A California couple who inflicted years of torture and abuse on 12 of their 13 children have been sentenced to life in prison.

Key points: Several of the children spoke in court during an emotional sentencing hearing

Several of the children spoke in court during an emotional sentencing hearing Both David and Louise Turpin apologised for the abuse they inflicted

Both David and Louise Turpin apologised for the abuse they inflicted The pair will be eligible for parole after serving 25 years in prison

The sentencing of David and Louise Turpin was preceded by the first public statements from some of the children, who alternately spoke of love for their parents and what they had suffered despite it.

The Turpins pleaded guilty in February to neglect and abuse after one of their daughters escaped from their home and called 911 for help.

One of the adult children walked into court already in tears just after the hearing began, holding hands with a prosecutor.

"Life may have been bad but it made me strong. I fought to become the person that I am," one of the daughters, who is now 30 years old, said.

"I saw my dad change my mum. They almost changed me, but I realised what was happening … I'm a fighter, I'm strong and I'm shooting through life like a rocket."

The couple pleaded guilty as part of a deal with prosecutors to serve sentences of 25 years to life in prison. ( Supplied: Riverside County Sheriff's Department )

Some of the others said they still loved their parents. One asked for a lighter sentence because "they believed everything they did was to protect us".

"Although it may not have been the best way of raising us, I am glad that they did because it made me the person I am today," one of the daughters said in a statement.

"I just want to thank them for teaching me about God and faith. I hope that they never lose their faith.

"God looks at the heart and I know he sees theirs. I pray often for them."

The horrors within the home were concealed behind a veneer of suburban normalcy in a middle-class section of Perris, a small city about 100 kilometres south-east of Los Angeles.

David Turpin, 57, had been an engineer for Lockheed Martin and Northrop Grumman. Louise Turpin, 50, was listed as a housewife in a 2011 bankruptcy filing.

The children's desperate plight became public after a teenage daughter jumped from a window and called 911, describing years of horrific abuse to a police dispatcher.

When deputies arrived, they were shocked by what they discovered. A 22-year-old son was chained to a bed and two girls had just been set free from their shackles.

The house was covered in filth and the stench of human waste was overwhelming.

David and Louise Turpin, with their 13 children, in an image posted to Facebook in 2016. ( Facebook: David-Louise Turpin )

Children said they were beaten, caged and shackled to beds if they did not obey their parents.

Most of the 13 children — who ranged in age from 2 to 29 — were severely underweight and hadn't bathed for months.

They were mainly kept in their rooms except for meals, which had been reduced from three to one per day, a combination of lunch and dinner.

27yo son using newfound freedom to learn how to ride a bike

In a statement, one daughter said she thought their mother believed they were eating too much.

"Through the years things became more and more overwhelming but they kept trusting in God," she said.

"I remember our mother sitting in her recliner and crying, saying she don't know what to do. She didn't want to use ropes or chains, but she was afraid her children were taking in too much sugar and caffeine."

The children were not allowed to play like normal children. Other than an occasional family trip to Las Vegas or Disneyland, which one of the daughters mentioned at Friday's hearing, they rarely left the home.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 51 seconds 51 s David and Louise Turpin's lawyer address media after their life sentencing

In a statement made during the sentencing, one son said he only recently learned to ride a bike.

"Since January I have learned so much and become very independent," the 27-year-old said.

"In June of last year I learned how to ride a bike and ever since then I've been hooked and ride it everywhere, such as to school, the store, or sometimes I just go on long rides because I enjoy it so much."

He added he had nightmares of his parents beating or chaining up his siblings, but said he had put it behind him.

"That is the past and this now," he said.

"I love my parents and have forgiven them for a lot of the things they did to us."

Although the couple filed paperwork with state authorities to homeschool their children, learning was limited.

"We don't really do school. I haven't finished first grade," the 17-year-old said, according to police deputy Manuel Campos.

Neighbours said they rarely saw the children outside but were not aware of anything suspicious. ( Reuters: Mike Blake )

Investigators found that the toddler had not been abused, but all of the children were hospitalised after they were discovered.

"I'm sorry for everything I've done to hurt my children. I love my children so much," Louise Turpin said at the sentencing.

David Turpin's lawyer read part of a statement because he was too upset. "My homeschooling and discipline had good intentions," he said. "I'm sorry if I've done anything to cause them harm."

The couple will be eligible for parole after 25 years.

AP