Police have spoken about a new TV docu-drama examining Scott Watson's conviction for the 1998 Sounds murders, saying his conviction is based on evidence heard and tested in several courts.
In one of New Zealand's most controversial cases, 17-year-old Olivia Hope and Ben Smart, 21, boarded a yacht in the Malborough Sounds with a man in the early hours of New Year's Day 1998, and were never seen again.
Eighteen months later Watson, from Picton, was convicted of their murders. He has always maintained his innocence.
Next Sunday, TVNZ docu-drama Doubt: The Scott Watson Case questions the evidence that led to him being jailed for the crime.
A police spokesman responded to Herald on Sunday requests for comment by saying "the evidence against Scott Watson has been heard and tested in several courts, including the Court of Appeal".
"The Operation Tam investigation has also been scrutinised by the Independent Police Conduct Authority. Mr Watson's conviction by a jury is based on consideration of all the evidence, not just individual pieces of the picture," the spokesman said.
"This includes witness testimony corroborated by the facts."
He said police were "unable to publicly re-litigate selective aspects of a historic investigation - Mr Watson has the option of raising such matters through the appropriate judicial process."
Olivia Hope's parents, meanwhile, say they will tune into a new TV docu-drama about her killer - but fear it will be traumatic viewing.
Olivia Hope's father Gerald told the Herald on Sunday he and his wife Janice had turned down an offer to participate in the programme.
"We felt it would open old wounds, so why relive the pain and anguish of losing our daughter under those circumstances" he said.
"We decided there would be no value in it for us to sift through it all again.
"There is more than sufficient comment about the case in the public space now and there is more than adequate video footage of the trial, so we said no."
Hope said the family was fully informed of the intention to make the programme and of its contents before Production Shed TV was granted more than $1 million in funding by NZ on Air.
The family was also offered a private preview ahead of it screening but declined.
"We will just wait and watch it next week along with the rest of New Zealand."
Doubt: The Scott Watson Case will air as part of TV One's Sunday Theatre series.
The presenter, Massey University law professor Chris Gallavin, will argue Watson is a victim of miscarriage of justice because the trial and investigation were unfair.
The programme will reconsider forensic evidence and key witnesses will speak publicly for the first time about what they saw.
In November 1999 Watson was sentenced to life in prison with a 17-year non-parole period.
Gerald Hope said Watson could be out next year but he was hopeful of meeting him in prison soon.
"The fact is, he has served his time and could get parole," Hope said.
"The Department of Corrections and Watson's lawyer have been in discussions about us meeting.
"My wish is to meet him as soon as possible, hopefully in December. There are a few things that don't stack up and I still want to ask him a few questions."
Smart and Hope were among hundreds of party-goers at Furneaux Lodge in Endeavour Inlet in the Marlborough Sounds on New Year's Eve 1997.
Water taxi driver Guy Wallace said that, in the early hours, he dropped the pair and a man at a two-masted yacht in the inlet.
Smart and Hope were never seen again and their bodies have not been found.
Scott Watson was also in the Marlborough Sounds, on his single-masted sloop, Blade.
Although neither he nor his boat fitted Wallace's descriptions, Watson was arrested in June 1998.
Last year Watson gave his first media interview to North & South magazine - and maintained he had no involvement in the disappearance of the pair.