A prominent sportsman has been charged with causing the injuries and the prosecution told the jury at the Dunedin District Court it probably occurred during a moment of frustration when the child’s mother was at the gym on July 16, 2023.
The man, who currently has name suppression, has pleaded not guilty to injuring with reckless disregard, as well as an alternative assault charge.
Dr Juliet Soper, who was a consultant paediatrician at Starship Hospital at the time, told the court today it would take a "high magnitude of forces" to cause rib fractures to a baby.
But the defendant and the infant’s mother told police repeatedly they had not caused the damage, nor could they come up with any viable theory as to how the injuries may have been caused accidentally.
There was a suggestion the mother may have rolled on the baby while co-sleeping but she said she could not recall a situation where that occurred.
Dr Soper said the injuries would not have been sustained while the child was on his back on a bed.
"The magnitude of the force required to cause rib fractures in children is large," the witness said.
"Rib fractures are not caused by common infant-care activities."
As other Crown medical experts have said throughout the trial, Dr Soper did not believe there was evidence of any bone-fragility disorder that meant the child was any more susceptible to fractures.
The infant was diagnosed with severe vitamin-D deficiency when he was admitted to hospital but the doctor concluded that alone did not increase the risk of bone breaks.
"As a paediatrician I rely on factors from history, physical examination, laboratory testing and medical imaging reports to reflect a diagnosis," she said. "No one factor is considered in isolation."
Prolonged lack of vitamin-D can lead to rickets in its most serious cases, but Dr Soper and other experts opined there was no evidence of the disorder in the baby.
She cited one study which showed 94 children admitted to hospital with rickets, presenting with 216 fractures between them.
None of them featured rib breaks, she said.
"In the absence of an obvious accidental trauma mechanism, inflicted injury needs to be considered the most likely cause of [the] rib fractures," Dr Soper said.
"One plausible mechanism . . . is squeezing of the infant’s chest."
Dr Soper is the final Crown witness.
The defence case is expected to begin next week when several other medical experts will be called.
