Colin Thatcher makes his way to a parole hearing at the Ferndale Institution in Mission, B.C. in December 2004. The former Saskatchewan cabinet minister spent 22 years behind bars for murdering his ex-wife. (Chuck Stoody/Canadian Press)

An independent publisher expects to have a book by Colin Thatcher, convicted of killing his ex-wife, on store shelves this fall.

The 440-page true-crime memoir is titled Final Appeal: Anatomy of a Frame.

A publicist for ECW Press in Toronto said the book includes Thatcher's account of the murder and his 22 years in prison.

It also presents undisclosed evidence that Thatcher uses to question the administration of justice. He has always maintained his innocence.

Jack David, publisher of ECW Press said he was initially skeptical of Thatcher's continued claim of innocence. Then he read the manuscript.

"If people actually read the book, I think some people will be convinced, like I was, that there's reasonable doubt there," David said in an interview on Wednesday.

The book is tentatively set for release on Sept. 1.

'We don't ultimately find out who did it.'—Publisher Jack David

A jury found the one-time Saskatchewan cabinet minister guilty of first-degree murder after his former wife, JoAnn Wilson, was bludgeoned and shot to death in the garage of her Regina home in 1983.

After he was granted parole in 2006, Thatcher, who is now 70, returned to Saskatchewan to live on his family property near Moose Jaw.

The book also includes a copy of the entire transcript of a police-taped conversation between Thatcher and a man who claimed Thatcher offered him $50,000 to kill Wilson. David said the book allows readers to assess that conversation for themselves.

"In some ways, it's a mystery. As various clues come along, it unfolds. We don't ultimately find out who did it, according to him. We just find out why he didn't do it," David said.

Wilson's younger sister, Nancy Geiger, said she's not surprised the book is coming out.

"Whether it gets classified in the fiction aisles or the non-fiction aisles depends on how people choose to place it and what they think of what he says," Geiger said from her home in Iowa.

Despite reluctance from his children to put the case back in the spotlight, Thatcher wanted to have the book published, said David.

"He really wanted to have his say. He feels that he was unjustly convicted and that people ought to hear his side of the story."