In December 2021, Charlise Mutten went on her last holiday. Her stepfather is now serving life in prison.

Justin Stein has been jailed for life without parole for the murder of nine-year-old Charlise Mutten.

Charlise's body was found dumped in a barrel by a river just outside of Sydney in 2022.

At the time of the nine-year-old's death, Stein was in a relationship with Charlise's mother, Kallista Mutten, who he maintained was the one that killed Charlise. He claimed he witnessed his then-partner shoot the girl.

The 33-year-old was sentenced in the NSW Supreme Court on Monday to the maximum sentence of life imprisonment.

In handing down the sentence, Justice Helen Wilson said Stein likely shot the girl once in the back while she was trying to flee, before approaching her and firing another shot directly into her head.

"This was a shockingly callous crime," Ms Wilson said.

"The offender approached Charlise and discharged the second shot at close range. It was not survivable and was not intended to be."

Watch: The case of Charlise Mutten. Post continues below. 

Justice Wilson said during the trial she had witnessed Stein pretending to cry as he gave a "wholly false account" of Charlise's death.

"His voice began to shake and then to break, he reached for a tissue and dabbed at his eyes," the judge said.

"I could see very clearly that despite the offender's presentation of distress, he was completely dry-eyed and did not shed a single tear."

Crown prosecutor Ken McKay SC told the court during a sentencing hearing on Friday that due to the extreme nature of the crime, the only appropriate sentence for Stein was life in prison.

"He went to great lengths to avoid being held responsible for his actions," Mr McKay said.

Stein was found guilty of the murder of the nine-year-old back in June. The jury deliberated for almost two weeks before delivering its verdict, following a four-week trial.

In December 2021, Charlise Mutten went on her last holiday.

At the time, she had been visiting her mother and Stein from the Gold Coast, where she lived with her grandparents. She was only visiting Ms Mutten and Stein for a few weeks over the school holidays.  

Charlise's body was found near the Colo River, northwest of Sydney, on January 18, 2022, with gunshot wounds to her face and lower back.

During Charlise's visit, the trio spent the majority of their time at a property at Mount Wilson, in the Blue Mountains. They were staying at the Wildenstein Private Gardens in Mount Wilson — a fancy wedding venue owned by the Stein family.

They also stayed at a caravan at the Riviera Ski Park, about a 90-minute drive away.

Charlise spent the night of January 11 alone with Stein at Mount Wilson, while her mother remained at the caravan.

It is on the evening of January 11 or the morning of January 12 that Stein is believed to have murdered Charlise. 

Stein admitted dumping Charlise's body, but said Ms Mutten shot her daughter and placed her body in a barrel on the back of his ute without his knowledge. 

Stein said he went along with a plan to cover up the murder. He claimed he was unaware Charlise's body was in a barrel on the back of his ute until the next day and that he panicked and ultimately disposed of her remains when he found out.

Ms Mutten denied having any involvement in her daughter's death and broke down in tears when faced with the accusation in court.

Toxicology revealed Charlise had traces in her body of the anti-psychotic drug Seroquel, for which Stein had a prescription to treat schizophrenia. The jury heard an adult dose of the drug would have a profound sedating effect on a child.

The crown prosecutor told jurors it was open for them to find Stein killed Charlise when she became sick after he gave her the drug, which he denied doing.

In the days after Charlise's disappearance, hundreds of police and emergency services searched for her. Dogs, helicopters, SES volunteers and locals all spent five days combing the dense Blue Mountains bushland.

Stein was interviewed as part of those investigations, and he claimed at the time to have also told his partner that her daughter may have been taken by people involved with his criminal past. 

On January 12 — the day Charlise was either murdered, or the day after she was murdered — Stein collected Ms Mutten from the caravan park before they travelled into Sydney and bought $50 of marijuana and $100 of methylamphetamine, also known as ice.

Stein had told Ms Mutten that a woman had arrived at his family's Mount Wilson house to value the property, leaving Charlise in her care.

Stein and Ms Mutten had both previously spent time in prison, in fact, they met while behind bars. He was inside for drug-related offending and she was serving a sentence for dangerous driving causing death. They were both released in 2020.

About an hour from the Mount Wilson property, police found a barrel on the banks of the Colo River. Charlise's body was inside. She had been shot once in the head and once in the lower back. Police also found 99kg of sand that had been used to try and weigh down the barrel.

While searching for Charlise, police had also been retracing Stein's movements. He had bought sandbags, refuelled his boat, and visited the Colo River in the days before the little girl was reported missing. They have CCTV footage of Stein at a BP petrol station towing a boat, in the back of which, is allegedly the barrel containing Charlise's body. 

He was charged with murder the same day they found her. 

During the trial, the prosecution said phone records showed Ms Mutten acted in a way consistent with the belief that her daughter was missing, including messages to Stein urging him to find her.

With AAP.

Feature Image: NSW Police.