neuropathologist.

An expert could not tell if a 17-month-old was hit in the head with a solid object before her death, or if her head was hit against it.

Sadie-Leigh Gardner died in Tauranga on 29 March 2019.

The toddler's death was the subject of two previous trials after her stepfather Adrian Clancy was charged with murder. He was found guilty and then acquitted by the Court of Appeal and found not-guilty in a retrial.

Coroner Tracey Fitzgibbon is looking to establish how and when Sadie-Leigh sustained her injuries, and if they were accidental.

Neuropathologist professor Colin Smith told the inquest there were only two options as to how she got the injuries.

"Whether or not an adult has struck a solid object off this child's head, or whether the child's head has been hit against a solid object, I can't say."

He said there was no scenario he could imagine where the child was able to sustain these injuries independently and without anyone else involved.

"I very strongly feel this has been an inflicted injury. A 17-month old-child has not done this to herself, so someone has caused this injury to happen.

"Whether that was intentional or accidental, I can't say. But it's a very significant level of force that has caused this. This is not a bumping a head on something accidentally.

"There's a very significant level of force to cause such a big skull fracture with such an amount of soft tissue swelling and bleeding with the big blood clots that have followed. This is a very significant level of force."

But he said he was unable to determine exactly when the injuries would have occurred.

In regards to the timing, lawyer Rob Stevens put to Smith that two scenarios were being considered based on the medical evidence.

"We know that when the child was put to bed around 3pm, she appeared to still be well. So the first scenario is that the trauma to the head was inflicted between 3pm and 3.31pm and the child was found very unwell in her cot at 3.46pm.

"The second scenario is that the injury was caused between 3.31pm and 3.46pm."

Smith said there was nothing he could determine that would differentiate between those two scenarios.