Slain boy's injury could have been days old - expert

Slain 3-year-old Dylan Rimoni could have been fatally injured days before he collapsed and was rushed to hospital, a British expert told an Auckland court yesterday.

Dr Waney Squier, a consultant neuropathologist, told the murder trial of Dylan's caregiver, Patricia Pickering, in the High Court that she couldn't be sure what the catalyst was for Dylan's collapse in April 2008.

The boy was placed on life support in hospital but died when it was switched off two days later.

Pickering was charged with murder after police alleged she slammed him against an unforgiving surface such as a wall, floor or door.

The 38-year-old denies the murder charge, two counts of causing him grievous bodily harm and one of assault.

Giving evidence for the defence via video link from Britain, Dr Squier said she worried that Dylan might have suffered from the "cumulative effects of trauma".

She agreed with an earlier witness for the Crown that Dylan had sustained multiple head injuries during his life but she couldn't be sure if the most recent was a few days old or up to a week.

The doctor told the court she believed Dylan could have been lucid after the critical blow, evidence in contrast to that of the Crown doctor, who said the collapse would have happened almost immediately.

Dr Squier, who has studied the case for the defence, said Dylan had been unwell in the days before he was hospitalised and had vomited, symptoms which were consistent with head injuries. "We don't understand what head injury is capable of doing in young people."

She compared slides taken from sections of Dylan's brain that looked similar to those taken from adolescents with head injuries. In those cases, the patients were injured, became unwell, and then suffered another injury - with severe consequences.

The so-called "second impact" cases have only just begun to be discussed by doctors.

"We don't know what happened to Dylan the night of his collapse because none of us was there," Dr Squier said. However, she suggested his vomiting could have been enough to trigger the second injury, causing his brain to start swelling.

Dr Squier also disagreed with Crown evidence on the cause of damage to Dylan's brain stem because she "couldn't convince myself" the damage was traumatic in origin.

"As an explanation for Dylan's sudden collapse I cannot be certain."

Prosecutor Phil Hamlin, in cross-examination, challenged the "second impact" theory, saying it was an unproven hypotheses that wasn't accepted by clinicians.

Dr Squier agreed it was unproven but said there were cases of young adults whose brain injuries were virtually exactly the same as Dylan's.

Mr Hamlin asked her about criticism she'd received from a judge after giving evidence in a case in Britain. She was accused of "shoe-horning the evidence to fit a minority view". Another judge said she was disingenuous in the articles she put before the court by another.

Dr Squier said she refuted all the criticisms but couldn't discuss the cases because of suppression orders. The trial in Auckland is continuing.