Transcript for Horrific details emerge in case of 13 captive siblings
possible life in prison. Our senior national correspondent Matt Gutman has been tracking the case for us and joins us from that house in Perris, California. Good morning, Matt. Reporter: Hey, good morning, robin. The D.A. In an interview told me that the abuse suffered in that house was, quote, off the charts sadistic. David and Louise turpin are accused not only of beating their children, chaining them to bed, sometimes for months at a time but also systemically starving their children and taunting them. Sometimes they would buy things like apple pie, pumpkin pie, put it on the counter, let the kids smell it but never eat it. There were toys in that house that were unwrapped and now those two parents face up to 75 total counts and if convicted up to life in prison. The police say the parents who routinely chained their children in shackles themselves. The state of California versus Louise Ann turpin and David Allen turpin. Reporter: It spanned decades. If convicted they could face life in prison. District attorney Mike hestrom details the abuse including starving their children and then taunting them with delicacies. They would buy food including pies, apple pies, leave it on the counter, let the children look at it but not eat it. Reporter: Instead they were a steady diet of cruelty. This shows one of their Texas' homes years ago, grime smeared on the stairwells. Human filth on the floors and the children were allowed to bathe only once a year and none of the victims had ever seen a dentist. And the punishments for infractions like washing their hands above the wrists progressively got worse. First with ropes, one victim at one point was tied up and hog tied and then when that victim was able to escape the ropes, these defendants eventually began using chains and padlocks to chain up the victims to their beds. Reporter: The one thing the children were allowed were journals. A surprising hole in the turpins' house of Depp practi-- Depp practice Vegas. That will beowerful evidence of what was happening from the victims. Your understanding they were able to document what was happening in their journals, almost like a realtime basis. That's my assumption and I do believe that that's going to be the case, yes. Reporter: Doctors are now treating the sibling, one of whom is 29 years old and weighs just 82 pounds. That medical staff also acting as their guardians and they're hopeful for their future. We've limited the type of physicians that go in to see them. We've used people that we knew that they could develop a bond with and trust and we feel we've done the best for them while they're here. Reporter: Now one of the things that give investigators and doctors hope is the courage and grit displayed by that 17-year-old girl who managed to escape. Apparently she had been plotting this for over two years. She went out there with a sibling. That sib belong got so afraid she turned back but that 17-year-old pushed forward, managed to contact authorities and they say possibly save her siblings. Robin. Okay, Matt, just can't stop thinking about all those children. We'll bring in our chief legal analyst Dan Abrams in the studio with us and Callahan Walsh who is a child advocate from the national center for missing & exploited children joins us as well. Dan, let me start with you. We just heard in Matt's piece about those journals. That's going to be powerful. And it's going to be really important evidence because they're documents day by day who is apparently happening to them and, look, keep in mind this is occurring over a period of years. So I wouldn't be surprised if as they continue to investigate this, as they continue to go through the journals and as they continue to find out more about this family they could end up adding additional charges beyond the 75 that Matt has talked about here but it's rare to have that kind of realtime documentation of alleged crimes and makes you wonder what is the defense going to be? I don't know. Are they going to claim some sort of religious freedom defense. I don't know but when you have that evidence it's hard to defend. Homeschooling has been brought up. All you need is a simple registration in California. In some states less than that. A lot are talking about what needs to be done now. Homeschooling isn't the problem. The problem is that in a disproportionate number of cases where you have horrible abuse, the kids were homeschooled so what does that mean. Doesn't mean you need to end homeschooling but you need to have some sort of regulation and checking in. It's at school where people are able to determine if something happens to a child and that's the issue. Callahan, let's talk about those precious children and as we heard in the report, the 17-year-old who was so brave and had been planning this for so long and had a sibling and the sibling turned back but thankfully the other went forward, explain the psychology behind this. The bravery she displayed is amazing. You know, this case reminds so much of the Cleveland girls, Michelle knight and Gina Dejesus. They were kidnapped and held guns their will. These kids were brought up from day one. She needed to do something and I know they had little knowledge of the outside world and didn't know what a police officer was so for her to be able to understand something was wrong and to break out of that situation, not only did she save her own live but the life of her 12 other siblings as well. Callahan, as you were talking and showing video of the family with -- out in public and we've seen them on vacation and you know what some people feel when they see pictures like this, well, why didn't the children do something at that point? But please explain again why that is so difficult for them. Right, again, we've seen this in other cases like Elizabeth smart when she was abducted she was seen out in public as well but these abductors in this case unfortunately these kids' parents are using a control-bayed and fear-based control system and with that, these kids think that their parents are the ultimate authority that there's no one else out there that can save them and are fearing the parents so this fear-based control is what kept these kids locked in that house for so long. They did have opportunities outside to get away, but we saw the parents control. They would dress them all in the same outfits and line them up in lines whenever they were going anywhere and stand at the front and back of the lines and make sure they were completely watched at all times. Callahan, as always we appreciate your insight and, Dan, thank you. Hard to talk about in it really is. Brand-new details and interviews and can you see it on a special hour of "20/20" tonight.
This transcript has been automatically generated and may not be 100% accurate.