley in Las Vegas in 2011 A Elvis Chapel via AP Turpin family: 13 siblings who were held captive by their parents David Allen Turpin appears in court for his arraignment in Riverside. Prosecutors filed 12 counts of torture, seven counts of dependent adult abuse, six counts of child abuse and 12 counts of false imprisonment against Turpin and his wife, Louise Anna Turpin. The Press-Enterprise via AP Turpin family: 13 siblings who were held captive by their parents Neighbour Liza Tozier, and her son, Avery Sanchez, 6, drop off his large "Teddy" as a gift for the children. AP Turpin family: 13 siblings who were held captive by their parents Louise Turpin appears in court for her arraignment in Riverside. Authorities say the abuse left the children malnourished, undersized and with cognitive impairments. Reuters

Perry, who led a team of therapists that interviewed most of the surviving children from the Branch Davidian cult in Waco, Texas, said that one five-year-old could recite whole books of the Bible but could not identify circles and squares.

Other groups have succeeded in keeping their behaviour secret by enlisting older children in the rearing and indoctrinating of the younger ones. If older siblings participated in the abuse, they would be less likely to call police.

“I've seen this movie before,” Rodriguez said. “It's going to get more creepy and make our skin crawl. And at the end of it, we're all going to be asking the same question: 'How did this happen in front of us and no one noticed?”'