Justin Stein's motive to shoot Charlise Mutten dead was to cover for drugging the schoolgirl with a powerful sedative, jurors have heard as his trial draws to a close.
Stein, 33, has pleaded not guilty to murdering the nine-year-old in January 2022, claiming it was the girl's mother, Kallista Mutten, who shot her.
Charlise's body was found dumped by the Colo River, northwest of Sydney, four days after she was reported missing, with gunshot wounds to her head and lower back.
Crown prosecutor Ken McKay SC invited the jury to find Stein had drugged and fatally shot Charlise, describing his version of what happened to the schoolgirl as "nonsense".
Toxicology results revealed Charlise had traces of the drug Seroquel, for which Stein had a prescription to treat schizophrenia, in her system.
An adult dose of the drug would have a profound sedating effect on a child, the court was previously told.
Mr McKay suggested Stein could have become concerned when Charlise became ill after he gave her the drug, leading him to shoot her.
Charlise had been visiting her mother and Stein, who were in a relationship at the time, over Christmas.
The group spent their time between a Mount Wilson property owned by Stein's mother and a caravan at the Riviera Ski Park, about a 90-minute drive away.
Prosecutors allege Charlise spent the night alone with Stein at the Mount Wilson property on January 11 and he killed her either that evening or the next day.
To convict Stein, the jury must be satisfied there was no reasonable possibility that Ms Mutten shot her own daughter, Mr McKay said.
Defence barrister Carolyn Davenport SC began her closing address on Wednesday by reminding the jury of Ms Mutten's history of drug use and mental illness.
Ms Davenport suggested at the time, due to problems in their relationship, she was feeling rejected by Stein.
"She was really hypersensitive to personal conflict," Ms Davenport told the court.
"In order - who knows - to gain attention, to win Justin Stein back, she killed her child."
Ms Mutten told the court during her evidence that Stein had explained Charlise's absence on January 12 by saying he left the girl in the care of a woman who was valuing property at the Mount Wilson estate.
According to Ms Mutten's evidence, she and Stein travelled to Sydney that day to purchase drugs, before returning to Mount Wilson that evening to find the house empty.
Ms Davenport said it was highly unlikely Ms Mutten would have left her sick daughter alone with a stranger.
"Even though Kallista Mutten was never going to win the mother of the year award, it is just not likely that she would have left that child in that house," she said.
During his evidence on Monday, Stein agreed he spent the night of January 11 at the property with Charlise but said the girl was alive the next day.
According to Stein, Charlise travelled with him to pick Ms Mutten up from the caravan before all three went to Sydney.
He said they returned together to Mount Wilson in the evening, soon after which Ms Mutten killed her daughter.
Phone records show Stein called his mother at 8.59pm on January 12 and spoke to her for several minutes, which both Stein and his mother agree occurred.
It is also not in dispute that Ms Mutten searched for hospitals in the area on her phone about 9.21pm and later placed calls to Lithgow and Blue Mountains hospitals.
In the short period between those two events, Stein said Ms Mutten shot her daughter and moved the body.
"It's just a nonsense that version," Mr McKay told the jury.
"Matter for you, but it just did not happen that way."
The jury is expected to begin deliberations from Thursday.
