After more than 11 years, fresh information has been revealed about one of New Zealand's longest running and most mysterious unsolved murders.
Ashburton's Kirsty Bentley was just 15 when she disappeared on December 31, 1998, while walking her dog on the Ashburton riverbank.
The dog was found the next day tied to a tree and Kirsty's underwear was discovered nearby. It was not until two weeks later that her body was found 40km away in the Rakaia Gorge.
The case has never been solved and police have now released the facts they kept to themselves for years in hope it will lead to a breakthrough.
They have also revealed to TV ONE's Sunday programme how Britain's top expert on child murder, retired police inspector Chuck Burton, has been called in to help catch Kirsty's killer.
John Bentley, Kirsty's older brother, was the only family member at home when Kirsty took her dog Abby off for her daily walk.
She was seen heading towards the Ashburton riverbank just a few minutes away. A few hours later Kirsty's mother Jill Peachy arrived home and alarms bells began to ring when she realised Kirsty had failed to return.
"From that very first night I just knew she was dead, don't ask me how I knew, it was just something here had gone quiet," Jill says.
A huge homicide investigation got under way with hundreds of staff chasing down thousands of clues but to no avail.
Now, nearly 11 years later police have revealed information only they and the killer knew, such as how she was killed.
The latest officer to head the inquiry, Detective Inspector Greg Williams, says Kirsty sustained a major blow to the back of her head from possibly a long weapon.
Police have also revealed new information in that there was actually no evidence found to suggest a sexual or physical attack occurred near where the dog was found as was previously thought.
"We didn't find one skerrick of evidence that Kirsty physically was here....what I can say is that we've never been comfortable that this scene is the genuine scene where she was attacked," Williams says.
Police believe to get the dog's lead around the tree it had to be taken off her first.
"Well I think this is a mistake made by the person and gives us some insight into this person's knowledge of this dog, and control over the dog or control over dogs," says Williams.
Police are also revealing for the first time how Kirsty's body was left at Camp Gully near the Rakaia Gorge and that she was probably carried, wrapped in something and placed there. However, whatever she was wrapped in was not found.
"She had been placed in quite a respectful way, for instance her
sarong was right down to her ankles, she hadn't just simply been
thrown or cast in there," says Williams.
The area is thick with thorns yet there was not any damage to her clothing. In fact nothing was found there that linked Kirsty back to the Ashburton riverbank.
There is in fact no forensic evidence at the riverbank to show Kirsty was killed or sexually attacked there and at Camp Gully someone placed her body respectfully while also leaving no forensic evidence.
NZ police call in help
In order to make sense of it all New Zealand police turned to Burton for help.
Burton has made a career out of studying the murders of young people. He has helped put away some of Britain's most notorious killers and that is why Kiwi police working on the Kirsty Bentley case came to him.
Burton's resume makes for grisly reading - he has built a database of every child murder in Britain going back 50 years.
Burton took the Bentley case apart and says the lack of forensic evidence is significant and he is struck by the fact it was made to look like a sexual crime when in fact it was not. He says it looks to him as if the scene where Kirsty's dog and underwear was found was staged.
"It's to actually distract the inquiry from where it ought to be, it's an offender protecting his own identity by changing and altering the crime scene," says Burton.
He says the fact that Kirsty was dumped so far away shows the killer wanted to distance the crime from themselves and also shows a massive amount of local knowledge.
"I don't think the person who did this expected her to be found as soon as she was," Burton says.
He also says that Kirsty's body being left in a respectful way shows whoever did it cared for the victim.
"She wasn't thrown down there, she'd been carried, she'd been carefully placed, she's then been put in the foetal position, her clothing's been put back so she's covered, so her dignity is protected, and it just tells you that there is some sort of emotional connection between the offender and the victim," Burton says.
He says this connection could be anything from an acquaintance to a relative or parent.
Profiling an offender
Based on his investigation Burton has been able to form his own profile on the offender.
"You've got a dichotomy between what took place at the attack, this one massive blow which tends to be a younger offender, tends to be someone a bit younger, and then you've got this maturity in how the dog's been left, the pants have been left on the thing, how the body has been transported," he says.
This in his view suggests someone else may have been involved.
"I've got a view that someone helped, someone who's done something that they're afraid of, and someone that's very close to them that's actually helped him to put the thing right. Now that is just an opinion, that's an opinion I can't prove it and this isn't evidence, it's just an opinion," Burton says.
He says this analysis could point to what police have previously suggested, that Kirsty's dad and brother were involved.
"All you can do is interpret what you've got, and if the interpretation of what you've got unfortunately includes Sid and John, so be it, then I can't alter that&I'm not pointing the finger saying it is categorically them, but I can't alter the fact that they're in the mix," Burton says.
It was not until two years after the murder that John revealed police put it to him he killed Kirsty and that his father Sid was involved too.
Sid and John are two of hundreds of people police have considered in the inquiry.
Nine years ago the pair went public denying they were responsible for Kirsty's murder. They said police had put it to them that John killed Kirsty and Sid disposed of her body.
Police concern centres on Sid's claim he cannot recall his movements during the crucial part of the afternoon Kirsty went missing.
Sid still lives at the family home in Ashburton by himself battling alcoholism and failing health.
John now lives in England and studying to be an astronomer.
For the first time police have revealed their concerns with his memory of the day Kirsty went missing.
They say at first John told them he didn't hear Kirsty leave the house but then years later he told them he did.
Both Sid and John say they wanted to do whatever they could to help catch Kirsty's killer.
While they have not been eliminated from the enquiry there are a number of other people still of interest to the police.
Williams says there is a small group of 20 or so people of interest to them and other lines of inquiry remain wide open.
For example, police still have not eliminated the driver of a mysterious green van or the driver of a Ford Fairmont.
But after Burton's analysis their focus is on the killer being a local.
"It certainly reinforced our views around that, that it was someone local, someone who...knew Kirsty, or, or knew the area, or the scene," Williams says.