Baby Karlos Stephens could have survived between five and six hours after he suffered the head trauma that ultimately killed him, a court has heard.
The evidence came before the Crown wrapped up its case in the murder trial of Shane Claude Roberts this morning.
A neuropathologist and the clinical director at Starship Hospital both took the stand this morning exploring how Karlos may have presented after he suffered the fatal head injuries and the level of force required to cause them.
Roberts, 61, is standing trial for the murder of baby Karlos Stephens back in 2014. His trial began in the High Court at Rotorua last week.
Professor of neuropathology Colin Smith gave evidence from audiovisual link from Edinburgh.
Smith told the court that he observed that baby Karlos had suffered "two episodes of trauma" on his brain that caused bleeding, with one of them happening "at least several days" before his death but he survived it.
He said this sort of bleeding and hemorrhaging in an infant was a "rare event" and it was not done by "simply falling over" but instead from "high-velocity trauma".
Changes in his brain cells had shown that Karlos had survived for a period of time after the injury with evidence suggesting it could have been between five and six hours, he said.
However, his heart would have been struggling and he would have been "critically ill" almost immediately, he said.
Previously, Karlos' mother Pamela Stephens had told the court that Karlos had been "grizzly" and just wanted to be cuddled the day before his death.
When asked if this was common behaviour from a brain injury, he said it was not, as a baby who had suffered a "terrible head injury" like Karlos would not be responsive.
He said if he had got medical attention immediately after the injury he could have survived but would have been left with brain injuries.
Starship Clinical Director associate professor Patrick Kelly took the stand and said there was "absolutely no doubt" that Karlos suffered a "significant" head injury.
Passengers in a car crash who were not wearing a seatbelt, being hit by a car or falling from a height of more than 2m were some of the "accidental cases" where infants had subdural brain bleeding like Karlos, he said.
He said this showed the level of force involved to do this sort of damage.
Children who suffered a head injury could possibly start vomiting and become unresponsive almost immediately, he said, and in cases of those under 2 years, they could stop breathing and sometimes go blue.
He said he was confident that no one would carry on as usual.
The retinal hemorrhaging or bleeding behind the eyes found in Karlos was typical in "abusive head trauma" and rare in accidental trauma, he said.
When asked whether evidence that Karlos had suffered a previous head trauma would have anything to do with his death, he said he did not believe it did.
Instead, it may have an impact on a person who inflicted the injuries, who may assume the child would wake up or recover like they did the first time, he said.
Kelly told the court that Karlos appearing "floppy" upon arrival at the hospital indicated that he was most likely already dead.
The crown has wrapped its case with the defence set to start this afternoon.
The trial continues.