A jury has found Justin Stein guilty of murdering schoolgirl Charlise Mutten, whose body was dumped in a barrel by a river outside Sydney.

At the time of the nine-year-old’s death, Stein, 33, was in a relationship with Charlise’s mother, Kallista Mutten, who he maintained was the one that killed the girl.

The jury deliberated for almost two weeks before delivering its verdict on Wednesday, following a four-week trial.

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.

At the time of her death, she had been visiting her mother and Stein from the Gold Coast, where she lived with her grandparents.

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.

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

During Charlise’s visit, the trio spent their time between a property at Mount Wilson, in the Blue Mountains, that was owned by Stein’s mother, and 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 then that prosecutors said he killed the girl.

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.

Crown prosecutor Ken McKay SC 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.

Stein said he went along with a plan to cover up the murder, including lying to police about leaving the girl in the care of a woman who was valuing property at the Mount Wilson estate.

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.