A mortuary technician who helped conduct the autopsy on Lachlan Jones says there were no signs the Gore boy's body had been put in a freezer before it was found.

Two police investigations found the 2-year-old accidentally drowned in a council sewage pond in 2019, but his father Paul Jones disagrees - and opposed an autopsy.

The inquest is entering its third week in Invercargill with accusations of body-dumping, fake alibis, a botched investigation and neglect.

Lachlan's half brother has faced accusations from Paul Jones' lawyer that he put the little boy's body in a freezer before dumping it at the sewage pond.

But mortuary technician William (Bill) Little - who helped to conduct the autopsy - said Lachlan's fingers and ears were not shrivelled like they had been frozen.

"We took vitreous fluid from the eyes as a part of samples that we took and that was clear," he said.

"If you know what a fish that's been frozen, the eye goes sort of misty, misted over. Well, Lachlan's eyes were crystal clear as the fluid that we drew was crystal clear."

Lachlan appeared to be a well-nourished young boy, he said.

The autopsy team - himself and a pathologist whose name is suppressed - was given no information to suggest anything suspicious had happened, he said.

"The general conversation once we'd both read the Pol 47 (a report the police prepare) was that it is a routine procedure," Little said.

"There was nothing at all there to indicate to us that there was a suspicious or unexplained cause of death."

Little also fielded questions about missing photos, which he said were lost when the mortuary computer was disposed of after the mortuary was decommissioned from doing coronial work.

Coroner's counsel Simon Mount KC asked him why the autopsy was not as thorough as the one initially requested, and why the phone call with a duty coroner that led to that change was not recorded.

"That is what the procedure should have been. But in this case I don't there was a redirection issued," Little said.

'I think he was just on a little adventure'

Preschool teacher Leisa Diamond described Lachlan as a well-behaved boy with a good grasp of right and wrong.

His mother told the inquest earlier that he had run away with a full nappy when she tried to change him on the night he died.

Diamond said that was not the Lachlan she remembered, but in response to questions from police lawyer Robin Bates, she said children could act differently at preschool than they did at home.

When asked if she thought he could climb the wooden fence near the sewage pond, she said it would be very difficult and she did not think he would have any interest to try to do it.

In her statement, she said Lachlan was not one to run away.

She was also asked to explain why she had said she could imagine Lachlan going off an adventure while pretending to be a police officer.

"At that time, I didn't know any other facts. How long it was, where he was found, any of those other - what he had to go over so I think in what I had in my head was he was just on a little adventure being a police man," Diamond said.

The inquest continues on Tuesday.

Reproduced with permission