The U.S. Army sergeant demonstrating the M72 Light Anti-Tank Weapon stated that the projectile can penetrate armor plating up to 3/4 of an inch. M72 warheads, in real life, can penetrate up to five inches of armor plating.
At the autopsy of the elderly security guard, the medical examiner says that the killer put his hand over the guard's mouth before stabbing him in the back, but as shown in the earlier scene the killer clearly didn't do this.
When Harry finds the old ladies in the sex parlour they are copywriting a message on a board. Everything is in broken English except the perfectly placed possessive apostrophe in "customers' items" at the end of the message.
When Harry and his old partner are driving to the liquor store holdup, in the shot from the rear of the car through the windshield, Harry's partner is hanging on to the light with his left hand. In the very next shot, he is speaking on the radio with the same hand.
When the Mayor is being kidnapped, while being carried away his vest is clearly unbuttoned (at approx. 1:10:25). The next cut scene, while still being carried away, the Mayor's vest is clearly back to being buttoned up (at approx. 1:10:33).
The mayor's limo screeches to a halt next to a truck and the baddies blow the truck to bits with their rocket launcher. In both long shots of the truck it is clearly not moving, but in the very brief head-on shot of the truck as the rocket hits its radiator, it is slowly moving forward.
Right before the Mayor is kidnapped, the militants shoot a rocket at a semi tractor/trailer which is in front of the Mayor's limo. The cab explodes and catches fire and the driver (or a dummy) can clearly be seen falling out of his seat, head first, towards the pavement. He is not moving so he is either dead or unconscious. The militants then go tazer the Mayor and drag him past the burning semi. Even though less than a minute has passed, there is no sign of the driver's body next to the truck.
At the beginning of the film, before Harry goes into the restaurant, he drives by a lone red car parked at the corner. In the next shot, there is a white car, behind the red car, that wasn't in the first shot.
As the Police vehicles arrive at the Mustafa bust, the third squad car to arrive, number 167 blocks the intersection and its sole occupant gets out however moments later car 167 is seen again at the front of shot pulling up outside Mustafa's premises with a number of armed SWAT officers in it.
When the thieves are entering the warehouse, Mickey's turtleneck collar is folded down. After the guard is killed, you can see her standing inside the truck, and her collar is turned up. In the next shot, and for the rest of the scene it is folded down again.
During the training session with the M72 LAW Rocket, Inspector Moore never would have been allowed to step behind the rocket tube, thus exposing her to the back-blast. Range Safety Officers would have made the area clear before allowing the operator to fire the rocket.
In the raid on Mustafa's hangout we see both SWAT and the regular officers with assault rifles. Regular police officers did not carry high powered rifles until after the North Hollywood shootout at the botched bank robbery in 1997. However, SFPD did not have a full time SWAT team then. Regular officers would carry the their SWAT gear in the patrol cars and deploy as needed. It is possible that the officers in regular uniforms could have been SWAT team members deploying from their patrol duties.
After the first bomb has detonated, when Officer (now Inspector) Moore tells Callahan she's spotted Henry Lee Caldwell leaving the courthouse, and they give chase, Harry jumps through a glass booth-this is in fact a metal detecting booth. If these were in use, how did Caldwell get the explosive device into the courthouse (and get the second one out) without setting off the metal detector?
Early in the film the girl lures the two gas company workers to her home, where the bad guy kills the two men and keeps their truck for use in their heist. Later on, when investigating the heist, the cops finally figure out that the ruse must have been via a gas company truck and uniforms. There is no mention of why the gas company had not reported the disappearance of their two men nor their truck, a full two days earlier.
Early in the film the girl lures the two gas company workers to her home, where the bad guy kills the two men and keeps their truck for use in their heist. Later on, when investigating the heist, the cops finally figure out that the ruse must have been via a gas company truck and uniforms. There is no mention of why the gas company had not reported the disappearance of their two men nor their truck, even though the men's bodies were discovered "last week".
When Harry confronts the priest in his church (shortly before Harry's partner shoots the alleged "nun"), Harry pushes the priest forcefully backwards into the confessional. When the priest hits the 'tiled' rear wall, you can see it shake, revealing it to be a cardboard prop.
When Callahan fires the bazooka at the watch tower that Bobby Maxwell has just climbed up to, the cabin on top of the tower vanishes shortly before the missile hits it. We just see the bare platform for a few frames, then there's an explosion and then we see the platform in flames.
Early in the movie when Harry is about to drive into the liquor store window you hear the sound of racking a pump action shotgun. It then shows one of the robbers with a double barrel shotgun. As double barrels don't have a pump, the famous racking sound would not be possible.