In David Fincher’s Zodiac, a notorious killer inspires obsession and self-destruction

The director spent 18 months conducting his own investigation. As Clarisse Loughrey writes, the lines between subject and artist soon became blurred

Robert Downey Jr plays crime reporter Paul Avery, one of the key figures in the Zodiac case (Rex)

Two lovers idle away an afternoon on the shores of Lake Berryessa, in Napa County. It’s 27 September 1969 – Cecelia Shepard and Bryan Hartnell plan to soon part ways and head off to different colleges. This place offers them a momentary haven, shaded by a few oak trees. A man approaches. With each step, the details become clearer: a black executioner-style hood and clip-on sunglasses, alongside a bib of sorts, marked by a white circle and cross, like the sights on a gun.

Shepard and Hartnell were the fifth and sixth confirmed victims of the Zodiac Killer. He’s believed to have targeted seven individuals in total, though – in his taunting letters to the press – he claimed to have killed 37. The couple at Lake Berryessa were stabbed repeatedly. Shepard lapsed into a coma and died. Hartnell survived. Despite numerous suspects, the Zodiac Killer was never caught. There are those who believe he’s still alive today.

David Fincher’s Zodiac, released in 2007 and dramatising the decades-long manhunt, restages his crimes with forensic accuracy. The oak trees at Lake Berryessa were no longer there, so the director insisted two new ones were helicoptered in, with just enough water to keep them alive for the duration of the shoot. Costumes were carefully reconstructed from evidence photos and testimonies.

For the murder of cab driver Paul Stine on 11 October 1969, Fincher tried to return to the scene of the crime – the intersection of Washington and Cherry, in San Francisco. Residents felt uneasy about the prospect. Having failed to secure permission for the shoot, the director instead opted to have the neighbourhood painstakingly recreated using CGI. To ensure the right mood, he bathed his entire film in a sickly, yellow glow. Not only does it befit the smoke-choked hideouts of the Seventies working man, but it makes every location feel harsh and comfortless. There’s no safety to be found at home. And the night? It’s such an inky black, it threatens to consume all who pass through it.

Fincher, screenwriter James Vanderbilt, and producer Bradley J Fischer spent 18 months conducting their own investigation into the murders. The trio pored over police transcripts and met with the two surviving victims: Hartnell and Mike Mageau, who was shot in a parking lot alongside Darlene Elizabeth Ferrin on 4 July 1969. They even acquired the services of a linguistic expert, in the hope they could provide some new insight into the Zodiac’s bizarre dispatches. Of the four cryptograms he sent, only one has been solved – not by the FBI or military-trained cryptographers, but by high school teacher Donald Harden and his wife Bettye.

The line between artist and subject had blurred, as the trio became as obsessed with the case as those whose stories they set out to tell. Zodiac isn’t the portrait of a killer, per se, but of the men who were consumed by their desire for the truth. Vanderbilt’s screenplay draws heavily from the writings of Robert Graysmith. Played by a plucky and inquisitive Jake Gyllenhaal, he becomes the film’s closest thing to a protagonist.

At the time of the murders, Graysmith worked as a political cartoonist for the San Francisco Chronicle. Vanderbilt plots out how his amateur interest in the Zodiac’s ciphers found him drawn into the lives of three key figures: crime reporter Paul Avery (Robert Downey Jr, in one of the best displays of his erratic charm), Inspector David Toschi (Mark Ruffalo), and his partner William Armstrong (Anthony Edwards). All four of them slowly start to lose themselves to the case. This is a film about slow decay – we see their bodies crumple, their faces grow hollow. Addiction rears its head. Families break apart. “When you talk about obsession, you have to talk about the toll,” Fincher told the LA Times. “Toll is not something you can explain. It’s something you have to feel.”

Arthur Leigh Allen (John Carroll Lynch, formidably unnerving) fits the profile. He’s a convicted a paedophile whose own relatives are convinced he’s the Zodiac Killer – both misspell the same words and share a shoe size. His navy background would also account for the cryptograms. But the case would never stand up in court. As hard as these men try to pin it on Allen, their efforts inevitably go to waste. “I can’t tell if I wanted it so bad because I thought it was him or wanted it to be over,” Toschi later admits. Fincher saves one final, cruel twist for the film’s epilogue: 20 years later, Mageau picks Allen’s photo out of a line-up – this, he says, was the man who shot him. Before police can bring Allen in for questioning, he dies of a heart attack.

Zodiac exists in a very different world to 1971’s Dirty Harry, which took inspiration from the case but sees its version of Toschi, Clint Eastwood’s Harry Callahan, ditch the judicial process and shoot the killer point-blank. That didn’t make Fincher’s film popular with everyone. Most reviews were positive, but detractors were often unnerved by the film’s inconclusiveness – The Washington Post called it “largely without drama”. It earned only $33m at the North American box office and failed to land a single Oscar nomination.

Fincher may be a wildly cynical filmmaker but, with Zodiac, he makes an intriguing point: are these men committed to the pursuit of justice or are they after a more personal sense of resolution? Graysmith’s story ends when he goes to Allen’s workplace, so he can look eye-to-eye with the man he believes in his heart is guilty. He may not be able to convince a court, but he can convince himself – that, in itself, may be enough to feel like the world hasn’t spun out of his control.