Author Ian Wishart's second book on the Scott Watson case will be published next week.
Mr Wishart claims Elementary 2.0: The Unreleased Police Evidence on the Scott Watson Case will outline five key reasons why Watson is guilty of killing Ben Smart and Olivia Hope. The friends disappeared after boarding a mystery yacht moored in the Marlborough Sounds in the early hours of New Year's Day 1998.
Watson was convicted on their murders the following year and remains behind bars, although he has steadfastly maintained his innocence.
The book follows the January publication of Elementary. Its sequel will see the release of hundreds of pages of police evidence, and these put Watson "clearly in the frame" for the murders, Wishart said.
"It was always my intention to release the full police evidence of key witnesses.