KEY POINTS:
A forensic paediatrician says it was very difficult to pinpoint when the Kahui twins were fatally injured but believes a seizure by one of the boys may have happened hours after the initial assault.
Dr Terrence Donald, a forensic paediatrician from Australia, told the High Court in Auckland today it was likely Cru Kahui suffered a seizure which caused him to stop breathing from the secondary effects of an earlier assault.
Dr Donald was the last witness for the defence.
He said a person who was not familiar with the babies or was not their main carer may not have been aware of anything wrong with them.
Chris Kahui is charged with the murder of his three month old twin sons Chris and Cru Kahui.
The crown says Kahui fatally injured the twins on June 12, 2006, while the defence say someone else, probably the twins' mother Macsyna King hurt them.
Dr Donald said it was likely a primary incident was likely to have caused the haemorrhaging and lacerations to the brains of the twins, causing them to become unconsciousness.
The twins' level of consciousness would have improved to an altered state of consciousness, with the seizure by Cru Kahui on the Monday evening June 12 probably a secondary effect of the initial assault, he said.
Dr Donald said the seizure was likely a secondary effect, as a result of swelling in the brain.
Signs of the secondary effects could happen between four to six hours after the assault and it was very difficult to accurately say when the twins were hurt, he said.
"The problem is being able to recognise they have specific nature of altered conscious in babies of this age."
Dr Donald said the twins were so young that medical experts were constantly asking how to modify what is known about babies even a month older and how they responded in similar incidents to compare it to the Kahui's age group.
Given the twins' age and that they were premature, it was even more difficult, he said.
Dr Donald said the only way to determine the timing of the injuries was from a reliable person who could say when the babies were last normal.
"There is no independent person here to determine that."
Dr Donald said he did not consider a carer as an independent person and that fathers in particular had difficulty interacting with newborns or knowing what was normal behaviour.
Dr Donald disputed evidence by crown witness Dr Patrick Kelly that the twins would not have been able to feed after being assaulted.
Evidence given by April Saunders she had fed one of the twins, thought to be Cru, on the Monday morning, did not prove whether the twins had been assaulted by then or not, he said.
"He could have sucked but the question is would he have fed normally?"
Dr Donald said it was possible for a baby with those fatal injuries, to hold milk in its mouth when being fed and possibly be able to swallow and initiate a sucking reflex.
"The baby may be able to swallow it but that would be the limit of it."
Dr Donald said he was struck by how little people seemed to appreciate the twins' condition.
"It either wasn't as bad as it ended up or no one was able to assess their condition."
Under cross-examination Dr Donald said there was no evidence prior to Cru receiving CPR that the twins were fatally injured.
Under re-examination Dr Donald said prior to CPR if the twins were asleep there would be no obvious signs if they were unconscious.
The trial continues tomorrow with the crown making its closing statement, which crown prosecutor Simon Moore has said is expected to take more than a day.
- NZPA
