Photo: Justin Sullivan /

Paul Holes, the retired Contra Costa County investigator who led an elaborate effort to track down the man suspected of being the Golden State Killer by using a genealogy site, has hired an agent to negotiate a deal to sell the rights to his story.

Holes, who traced DNA from a crime scene to distant relatives of the suspect, plans to write a book about his work on the case, said his representative, Peter Clemente of XG Productions, a talent management company that specializes in true crime.

Holes recently retired from the Contra Costa County’s district attorney’s office and had been tracking the Golden State Killer — also known as the East Area Rapist, who police say killed 12 people and raped 45 between 1976 and 1986 — for 24 years.

“It was definitely an obsession,” he said in an interview with ABC News last week.

After criminal DNA databases produced no matches to the killer’s DNA, Holes ran it through a publicly accessible genealogy site called GEDmatch, which contains DNA profiles of 960,000 people. The genetic data are uploaded to the site by people who obtain the information from a number of testing companies and want to trace their heritage or find possible relatives. Each profile is connected to a name.

Holes found between 10 and 20 distant relatives, roughly equivalent to third cousins, which he used to trace back to a common ancestor — great-great-great-grandparents from the 1800s, according to the Washington Post. He began filling in the blanks of the family tree using other sources, including a grave site locator, old news clippings and census data. Then he narrowed down the pool of suspects to men around the projected age of the killer who had connections to Sacramento and other California cities where the crimes were committed.

It led to the arrest of Joseph James DeAngelo, 72, on April 24.

The effort is being lauded by some DNA experts as a law enforcement tour de force. But it is also prompting privacy concerns over law enforcement’s access to people’s sensitive genetic information.

Catherine Ho is a San Francisco Chronicle staff writer. Email: cho@sfchronicle.com Twitter: @Cat_Ho