SAN FRANCISCO (AP) _ For Ken Narlow, watching a re-enactment of the Zodiac killer's handiwork was nearly as disturbing as the crimes themselves.
The former Napa County detective, now 75, served as a consultant in the making of the upcoming motion picture ``Zodiac.'' He says the film, coupled with investigators' recent decision to retest three envelopes for DNA, is rekindling interest in the still-unsolved case.
``It's a case that gets put on the back burner, but you never put it away,'' Narlow said in an interview one day after previewing the film he called ``mesmerizing.''
The Zodiac killer _ he gave himself that moniker in his taunting letters to police and newspapers _ is blamed for at least five slayings in 1968 and 1969. He was never caught, though many, including the author of the book on which the movie is based, believe he was Arthur Leigh Allen, a convicted child molester from Vallejo who died in 1992.
In September 1969, the Zodiac struck in Napa County, stabbing two 20-year-old college students picnicking at Lake Berryessa. The crime scene was a small peninsula jutting out into the lake. The couple were accosted, hog-tied and repeatedly stabbed by a man dressed all in black and wearing a hood.
Cecelia Shepard died; Bryan Hartnell survived and is now a lawyer in Southern California. He did not return calls seeking comment from The Associated Press.
Narlow met the ambulance at the hospital that day, calling what happened to the young couple ``heart-wrenching.''
Thirty-eight years later, he was upset all over again when the stabbings were re-created for the film.
``I can sit through autopsies and gruesome cases,'' he said. ``But it never affected me like it did when I was with the director when they were filming that scene.''
The $80 million film, opening nationwide Friday, is based on the 1986 true-crime book by Robert Graysmith, the former political cartoonist at the San Francisco Chronicle who investigated the case for years as an amateur sleuth.
It was shot in 2005 in the Bay Area and stars Jake Gyllenhaal as Graysmith and Mark Ruffalo as police Inspector David Toschi, who also inspired Clint Eastwood's ``Dirty Harry'' character. It's directed by David Fincher, who made ``Fight Club,'' ``Seven'' and ``Panic Room.''
Graysmith said he was astounded at the lengths to which Fincher went to keep the film historically accurate.
``I've never seen anything like it in my life,'' he said. ``Jake is wearing my clothes. ... Same pad. Same pen. Same bright red VW Rabbit.''
Graysmith and Narlow also are encouraged that police interest in the case has been reinvigorated, although authorities insisted the timing has nothing to do with the movie.
Vallejo Police Lt. Richard Nichelman said Friday that three envelopes from the case had been sent to the state crime lab for DNA retesting. He said he expects results in a few weeks.
``You're obligated to do it if you have new technology,'' he said. ``Percentage-wise, it doesn't look good, but you've got to have hope.''
Three killings took place in the Vallejo area. David Farraday and Betty Lou Jensen, teenagers on their first date, were shot to death in December 1968. Darlene Ferrin, 22, was shot and killed seven months later at the Blue Springs Golf Club, while her companion, Michael Mageau, 19, survived. Graysmith said filmmakers even tracked down Mageau as they grew obsessed with the case.
``They're still calling, asking questions,'' Graysmith said, laughing. ``There is something about this case from the arcane symbols, the unbreakable ciphers. ... And the fact they came so close to catching this guy time and time again.''
While Narlow believes the Zodiac is still at large, Graysmith said he's confident it was Allen, even though an earlier, partial DNA profile from envelopes holding his letters appeared to clear him.
Circumstantial evidence _ a shoe, his presence at Lake Berryessa at the time of the crime and other factors _ points squarely in his direction, Graysmith said.
Toschi, who was unavailable for an interview but attended the preview in San Francisco, also thinks it was Allen, according to Graysmith.
Evidence was removed from Allen's house shortly before he died, Nichelman said, but he refused to elaborate.
``In our hearts we know the Zodiac's reign of terror has ended,'' Graysmith said.