Leonie Hutchinson was only 18 months old when she disappeared from Scone in Australia's Hunter Valley and was never seen again.
Thirteen years and two coronial inquests later, police now have fresh evidence that she may have been murdered.
"We hold grave fears for Leonie and certainly the evidence we will present to the coroner will confirm those grave fears," Hunter Valley crime manager Detective Inspector Trent King said.
"I can't pre-empt what's going to happen at court, but we have certain evidence that she may have come to a demise by the hand of somebody else, but again we can't disprove other aspects of it until we go through the court process."
Police only became aware Leonie was missing four years after she disappeared, while they were investigating an unrelated matter.
They have narrowed down the last time the baby was seen to August 2000 after conducting fresh interviews with people, including shopkeepers and residents in Scone, who knew Leonie and her mother, Kate Hutchinson.
Both were living in the upper Hunter town at the time and were well known in the small community.
Police are renewing their appeal for information about Leonie before a third coronial inquest begins on December 9 at the NSW Coroners Court in Glebe.
Hutchinson has previously told authorities her daughter is still alive and living safe and well with family. But she failed to identify the family or where they live.
She is believed to be living on the mid north coast and has been requested to appear at the inquest.
Detectives have spent the past six to 12 months reviewing old material and revisiting former associates of Hutchinson to canvas her and Leonie's last movements in Scone.
They have also spoken to people that may have been looking after Leonie at the time.
New evidence to be presented at the inquest includes results from further forensic analysis of DNA, which confirm the identity of Leonie's father.
Benjamin Turner, a former partner of Hutchinson, has previously claimed to be the father of Leonie.
"I can't confirm that at this stage because there are a couple of people that need to be spoken to before the inquest," King said.
Detectives have also visited schools across Australia to conduct further inquiries about girls of a similar age to Leonie, with similar features, place of birth and upbringing, although all lines of inquiries have so far been unsuccessful, he said.
No computer imagery has been constructed to predict how Leonie would look today.
Triggering people's memories about Leonie has been extremely difficult, particularly as the passage of time from her disappearance to now spans more than a decade, King said.
A former friend of Hutchinson gave evidence in the 2012 inquest about how Hutchinson had joined a witches coven when Leonie was born and had told her a "wolfman would one day come and take [Hutchinson] to the aliens".
King said that information was still being explored.
It is expected the inquest will run for at least two weeks.
- Sydney Morning Herald