Stein was found guilty of murder in June, despite claiming that it was the girl's mother, Kallista Mutten – with whom he was in a relationship – who shot the nine-year-old.
Justice Helen Wilson is due to deliver her verdict in the New South Wales Supreme Court on Monday, saying the girl's young age and the brutal nature of her death were important factors to consider.
Police found Charlise's body near the Colo River northwest of Sydney on January 18, 2022. She had gunshot wounds to her face and lower back.
A community mourned the death of nine-year-old Charlise Mutten, whose body was found in a barrel in a river. (Regi Varghese/AAP PHOTOS)
Judge Wilson said it was possible that Stein shot the girl as she tried to escape before walking toward her and firing another shot directly into her head.
“It's almost like an execution,” she said during the sentencing hearing on Friday.
Prosecutor Ken McKay SC said given the seriousness of the crime, life imprisonment was the only appropriate sentence.
“He has gone to great lengths to avoid being held accountable for his actions,” McKay said.
Stein's lawyer Carolyn Davenport SC said it would be a “very cruel and unusual punishment” to send a man of Stein's age to prison for the rest of his life.
“There was no known motive,” she said.
Charlise had visited her mother and Stein for Christmas from the Gold Coast, where she lived with her grandparents.
She spent the night of January 11 alone with Stein on a property in the Blue Mountains while her mother stayed in a caravan about 90 minutes' drive away.
Charlise's mother Kallista Mutten was in a relationship with the murderer Stein. (Bianca De Marchi/AAP PHOTOS)
In a statement to the court, Ms Mutten said she had unwittingly put her daughter in danger by trusting Stein.
“She trusted my judgment and I hate myself for being so wrong,” she said.
The same day Charlise's body was found, investigators arrested Stein and charged him with murder after using his phone's location data to determine where the barrel had been dropped.
He later admitted to disposing of the body, but claimed he panicked when he discovered it in the bed of his pickup truck.
