Kahui twins' fatal hospital delay

Three month old twins Chris and Cru kahui were not feeding regularly before being admitted to hospital. Photo / supplied

A child abuse expert has told the inquest into the deaths of the Kahui twins he believes they were slammed against a surface.

Three month old Chris and Cru died of traumatic head injuries in 2006.

Their father Chris was acquitted of their murders two years later.

Dr Patrick Kelly has told the inquest the force involved was well outside the range of any kind of normal handling of infants on that age.

"Force certainly involved impact to the head for Chris and in my view, probably him being slammed against the surface. I think there's good evidence that the force to Cru also involved impact," he told the inquest.

Dr Kelly says the effect of the head injury on both twins would have been immediate and obvious.

A panel of medical experts has been giving evidence at the inquest into the deaths of twins.

Professor Carole Jenny from Brown University in Rhode Island told the inquest at the Auckland District Court that both babies were dehydrated when they died.

She referred to evidence that the twins were being fed every six hours and said that would be "unacceptable" for premature babies in the United States.

The babies were not feeding regularly before being admitted to hospital.

"Any baby who doesn't wake to feed in 12 - 15 or 24 hours... that should be markedly alarming to the caregiver."

She said she found that "mystifying".

"They would have woken and cried vigorously and obviously the reason they weren't waking and crying is that they had severe brain damage."

Prof Jenny said she was horrified nobody had noticed Cru's leg fracture, which would have caused him intense pain.

"Cru had tears in the cortex of his brain, and I can't imagine he would have been able to feed. He would not have cried normally either.

"Nobody noticed there was something horribly wrong as his leg was displaced," she said.