EVERETT — It took longform journalist Edward Humes a few rewrites to find the right way to open his latest book, “The Forever Witness.”

Humes, a Pulitzer Prize winner in 1989, chronicles how a Snohomish County cold case pioneered a new method of solving seemingly unsolvable cases through forensic DNA technology.

Ultimately, the author brings the reader back to November 1987, through vignettes pulled from a rich cast of real-life characters affected by the brutal killings of Canadian couple Jay Cook, 20, and Tanya Van Cuylenborg, 18.

Snohomish County sheriff’s detective Jim Scharf, then a patrol deputy, emerges as a kind of guide for the story’s arc, which parallels the rise of DNA technology in criminal cases.

Meanwhile, the families of Cook and Van Cuylenborg, especially the two fathers of the slain Canadians, offer the “heart” to a book that aims to tell the human side of a true crime drama, while also balancing the clinical scientific angle of how forensic genealogy burst onto the scene. Since 2018, detectives around the country have turned to ancestry databases to crack cases with DNA evidence. This was one of the very earliest examples.

“There was a lot of coverage of this case when it broke,” Humes said in an interview with The Daily Herald, “and I’m sure you remember it was right on the heels of the Golden State Killer case, where it was first time most of us heard this thing called genetic genealogy. I don’t think we…