Dave Toschi was, like Dirty Harry, an inspector in the San Francisco Police Department and, strangely, Dirty Harry wasn't the first--or last--time somebody would work him into a movie. The flamboyant-even-for-San-Francisco cop would serve as the inspiration for 1968's Bullitt, in which the main character (Steve McQueen's Frank Bullitt) was based on Toschi, complete with an upside-down quick-draw shoulder holster.
It was actually in the couple of years after Bullitt when Toschi would gain nationwide fame as one of the investigators tracking down the real-life Zodiac killer. For the second time, Toschi made such an impression that a Hollywood writer ran home and tried to work him into a screenplay.
Thus, in 1971, Toschi would see another fictionalized version of himself on the silver screen, in the form of Dirty Harry, where Harry hunts down the "Scorpio" killer. The difference being that while the Zodiac case never got solved, Dirty Harry finds Scorpio and kills his fucking ass.