"He will be shivering in his boots I would think," Prof Newbold said.
"It's really difficult to say what the guy will be doing now. It's so odd and unusual and we don't know why on earth he would do something so dumb.
"The little girl, she was probably bewildered."
The man might not even be sane, but if he was, would be pretty scared given the public attention on the case.
"It's puzzling. I wonder if he knew what he was doing. I wonder if he had any idea or any plans. Those kinds of crimes often end up in the death of a child.
"The typical scenario there is abduction with sexual intent and it leads to the death of a child," Prof Newbold said.
"Why else would you do it, unless you knew the person."
Other possible scenarios included ransom for cash, which was rare in New Zealand and unlikely in this case, or an alienated relative in a custody dispute. Again, that was unlikely, he said.