Trivia: When Harry chases down Scorpio, who has kidnapped a busload of school children, the character has to leap from a trestle bridge on to the top of moving bus. If you watch the scene carefully, you will notice that it is not a stunt man making the jump - Clint Eastwood (Harry) performed it himself.
Trivia: Dirty Harry's .44 Magnum was not the most powerful handgun in the world at the time. In fact, among firearms enthusiasts (such as screenwriter John Milius, an NRA Board Member), there were a few relatively-well-known examples of pistols that were more powerful. Perhaps best-known was that R.B. Rhodda & Co. of Calcutta had sold a number of side-by-side pistols in .303 British during the 1890's through the 1920's. The .303 is a relatively potent rifle caliber that is significantly more powerful than the .44 Magnum. With that said, I can certainly understand why an SFPD officer wouldn't be lugging around an unwieldy, side-by-side, two-shot pistol.
Trivia: Dirty Harry is reputed to be the film that significantly launched Clint Eastwood's film career and was released in 1971. Also released in 1971 was Play Misty For Me, which was Clint's directing debut. In this film, when Clint walks into the diner just before the bank robbery, the cinema on the right hand side of the shot is advertising Clint's other movie Play Misty For Me.
Trivia: Scorpio's real name is never revealed throughout the entire movie, and in the ending credits he is simply listed as "killer".
Trivia: Andy Robinson (Scorpio) received several death threats after the film's release and had to get an unlisted phone number.
Trivia: The young boy who Scorpio grabs at the pond towards the end of the film is Andy Robinson's real-life stepson, Steve Zachs.
Trivia: In real-life, Andy Robinson (Scorpio) is a pacifist who dislikes guns. Every time he fired a gun during the early stages of principal photography, he would flinch violently, so director Don Siegel was forced to close down production for a time and send Robinson to a school where he would learn to fire a gun convincingly. In spite of this, he still blinks when he shoots.
Trivia: When Harry shows Scorpio his gun for the first time, Scorpio says "My, that's a big one." Andy Robinson (Scorpio) ad-libbed this line. The crew broke up laughing, which resulted in the scene being re-shot. The ad-libbed line remained in the film.
Trivia: Director Don Siegel has a cameo role in this film - he is the pedestrian walking past Harry's car when he and Chico return to the police headquarters.
Trivia: After Harry has finally killed Scorpio, he takes out his police badge and tosses it into the nearby water. Clint Eastwood was initially very uneasy about doing this because he feared it would mean to the audience that Harry was quitting police work for good. Director Don Siegel argued that Callahan was simply irritated with the policing system that made it difficult to dispatch of the killer in the first place, but decided to co-operate with Eastwood and tell him that he could simply draw back his arm before thinking twice and putting it back in his pocket. Eventually Eastwood changed his mind and threw the badge into the water.
Trivia: The original title of the movie was "Dead Right".
Trivia: The character of "Scorpio" was loosely based on the real-life "Zodiac Killer", who had committed five murders in the San Francisco Bay Area several years earlier.
Trivia: Scorpio has no dialogue until 46 minutes into the film.