'It is all taken care of': Words of evil from Tiahleigh's killer

That is what Rick Thorburn told his wife and sons on October 29, 2015.

One week later, the decomposed and mostly naked body of his 12-year-old foster daughter, Tiahleigh Palmer, was found partially submerged on the banks of the Pimpama River.

Thorburn, his wife Julene and two sons Trent and Josh continued to live their normal lives while maintaining a previously hatched story that Tiahleigh had been dropped off at school on the morning of October 30 prior to her disappearance.

Thorburn helped carry Tiahleigh’s coffin, in front of about 600 people, at her November 14 funeral.

It was an anonymous tip-off to Crime Stoppers on May 10, 2016, that prompted police to focus on the Thorburn household.

The caller revealed details of a “family meeting”, held the day before a social worker noted Tiahleigh was absent from Marsden State High School, where it had been revealed Trent Thorburn had had sex with his 12-year-old foster sister.

There were fears Tiahleigh was pregnant, with those concerns heightened by the school girl’s complaints of stomach cramps on the evening of October 29.

It has now been revealed by prosecutor Carl Heaton, QC, that after 10pm on the evening of the 29th, Thorburn told his wife and two sons: “Tia is no longer with us, I hope you understand what that means.”

“I have her hidden and I’m going to get rid of her tomorrow night," he told his family.

“I’m going to leave home tomorrow morning as if I’m dropping Tia off to school and then collect some car parts.

“Tomorrow night, I don’t want you boys home, so that I can get rid of Tia’s body. I know a good place where I can get rid of the body.”

On the evening of October 30, Thorburn returned to the family’s Chambers Flat home covered in dirt.

“It’s done,” he said.

When Tiahleigh’s body was found, she was wearing only a pair of ripped black underpants.

Her body was so badly decomposed the cause of death was unable to be determined. The only injury noted was a bruise on her scalp.

The time of her death was established by the rate of absorption in her body of some Nurofen she had taken for the stomach cramps.

The Crime Stoppers call prompted a Crime and Corruption Commission hearing during which all four members of the Thorburn family stuck to the story, but it prompted police to install listening devices in their home.

These devices captured conversations between the family members, including Thorburn telling his wife and sons to “stick to the story” about him dropping Tiahleigh at school and to keep Trent’s relationship with Tiahleigh “quiet”.

All four members of the Thorburn family were arrested in September 2016.

In the Brisbane Supreme Court on Friday, Rick Thorburn pleaded guilty to Tiahleigh's murder, as well as one count of interfering with a corpse, one count attempting to pervert justice and two counts of perjury.

In the packed courtroom, Thorburn, who was wearing long dark pants and a light-blue button-up shirt, wiped tears from his eyes while pleading guilty.

Tiahleigh’s mother, Cindy Palmer, along with several other family members and supporters, were present but were silent when Thorburn pleaded guilty to the charges and remained quiet when Justice David Boddice sentenced Thorburn to life behind bars.

Judge Boddice described Thorburn’s act or murder as cold, calculating and callous.

Outside the court, Ms Palmer said the day marked the end of a long and painful fight for justice for Tiahleigh.

“As her mother, no sentence will ever be enough,” she said.

“Tiahleigh was a beautiful young girl who had her entire life to look forward to.”

“Rick Thorburn took that away from me, from our family and most importantly Tiahleigh.”

Thorburn's wife and two sons have also been jailed.

Trent Thorburn, who admitted to having sex with Tiahleigh, his foster sister, was jailed for a maximum of four years in September 2017 after pleading guilty to four charges, including incest.

His older brother, Joshua Thorburn, was sentenced to three months in July 2017 after pleading guilty to perjury and attempting to pervert the course of justice.

Rick's wife, Julene Thorburn, served six months in jail after pleading guilty on November 2017 to perjury and attempting to pervert the course of justice.

After Thorburn's sentencing, Child Safety Minister Di Farmer said the Queensland government had commissioned three independent reviews, which made more than 100 recommendations to improve the system.

All were accepted by the government, but on Friday afternoon Ms Farmer was unable to say how many of the recommendations had been implemented.

"The important thing to know is that none of those recommendations could have brought back Tiahleigh Palmer, could have actually helped us to predict that Rick Thorburn was capable of what he did to that beautiful young girl," she said.

"We cannot predict human beings like Rick Thorburn and the depth of depravity that he has displayed.

"Every single process that needed to be gone through in assessing Rick Thorburn as a foster carer was gone through, every single box was ticked."

Ms Farmer said the systems in place when Tiahleigh were murdered were "strong and robust".

"And the independent reviews confirmed that those systems were strong and robust," she said.

"The recommendations that have been made are about making sure that we are tightening up the system as much as possible, to make sure that nothing, nobody falls through the cracks."

Ms Farmer said Thorburn had committed an "act of utter betrayal of a beautiful young girl who was entrusted to his care".

"As a mum, as a human being, I was sick to the stomach to hear what had happened to Tiahleigh Palmer," she said.

As was an entire state.

- with Felicity Caldwell