Experts have begun days of putting their views on child abuse studies and the particular injuries suffered by a 17-month-old toddler before a Christchurch District Court jury considering injuring accusations against a 24-year-old man.
The evidence of paediatrician Dr Patrick Kelly is expected to be followed by testimony from another expert called by the defence, who has been observing in court.
The trial before Judge Brian Callaghan is now in its fourth day and expected to last all week, Christchurch Court News website reported.
Dr Kelly told the court there needed to be "a very significant degree of force" to cause the subdural haemorrhage injury evident in the Christchurch girl.
He described the type of force required as violent.
"It is outside the realm of normal handling of a child."
The injury had killed much of the left side of the brain. She had a tear to a bridging vein, brain swelling and injuries scattered through other areas of the brain.
He said it was extraordinarily unlikely that a fall from a low height would cause the damage to the vein as well as the distribution of injuries seen in this case.
He said he was reluctant to use the term "shaken baby syndrome" in this case.
"I don't know what happened to (the toddler). It could have been shaking. It could have been shaking plus impact, or impact alone. All of these things involve far too much force being applied to the head."
Impact could leave no signs of impact - such as a bruise - to a child's head. Impact against a padded surface might distribute the force enough so that there was no visible injury at the point of impact.
Crown prosecutor Mark Zarifeh described how the crown case was that the injury to the girl was caused during a time when the man had put her in a "time-out" in a bedroom, on a day when she was irritable and being naughty.
Dr Kelly said falling was a frequent event for active toddlers.
He was told of this girl falling out of bed, jumping off a table, or climbing out of her cot on other occasions. He was shown photographs of the bedroom, and asked about the possibility of her falling after climbing on the bed or bedhead.
He thought it was "highly unlikely" that she could have sustained the major brain injury from such a fall.
"The number of bruises on her body suggest she has been grasped very firmly around the body and I can't see how she would have got these bruises in falling off the bed."
Cross-examined by defence counsel Richard McGuire, Dr Kelly agreed that he saw impact as being more likely than shaking to have caused the injuries, and yet there was no sign of serious impact to the outside of the girl's head.
Mr McGuire referred to a 2007 report from the defence expert witness, who said there was no direct evidence of damage to the brain, and it was the swelling to the brain which had resulted in the escalating condition that saw the girl admitted to hospital.
Dr Kelly acknowledged that would remove one of the grounds for thinking more serious force was involved.
The partner of the child's mother denies a charge of intentionally causing grievous bodily harm to the toddler, and an alternative charge of causing grievous bodily harm with reckless disregard for the girl's safety.
The names of the man, the child, her mother, and grandmother have all been suppressed. The crown alleges the brain injury occurred on October 25, 2006.
