An autopsy revealed the little boy had suffered severe blunt force trauma to the back and front of his head, causing multiple subdural haemorrhages as well as the brain swelling that ultimately resulted in his death.
But when police first interviewed the boy's male guardian - Kodi James Maybir - the man said the seven-year-old had simply fallen off his pogo stick.
And he now claims the boy's fatal injuries were caused when a wrestling move went wrong.
"He's always on that pogo stick," Mr Maybir allegedly told police on May 21, 2013, after the boy's body had been taken away.
"He just fell off ... hit the back of his head. We kept an eye on him all day, he mainly just lay in the bed."
But prosecutors and police say this was a lie concocted by Mr Maybir - a Christian pop music producer - to hide the fact that he had taken the boy's life.
Mr Maybir has been charged with murdering the child at the Oatley music studio where the boy lived with his siblings and his mother, Kayla James, with whom the accused was in a relationship.
The death allegedly followed months of violent abuse, and Mr Maybir has been charged with 13 additional offences in relation to this abuse. He has pleaded guilty to six of them.
However, he has pleaded not guilty to murder.
James was convicted of manslaughter and has been sentenced.
Crown prosecutor Chris Maxwell, QC, told the jury on Thursday that the pogo stick explanation was the first of three separate reasons given by Mr Maybir during the course of his interviews with police after the boy's death.
In his second interview, the accused allegedly said that the boy had fallen after being forced to stand on a large coffee tin that was balancing on a metal microphone box as part of a "bootcamp" style punishment.
Then, some months later, Mr Maybir claimed that the boy had fallen twice, which explained the injuries to different parts of his head.
On Thursday, Mr Maybir's barrister, Grant Brady, said that, in fact, the injuries had been caused by a "terrible accident" while his client and the boy were wrestling.
"The deceased and Mr Maybir both loved wrestling," Mr Brady said.
"One of the things that Mr Maybir liked to do was pick [the child] up and throw him on to the couch or a bed.
"That morning that was exactly what he was doing. He picked him up and threw him on to the couch. But [the boy] grabbed him by the shirt and, rather than hitting the couch, he hit the floor."
Mr Maxwell said the trial would hear evidence from forensic experts that none of the explanations Mr Maybir gave to police was consistent with the nature of the injuries.
"The forensic paediatrician will say that this explanation of one or two falls doesn't explain the severity of the injuries," Mr Maxwell said.
"He had multiple different impact injuries to different sides of his head."
The court heard that the autopsy conducted after the boy's death found dozens of other injuries consistent with abuse in the weeks and months prior to his death.
"Further X-rays identified rib fractures ... five or six weeks old to the front left of his chest," Mr Maxwell said.
There were also fractures to the boy's foot, his little finger, as well as bruises and abrasions to his entire body.
Mr Brady said that some of the things his client had done were "absolutely shameful".
He said Mr Maybir admitted that he should have sought medical attention for the boy immediately after the "accident" and so he was guilty of manslaughter by criminal negligence.
But he said the accused was not guilty of murder because he had not intended to kill the boy nor cause him serious injury.
Mr Brady also said that, soon after his client had met James, he had become "deeply infatuated" with her and agreed to let her and her children move in with him at the music studio because he believed that she had become estranged from her family and had nowhere else to go.
He had been "entirely unsuited" to caring for children and had developed what he now accepted was a "completely inappropriate" method of disciplining them, drawn from a number of exercise bootcamps he had led, movies and television programs including Super Nanny and Survivor.
The trial continues.
