A pathologist who performed a post-mortem on Auckland toddler says a fall from a bed does not explain the boy's severe injuries.
Joel Loffley is accused of killing two-year-old James Lawrence, known as JJ, at his home in the suburb of Orakei in November last year.
The Crown says that the boy suffered blunt force trauma to his stomach, severely damaging his internal organs. Mr Loffley, 29, was the partner of the boy's mother and denies the charge.
On Wednesday, the jury at the Auckland High Court watched the videotaped interview police conducted with the accused on the day of the boy's death.
Mr Loffley told Detective Aleki Maka that he and JJ had been playing as he made the bed, but as he pulled the blankets the child fell. He said the boy's breathing was laboured and wheezy for about two minutes but he was alright after being showered and put to bed.
The accused told Mr Maka that he then left JJ in the care of his mother Josephine Lawrence and came home about an hour later. He said he asked Ms Lawrence if she had checked on the boy, but was told she hadn't.
Mr Loffley said he found the boy gurgling with brown liquid dripping from his mouth and he started screaming: "This boy's not boy's not breathing, this boy's not boy's not breathing".
But pathologist Fintan Garavan, who carried out the post-mortem, told the court on Wednesday there was no way that a fall from the bed could have caused the injuries.
Dr Garavan said the force of the trauma was so severe that it split the boy's liver and pancreas in two.
Dr Garavan used a hammer and anvil analogy, saying if the force that struck JJ was the hammer his spine was the anvil, trapping the organs between the two.
The blood loss would have been catastrophic and the child would have died in minutes, he said.
Accused assaulted ex-partners
In the interview with police, Joel Loffley told police that he had convictions for assaulting previous girlfriends.
Mr Loffley told Detective Aleki Maka that he was still on probation for a previous conviction for assaulting his former girlfriend, but said there was no violence in the home towards the child.
"Never assaulted kids. I've got a few from assaulting my kids' mums, but never my kids."
Mr Maka also questioned Joel Loffley about JJ's previous injuries which brought him to the attention of Child, Youth and Family.
Mr Loffley said in the police interview he was aware that the boy broke his arm in September last year, but did not know about an earlier broken arm in June.
A jury of seven men and five women has been selected for the trial, which is set down for three weeks.