"Without a doubt.
"The majority of cases I've ever dealt with you kind of know what happened ... but Graeme's case I've just got absolutely no idea.
"All the conclusions, all the possibilities, all the scenarios just don't make sense."
When Mr Bainbridge began looking in to Mr Timlin's disappearance he got in touch with the Timlin family and has stayed in contact ever since.
He said he would be attending the inquest with Mr Timlin's 88-year-old mother.
He understood she had been told that following a 1977 coronial inquest that found her son missing presumed dead, no death certificate was ever issued and signed. He said this inquest will be to formalise the death and file paperwork.
"It'd be nice to say that the police acted on what I presented and carried out an investigation and came up with something more tangible , but I've got a feeling it's an exercise to finalise their paperwork.
"They've pretty much said to his mum that it's to finalise a death certificate. In some respects it's good, but for her she doesn't see the sense in it.
"It's dredging it all back up," he said.
"She understands that's what she'll have to listen to."
Mr Bainbridge said some weeks after Mr Timlin's disappearance a fisherman reported to police a man's body in the ocean near Kawau Island that fitted the his description.
However, a search by police failed to find any trace of the body.
Mr Bainbridge puts forward in his book the theory that an aggrieved ex-employee of Mr Timlin was the only person who may have had a motive to kill him, however he said the disagreement wasn't strong enough to really justify murder.
The coronial inquest will be heard on Friday at the Hamilton District Court before Coroner Gordon Matenga.
