In the scene where Harry Callahan shoots Scorpio in the leg on the football field, as he walks towards him, Scorpio shouts out, "Don't do anything more! No! No!" If you look at his face however, you can see his mouth is not moving to what he is saying.
When Callahan enters the groundskeeper's room, there is an Oakland Raiders pennant hanging on a locker. But Kezar Stadium was the home of the San Francsco 49ers; given the two teams' cross-bay rivalry, it is not likely that the 49ers groundskeeper would allow a Raiders pennant in his locker room, as the Raiders only played there in 1960 and the 49ers played there for a further 10 years (and finished the 1971 season in first place in the NFC west).
The children on the hijacked bus sing "Old MacDonald Had a Farm". Normally somebody would need to lead and say what specific barnyard animal was owned by Old MacDonald. Instead the entire choir picks the same animal in unison and without prompting.
The Chief concludes his mini-lecture on "sick guys" and their "behavior patterns," by mumbling "it must appeal to their super-ego or something." According to fundamental Freudian theory (Psyc 101), the "super-ego" is that part of the human psyche that restrains humans from doing anything that is evil.
When Harry is following Scorpio's instructions to run from phone booth to phone booth, he boards the subway. When he arrives at his destination, it is the exact same station as the one where he boarded.
In the scene where Harry is waiting for the school bus to drive under the bridge, you see Harry crouch as the bus approaches, as if to jump on the roof.
In the next shot, you can see Harry in the reflection of the bus windscreen, actually standing upright.
Before Harry clicks on the empty chamber for the bank robber, you hear and see him pull the hammer back to fire in single-action mode. However, when the camera faces Harry and he actually does pull the trigger, it is in double action, indicated by the fact that you see the cylinder spin again.
When Scorpio pays a man to beat him up, there is a moment when the man wishes to stop the beating. We see Scorpio's face, and he is severely disfigured. The man hits him a few more times and then the beating ends. When he arrives in hospital, Scorpio's entire face is in bandages. However, only a few weeks later, Scorpio is released from hospital with only a small plaster across the bridge of his nose. The severity of the injuries seen when he is getting beaten would not have dissipated in only a few weeks, indeed, they would almost certainly lead to permanent disfigurement, yet other than the plaster, Scorpio appears unblemished.
In the opening scene, Scorpio is tracking the swimming girl through his scope, which provide the POV for the camera. As he shoots, the cross hairs are removed and the camera shows the girl from the same angle. However, when the girl is hit, the bullet hole is below the right shoulder and as such has to be from a bullet fired from at least 90 degrees to the right of the camera, there is no way Scorpio could have hit her where he hit from his supposed position on the other building.
In the scene where Harry is preparing to deliver the ransom money to Scorpio, he tapes a switchblade knife to his leg. The knife is positioned with the bolster or tip pointing upward. In the later scene at the cross, Harry pulls up his pant leg and exposes the knife - it is clearly pointing downward, the opposite of the way he taped it earlier.
The white pillarless sedan seen during the bank robbery scene (not the getaway car - which is a 1966 Ford Galaxie 500) changes from a 1970 Ford Galaxie to a Torino (where Harry walks up to the bank robber where he does the famous line of 'six shots or only five').
As Harry crosses the street toward the downed bank robber, the shotgun is a few feet away from the robber's hand and well out of reach. A moment later after Harry delivers his famous lines, the shotgun is only a few inches away from the robber's hand, making it clear why the robber was tempted to go for the weapon.
Near the end of the movie, Scorpio directs the mayor to provide an airplane for his escape at Santa Rosa airport. When he hijacks the bus, he directs the bus driver to exit the 101 northbound at Sir Francis Drake Blvd - which makes no sense, as Santa Rosa Airport is some 50 miles north of Sir Francis Drake Boulevard.
The District Attorney tells Harry that his search of Scorpio's dwelling was illegal and violated the Fourth Amendment, making all evidence inadmissible. Harry's search is entirely legal under Exigent Circumstances, as someone's life was in imminent danger. Additionally, Scorpio is stated to be living in Kezar Stadium under the consent of the grounds-keeper. However, the grounds-keeper, in all likelihood, does not have the legal standing to grant that kind of permission, making Scorpio a squatter and thus not protected by the Fourth Amendment.
Some considerable time after the first shooting, the police have arrived and Callaghan has climbed up to the roof from where the shooting took place. Yet when he looks down to the rooftop swimming pool, the blood in the pool is still only in one small area, instead of having been dispersed in the water.
In the opening scene, Scorpio is shown using a high-powered rifle with a silencer. When he fires, the sound is muffled, as with a silencer. The silencer used as a prop is for a small caliber pistol. Not only wouldn't it silence a rifle, the gas pressure would probably blow it apart. Also, while it would be possible to suppress the muzzle report with a proper silencer (about a foot long and 3" diameter for that rifle), the distances involved would still require a supersonic bullet, which causes a supersonic crack. The suppressor would make it harder to identify the source and direction of the shot, and harder for civilians to identify the nature of the sound, but it would still be an audible crack.
