CINDY Palmer has told how she gave her daughter up during a "severe domestic violence situation" because she thought it was the safest option for a then seven-year-old Tiahleigh.

But instead, five years later, Tiahleigh would die at the hands of her foster father after being molested by her 18-year-old foster brother.

A supplied image obtained Sat. Nov. 7, 2015 shows Tiahleigh Palmer, 12, who was last seen outside Marsden State High School, Brisbane on the morning of October 30. Tiahleigh's body was found on the banks of the Pimpama River on the northern Gold Coast.
A supplied image obtained Sat. Nov. 7, 2015 shows Tiahleigh Palmer, 12, who was last seen outside Marsden State High School, Brisbane on the morning of October 30. Tiahleigh's body was found on the banks of the Pimpama River on the northern Gold Coast.

Rick Thorburn pleaded guilty to murder on Friday and will serve 20 years before being eligible for parole. In a "confession" letter, he claimed to have no memory of how he killed his young ward - or the two-and-a-half years that followed.

The court heard Rick killed Tiahleigh on October 29, 2015, because he thought Tiahleigh might be pregnant and he thought his son would go to prison.

"I was suffering through a very severe domestic violence situation," Cindy Palmer told 60 Minutes.

A facebook photograph of Rick Thorburn and family Josh, Julene and Trent. Rick and Trent have been charged in relation to the murder of Tiahleigh Palmer
A facebook photograph of Rick Thorburn and family Josh, Julene and Trent. Rick and Trent have been charged in relation to the murder of Tiahleigh Palmer

"So, I actually went to the department for help because I realised that one day I was just going to die and (she) was just going to be left there by (herself).

"I still firmly believe that the day I went to the department asking for help, I made the right decision. It's not what I wanted and it wasn't the outcome any of us wanted, but at the end of the day I thought it was the safer option."

But life only got worse for Cindy after giving up her daughter, she said.

"At first, I was so devastated at being apart from her that I spiralled out of control, into drugs and homelessness."

Cindy told the program she'd had a bad feeling about the Thorburn family and was worried her daughter would be living with teenage boys.

"Straight away, I said no," she said.

Cindy Palmer mother of Tiahleigh Palmer, murdered by RICK Thorburn — Photo Supplied Channel 9.
Cindy Palmer mother of Tiahleigh Palmer, murdered by RICK Thorburn — Photo Supplied Channel 9.

"The first ever time that I met Rick, the first words that came out of his mouth were about how he was in a gang when he was younger and he was running guns and prostitutes. And he was proud of this."

Family members have told police that Rick was prone to telling elaborate stories to impress people. Cindy said whether or not the story was true, it was "inappropriate".

Police and the Crime and Corruption Commission used various strategies to gather the evidence needed to arrest Rick, his wife Julene and their boys Josh and Trent.

Julene and Josh were jailed for their part in covering up the schoolgirl's murder and Trent was jailed on a charge of incest.

Foster father Rick Thorburn has been charged with the murder of 12 year old school girl Tiahleigh Palmer in 2015. Pictures: Jack Tran
Foster father Rick Thorburn has been charged with the murder of 12 year old school girl Tiahleigh Palmer in 2015. Pictures: Jack Tran

In recorded police interviews, Josh said his father showed no emotion after murdering Tiahleigh.

"He didn't cry. He seemed quite assured and defensive of what he'd done and why he'd done it. Obviously, it was to protect Trent," he said.

Cindy said she had received abuse and even death threats over her decision to put her daughter in foster care.

"I didn't murder my daughter," she said.

"I've worked really hard not to be that person anymore but I guess maybe it is a little bit of guilt because obviously I was meant to be a mother and I should have made better choices."