Witness from Ben Smart and Olivia Hope murder mystery dies suddenly

A key witness from the trial of convicted murderer Scott Watson has died suddenly in a suspected suicide.

Furneaux Lodge worker Guy Wallace was one of the last people to see Ben Smart, 21, and Olivia Hope, 17, alive on New Year's Eve 1997 after dropping them at a boat.

He gave evidence of another man being with them, although that man was never identified. The Crown contended it was Watson.

Wallace was operating a water taxi on that night and was a key witness for the Crown at the murder trial. However, he was adamant he dropped Ben and Olivia at a double-masted yacht. The Crown insisted it was Watson's single-masted boat.

When asked in the witness box to compare Watson's boat to the one he described to police, Wallace said: "The only similarity is that they both float."

Wallace had been working at the Marlborough Sounds lodge serving drinks and took people in a water taxi out to their moored boats after the party wound down.

Smart and Hope were never seen again after the last sighting by Wallace.

Scott Watson in the High Court Christchurch in May 2015. Photo/ File

Wallace, who had been living in Greymouth, was found dead on Monday.

His death has been referred to the Coroner.

Watson told a parole hearing in December last year he was unable to get psychologist treatment behind bars because he wouldn't confess to the murders.

Watson, 49, was denied parole for the third time.

Ben Smart and Olivia Hope vanished on New Year's Eve 1997.

He made his latest attempt at freedom in front of the Parole Board at Rolleston Prison, south of Christchurch. At the conclusion of the hearing, panel convenor Sir Ron Young told him: "It's a no to parole, which perhaps won't surprise you."