A new book claims convicted murderer Scott Watson is the person who killed Olivia Hope and Ben Smart despite Watson's claims he has been wrongly convicted.
The claim is made by journalist Ian Wishart in Elementary - published today - and comes as a former senior detective in the case details an extraordinary claim that Watson had confessed to the killing.
Wishart's book comes 17 years after Watson was convicted of murdering Ms Hope, 17, and Mr Smart, 21, on New Year's Day 1998.
Watson has always denied any involvement but the new book claims police got the right person, although they contorted evidence to fit a prosecution scenario in which the bodies were dumped in Cook Strait.
Wishart said the decision to use evidence that fitted a scenario covering the missing bodies created questions over the case and led to 17 years of speculation about the murders.
The Herald has been given exclusive access to the critical chapter in the book in which Wishart lays out three alleged sightings of Watson on New Year's Day - the day the murders were said to have been committed - in an area in which he had always denied being present.
The statements also claim a second person was on the boat, leading Wishart to allege Watson had an accomplice. The statements on which Wishart draws include claims that Watson's boat Blade was being painted while at sea. Wishart accuses a key witness with name suppression, dubbed "Keating" in the book, of manufacturing an alibi to protect Watson from scrutiny. He claims the new statements destroy the evidence from Keating, who has since died.
The book is drawn from the contents of the police investigation file which was provided to Watson's defence and then distributed to other parties, one of whom passed a copy to Wishart.
Wishart's 1999 book on the case cast doubt on the prosecution - a stance he has changed. Wishart told the Herald last night: "Having now seen the evidence they didn't use, but should have used, I'm absolutely confident Scott Watson is the killer of Ben and Olivia."
Ms Hope's father, Gerald, last night welcomed publication of the book as "the most in-depth review of statements I've ever read" on the case, with new material of which he was previously unaware.
"It brings balance back to the trend of 'he's wrongfully convicted and is therefore an innocent man in jail'."
Mr Hope said he had applied through the Department of Corrections to meet with Watson. "There are questions which have not been asked, let alone answered, and he alone can provide that information."
He said there had been criticism - which he had also voiced - about flaws in the police case. "If only they had been a little bit more thorough and methodical in the process it would have removed doubt. But it comes back down to Watson, whether he was guilty as proven, whether he wants to show remorse and accept what he has done."
The claim of a confession is included as a 50-word post-script in the book but was detailed yesterday to the Herald by Detective Senior Sergeant Wayne Stringer, now retired. He said "Keating" told him of a conversation he claimed to have had with Watson the day after the murders.
Mr Stringer said he had become close friends with Keating, having met him when appointed as his bail officer by Detective Inspector Rob Pope, the officer leading the investigation into the murders.
He said the relationship developed until they were like "family".
After Watson was convicted, Mr Stringer said he and his wife were at a dinner with Keating, who laid out what he claimed was a confession made by Watson on New Year's Day in 1998. "[Keating] told me that Scott Watson had told him what he did."
Mr Stringer said that according to Keating, Watson attacked Ben Smart and "stabbed him to death" and then "stabbed her [Olivia] to death".
Keating also claimed Watson told him he wrapped them in sails and spare chain and took them out to where they would never be found, and dropped them off.
Mr Stringer said he knew Keating well and trusted him. "He didn't have any reason to tell me lies. I believe him absolutely ... I have no doubts about [Keating]. He was a bad guy but he was a good man."
Corrections deputy chief executive Vincent Arbuckle confirmed a request had been made to visit Watson and was being assessed.
Scott Watson is serving at least 19 years in prison for the murders of Olivia Hope, 17, and Ben Smart, 21, who disappeared on New Year's Day 1998. Watson has always denied involvement in the murders. Questions over his conviction include:
1 Watertaxi operator Guy Wallace dropped Olivia Hope, Ben Smart and a "mystery man" at a yacht he described in detail as a ketch. It was the last sighting of the two young people. Wallace initially identified Scott Watson, who was convicted of the murders, as the man who was with Hope and Smart, but later retracted his identification. However, he has not moved on his description of the ketch. Wallace was a key witness for the Crown.
2 Wallace's description of the vessel to which he delivered Hope and Smart led to an initial search for similar craft. There were a number of sightings of a 12m ketch (a two-masted vessel) as described by Wallace. Police have been accused of ignoring the ketch angle and focusing on Watson and his 7.2m single-masted sloop, Blade. The Crown has used photographs of the bay on New Year's Eve and New Year's Day to rebut claims of the ketch, but it has also been claimed it came and went during the night.
3 Rozlyn McNeilly was also a key identification witness for the Crown. She identified Watson as being the man she served at the bar of Furneaux Lodge on New Year's Eve, linked by police to the murders. She has also retracted her identification, saying she was tricked by officers. The Independent Police Conduct Authority was critical in 2010 of the police identification process.
4 The identification process has been intensely criticised. The "mystery man" description and the identikit issued by police based on those descriptions show an unshaven man with shoulder-length hair. Images taken on New Year's Eve show Watson as clean-shaven with tightly cropped hair. There was also a claim the "mystery man" had hooded eyes, as illustrated in a photograph of Watson shown to witnesses by police. It emerged the photograph was taken when Watson was blinking and his eyes half-shut.
5 One secret jailhouse witness testified that Watson confessed in prison. The inmate later retracted his claim.
6 Another secret jailhouse witness has had his credibility questioned after it emerged he received assistance from the police after testifying.
7 Guy Wallace has offered further information which increased speculation about the ketch, naming a specific location were he claims to have seen Hope, Smart and the "mystery man".
Although police say Wallace took Watson - "the mystery man" - to a boat in the bay with Hope and Smart, another watertaxi driver named John Mullen emerged to say he ferried someone resembling Watson to a boat. Watson had previously described the watertaxi operator who had taken him to Blade, and Mullen fitted that description.
Witnesses on a boat alongside Blade have given a version of events that competes with Crown testimony about Watson being returned to Blade.
10 The only DNA evidence in the case were two blonde hairs matched to Hope from a blanket inside Blade. They were not present on the first search of 400 hairs but were found on the second search - the same day Hope's hairbrush was present in the ESR lab.