If you've ever read a book about the murders of Olivia Hope and Ben Smart, you'll need to read Elementary, too.
In fact, it will help immensely if you've read other books about the murders. Ian Wishart's second run at the Marlborough Sounds' murders of New Year's Day 1998 is not a great literary effort.
It is, though, a detailed account of the evidence police used - and more importantly did not use - to convict Scott Watson. The evidence includes chunks of material that has never been made public, and Wishart has used it to build his own case against the convicted murderer, currently serving his 17th year in prison.
The book does three things. First, it gives people a different picture of Watson. Much of what has been written in the past 15 years has raised questions about the police case, but has had the byproduct of softening Watson's image from convicted murderer to someone potentially mistakenly jailed.
Elementary "doesn't pull any punches", Olivia's father, Gerald Hope, told me yesterday. He's right. Wishart has included a large number of unsubstantiated statements made to the police during the inquiry - claims that have never been tested at trial.
What emerges is the portrait of someone who is very different from the "airbrushed" public image, as Wishart calls it.
The second thing the book does is take the prosecution case away from police. To understand how, consider the material that has been available to Wishart. When police investigate murders, they canvas widely. Evidence accumulates from a wide range of sources and it is all catalogued and retained.
From this, the prosecution creates the case against the accused. It is meant to be the methodical building of a structure which, ultimately, shouts "guilt". In the end, evidence that does not contribute to the structure is left behind.
The electronic file obtained by Wishart contains all the original building blocks. It was provided to the defence as part of the legal discovery process, and later obtained by Wishart after passing through a number of hands.
His structure may be shaky. Police have yet to consider the book and may wish to knock it over. But, for others, it might answer a few questions.
Finally, the book serves as a vehicle by which Wishart has attacked those who have previously written on the case, particularly Keith Hunter, who wrote Trial By Trickery. Hunter's book is considered by those supporting Watson to be a solid demolition of the police prosecution.
Wishart doesn't think so. He doesn't spare others, but Hunter really cops it. Chapter after chapter, Elementary batters away at assertions made in Trial By Trickery. There is even a chapter called "Keith Hunter's Taxi Theory Sinks".
If someone can get Hunter and Wishart into a televised debate on their books, it will be compulsive viewing. I can't imagine it would end well.
Wishart has done well to get his hands on the file. His gathering of the material into a book isn't done quite as well - there are large chunks of cut-and-pasted statements that don't seem to add a great deal. In most places, the storytelling gives way to the polemics against other authors.
But Wishart has never claimed to be New Zealand's Norman Mailer. He has claimed to be - and is - an investigative journalist with an amazing knack for digging up interesting content. Elementary has plenty of that.
SOUNDS MURDERS SPECIAL REPORT
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• Wishart: Sounds case solved
• Careful tracing of boat clears Watson, says author
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