‘Dirty Harry’ Was Influenced by the Zodiac Killer and the Cop Who Spent His Life Searching For Him

The Zodiac Killer has never been captured nor charged for his crimes, but his reign of terror and the ongoing mystery surrounding his identity has left a lasting imprint on the world of true crime. 

From the late 1960s to the early 1970s, the serial murderer took the lives of at least five victims throughout the state of California, although he may have killed as many as 37. He frequently targeted young couples in quiet or isolated areas, often choosing to shoot them with a .22 caliber pistol. 

As authorities tried to piece together the string of seemingly random murders, investigators uncovered twisted clues left behind, including items belonging to the Zodiac Killer’s previous victims and his signature symbol: two crossed lines inside a circle.

All the while, he taunted authorities with more than 20 written letters and cryptograms mailed to local newspapers and investigators. Among his communications were several ciphers, a series of coded messages that included clues to his identity and threats about future crimes. With every letter, the killer insisted his messages be published on the front pages of newspapers, promising to unleash even more terror if his demands weren’t met. 

Over the course of several years, letters from the Zodiac Killer continued to pour in, making him a media sensation. He even alerted authorities to his own crimes in a series of phone calls. With Californians on high alert, citizens were never sure where he would strike next—until it all seemingly came to a stop around 1970. 

As a new decade unfolded, notes claiming to be from the killer started to slow down. To this day, it’s unknown if correspondence and murders that happened after that period can be ascribed to the killer. There’s been no confirmed communication from him since 1974.

Investigators dedicated their lives to uncovering the Zodiac Killer’s identity, and while there have been several suspects, there has never been enough evidence to make arrests. The case remains open and is under investigation by California authorities and the FBI.

Just following the peak of the Zodiac Killer’s crime spree, Clint Eastwood signed on to star in 1971’s Dirty Harry, which would become the first of four movies following a vigilante cop in San Francisco. The action-packed thriller chronicles Harry Callahan’s unconventional methods to capture killers and criminals with his .44 Magnum and little regard for civil rights and due process. 

The first film in the series was heavily influenced by the Zodiac Killer, beginning with the movie’s Northern California setting and the antagonist’s pseudonym, Scorpio, a clear allusion to the zodiac calendar. Much like the real-life killer, Scorpio sporadically targets innocent victims and  leaves behind notes. Spoiler alert: As Callahan gets closer to capturing the killer, Scorpio even hijacks a school bus, a reference to the Zodiac Killer’s own threat to shoot children on a school bus, a plan that thankfully never came to fruition. 

Callahan is said to be based on real-life San Francisco Police Department officer Dave Toschi, who spent almost a decade trying to uncover the identity of the Zodiac Killer, a mystery he was never able to completely solve.

Toschi began his career in the military, serving in the U.S. Army during the Korean War, per the Los Angeles Times. In 1953, he joined the police force in San Francisco, and by 1969 he had been brought on to the team investigating the Zodiac Killer. 

Much like Callahan, Toschi was known for his charismatic personality and eclectic suits. He spent years conducting thousands of interviews and examining evidence to uncover the identity of the Zodiac Killer. While he did not share the same notes of moral ambiguity as Callahan, Toschi demonstrated the same dedication to discovering the truth. Unlike Callahan, he respected the law and did not pursue his prime suspect with a similar law-bending approach to the fictional character. 

During his career, Toschi came close to solving the mystery of the Zodiac Killer but unfortunately never had enough evidence to make an arrest. 

In addition to his influence on Dirty Harry, Toschi also inspired Steve McQueen’s character, detective Frank Bullitt, in the 1968 film Bullitt. While Toschi had no part in Dirty Harry, he was actually interviewed by McQueen prior to his work on the movie.

“Steve McQueen was a lovely guy,” Toschi told the Daily Mail in 2014. “He came to homicide for inspiration while he was filming. He seemed to take to me. He liked the way I wore my holster upside down and put my raincoat over my shoulder.”

Toschi was later portrayed by Mark Ruffalo in the 2007 film Zodiac and served as a technical advisor on the film. 

While Toschi never publicly revealed how he felt about Dirty Harry, viewers receive some possible insight into Toschi’s reaction thanks to a scene in Zodiac. His onscreen character attends a showing of the movie. Visibly frustrated by what is going on in the film, Toschi heads to the lobby to smoke a cigarette.

As other attendees leave the theater, one says to Toschi’s character, “Dave, that Harry Callahan did a hell of a job with your case,” to which he sarcastically responds, “Yeah, no need for due process, right?”'