Any one of three people could have inflicted the fatal blow that killed four-year-old Tyrell Cobb, and there is not enough evidence to hold his mother responsible, a court has heard.
Tyrell's mother Heidi Strbak pleaded guilty and was convicted of manslaughter but is contesting allegations she delivered the fatal blow which killed him.
Strbak's former partner Matthew Scown, who was given a suspended sentence for manslaughter last month, called emergency services when the boy began vomiting and lost consciousness.
Tyrell died in a Gold Coast hospital in May 2009.
Prosecutor Phil McCarthy said Tyrell died from "blunt force trauma" which caused "leakage of the child's stomach contents".
"He would have survived if he had received treatment," he said.
"It was Heidi Strbak who applied the blunt force trauma to her son."
Strbak's defence barrister Greg McGuire said Mr Scown, Strbak and Tyrell's uncle all had contact with the child before his death and there was not enough evidence to hold Strbak responsible for the fatal wound.
He said the court would hear that Scown had previously assaulted Tyrell.
"He kicked Tyrell in the backside after he had urinated on the floor," he told the court.
Mr McGuire said Scown would allege Tyrell had a fall in the shower the day before his death.
The prosecution said residents witnessed Strbak acting abusively towards her son on multiple occasions and heard "sounds of smacking or hitting coming from inside the unit".
"They would also hear Tyrell's screams and cries," Prosecutor Phil McCarthy said.
The court was shown confronting images of Tyrell's bruised body which also had a scar on his ankle, likely from a cigarette lighter.
The contested sentence is due to run for three days.
