When Warwick Jenness speaks of the murders of Olivia Hope and Ben Smart, he does so without speculation.
There is a certainty to the statements he makes based on four years of solid, informed research.
He is not one to make hasty decisions. Others well-versed in the case worked with Jenness - a communications engineer, commercial pilot, company director and recreational sailor.
Their findings coalesced into a report that traces the route taken by the infamous "mystery ketch" to Furneaux Lodge in the Marlborough Sounds for the New Year's Eve party of 1997. This is the vessel to which police first looked to answers over the question of the disappearance of Hope, 17, and Smart, 21.
In meticulous detail, Jenness' report describes who was aboard. Scott Watson, convicted of murdering the young pair, is not among the names.
Then, in a series of startling claims, he builds a theory around the disappearance of Hope and Smart, which explains Watson's absence. It diverges completely from the prosecution case which saw Watson convicted of their murders and sent to prison for 19 years.
Along the way, he gives Hope and Smart a few more days of life. There is a supposed sighting on January 3, two days after they were meant to have been killed, and a photograph of someone on the back of a runabout which they claim is Hope.
It was taken on January 5.
If only police had focused on the ketch, the report states, because if they had then "Ben Smart and Olivia Hope could well be alive today leading normal lives with their families instead of missing, presumed dead".
Mr Jenness is not the only one to claim to have identified the ketch.
A new book by Ian Wishart is due for release tomorrow and also claims to have found the yacht. It will be the fifth book written on the Sounds murders.
For many, the disappearance and presumed murder of Hope and Smart is one of New Zealand's most captivating and enduring mysteries.
For others, there is no mystery. The killer, police and others will say, was found guilty after an 11-week trial in 1999. Convicted, Watson remains in prison, denied parole and still maintaining his innocence.
"You're wrong," he told the jury 17 years ago. He has the same message today.
The yachting community had many vocal opponents of the case against Watson. As the case unfolded in court, the prosecution's assertions on issues with which yachties were familiar created a small but determined group of naysayers.
Key to it was Watson's yacht - a small, single-masted vessel - and testimony Hope and Smart were last seen boarding a 40-foot two-masted ketch. Yachtie Mike Kalaugher wrote a 2001 book on the case. He said there was no way to confuse Watson's boat with a much larger ketch. "This is equivalent to confusing a truck with a Mini."
The hunt for the ketch was where Mr Jenness started, along with Mr Kalaugher and Keith Hunter, author of Trial By Trickery, which makes compelling arguments against Watson's conviction. Mr Jenness told the Herald: "If we can prove that the ketch existed, and I think we have, then Watson is not guilty."
The report begins with the first sighting of the "mystery ketch" - 40ft with a wide blue stripe, distinctive rigging and portholes along its side - seen in the background of a television documentary filmed in Tonga. Tracking back through the Pacific, the report claims to have tracked it to Vanuatu and then Noumea, quoting a yachtie as speaking to its owners as they left it behind. According to the report, it was sold for cash in late 1997 in an "unusual", "fast turnaround" sale.
"The ketch would have departed from Noumea in the later part of November 1997 for New Zealand with a likely rendezvous en route to load and conceal on board a significant consignment of illicit drugs," the report states. It is drugs, and those in the drug world, the report ultimately blames for the disappearance.
From there, the report traces the ketch - through witnesses including harbour masters and sailors - from New Plymouth to Nelson and then into Marlborough Sounds. On the journey south, the report begins to introduce characters - named - who are said to have an association with the ketch or those aboard. It details the sightings of many who saw it - accounts drawn largely from police evidence.
Mr Jenness says the scenario described by police that New Year's Eve cannot have happened. "[Watson] may have rubbed shoulders with the kids in the bar but he never spoken to them. The case against Watson has little bearing on what happened."
Watson left early the next morning, but the report from Mr Jenness also has the ketch setting off before many rose from the night's partying.
By January 2, the person named as skippering the ketch was "faced with a dilemma" - "what to do with Ben and Olivia". Possible sightings of Hope, previously raised, led the authors to sketch a route ending at Nelson. There, it claims, Hope and Smart were off-loaded into a van as the drug deal reached its pinnacle.
The connections drawn, described as "quantum leaps" by Watson's dad Chris, appear to be Mr Jenness' efforts to connect the sightings to the claim Hope and Smart were seen alive - but scared - at the Federal Hotel in Picton. It is a sighting which has previously been raised, but dismissed because it was believed to have taken place on New Year's Eve. It was dismissed in part because Hope and Smart were at Furneaux Lodge that night, and in part because the witness was intoxicated.
Mr Jenness, though, believes he has proved the sighting was actually on January 3. And that night, he says, the witness was sober. That evening, evidence shows, Watson was far away on a cruising holiday with his sister Sandy.
He claims another sighting two days later - January 5 - which is the most astonishing assertion in the report. By then, according to the report's chain of events, Hope and Smart had been transferred to another yacht owned by someone allegedly with convictions for serious violence.
A photograph, distant and grainy, shows a flash of blonde hair on a runabout. It was taken by a woman named in the report who reported a "girl with long blonde hair clearly blowing in the slipstream". There was a young man also with her. "Both appeared to be sitting with their hands behind their backs as if ... tied."
The woman's husband called police - "it was three months before NZ Police followed up the information", the report claims.
A day later there is another sighting of the boat. At that point, the authors conclude, Hope and Smart are no longer aboard.