Besides the Sir Francis Drake/San Quentin exit being nowhere near the Santa Rosa airport, even in the 21st century Santa Rosa has only 5,000-foot runways, inadequate for most of the period jetliners to use.
As powerful as the 44 Magnum round is, it cannot and will not knock a person backwards as it strikes them. Not even the .500 Smith And Wesson Magnum will do it either. If the 44 Magnum (or any other magnum handgun round) could knock a person backwards, the shooter also would be knocked backwards per Newton's Third Law of Motion.
When Scorpio is baited to come after the priest, Harry is wielding a Winchester Model 70 in .458 Winchester Magnum. In the ensuing shootout, Harry fires 6 rounds without reloading. In reality, the size of the .458 Win Mag case is so large that it limits the magazine capacity to 3 (2 in some rifles). With one round in the chamber, the maximum number of rounds he could have fired without reloading is four.
The killer is quickly identified as using a 30.06 rifle, one of the most powerful in the world with an effective range up to 3,500 yards, having a muzzle velocity of about 2,700 feet-per-second and over 2,400 foot-pounds of force. In the first scene, the killer is only 300 yards from his target, and from that distance, the bullet (150-grain) would have traveled completely through the woman's body and kept going, and not just stopped after hitting her scapula (shoulder blade bone).
When the Police helicopter spots Scorpio on the rooftop, the Police Office calls for him to halt. Although we see the officer use a microphone in the cockpit, there is no blow-horn or other speaker mounted on the aircraft to direct the sound.
It is often claimed that Harry is incorrect when he refers to the .44 Magnum as the most powerful handgun in the world. Technically, he is and he isn't. In 1971, the .44 Magnum (developed in 1957) was the most powerful commercially available handgun in the world, meaning it fired the most powerful production cartridge. This means it was the most powerful handgun round made by ammo companies and sold on the market. In 1971, the .454 Casull (developed in 1959) was more powerful than the .44 Magnum, but the .454 Casull wasn't produced commercially until 1983, so Harry is inaccurate in stating that it is the most powerful handgun in the world, but he is accurate in stating that it is the most powerful handgun available for use.
Harry Callahan is referred to several times as Inspector 71 but when we see his badge at the end of the film it clearly says Inspector 2211. However, many police departments have set radio IDs for certain positions (e.g. Homicide detectives), and these have nothing to do with the badge number of the person filling that role.
At the end of the bank robbery Harry delivers his famous line which includes "Did I fire 5 times or 6"? Some viewers have suggested that Harry fired only 4 times, but in actuality you only see Harry fire 4 times - if you listen carefully you hear 6 shots.
After Scorpio takes the school bus, in the pan across the Civic Center there is a Texas flag flying outside of the mayor's office. However, the Civic Center Plaza has all fifty state flags on display - the Ohio flag can also be seen momentarily.
When Callahan is playing Scorpio's game of running around different locations, Scorpio tells him not to talk to anybody or the girl dies. As Callahan is approaching his final destination at the cross, he tells Chico via wiretap that he sees a couple necking. However, it is possible that Scorpio didn't see this incident, as he couldn't have been watching Harry at this moment in time.
Scorpio is not charged with any crime, due to lack of evidences. However, in reality, he could have been charged with assault on an on-duty police officer (when Harry is hit on the head as he's trying to deliver the money), assault with intent to kill (when he fires at Chico), and illegal possession of an automatic weapon.
When the Ford sedan at the bank robbery hits the flower stand and fire hydrant you can see the smoke from the "log cannon" used to flip the car coming out from underneath. Then, in an overhead shot, the wire coming from the trunk used to set off the charge is visible running off screen left.
At the cross on Mount Davidson, Scorpio makes Harry toss his gun a good distance away onto concrete, which would cause noticeable damage to the revolver's blued finish. However, in the final scene (when Harry again delivers his famous speech,) there is no visible damage to the weapon.
During Harry's visit to the Mayor's office, cable car bells are heard ringing intermittently. This particular sound would, in reality, be inaudible since the cable car routes don't pass anywhere near City Hall. Closest routes on California and Powell streets are several blocks away.
In the famous pull-back shot at the football stadium, as Harry stands on Scorpio's leg, the wind caused by the rotor blades can clearly be seen. In the previous shot, Harry's jacket is motionless, but when it cuts to the helicopter shot, his jacket is blowing back and forth.
When Callahan is conducting his stakeout from the roof of a downtown building he is armed with a rifle chambered in.458 Winchester. This is an "express" type cartridge manufactured specifically for the hunting of thick-skinned, dangerous African game such as elephants. Like all cartridges of this class it fires a massive projectile, which, due to its weight, drops very quickly over short distances and is meant to be used at relatively close ranges. It is the LAST type of cartridge that any knowledgeable shooter would employ in a sniper role.
There are numerous contradictions and inconsistencies with San Francisco Police Department polices on tailing suspects, correct radio procedures and etiquette, calling in their position, calling for backup, and unlawfully discharging their firearm (e.g., the police fire their guns into the air as warning shots).