It appears there is some confusion over the rank of the Special Branch officer played by Tony Britton. In the film's dialog he is called Chief Superintendent Thomas by Mallison and other characters in the British segment, but is Called Inspector Thomas in the end titles.
During the Mass scene at the cathedral, the priest is seen standing behind the altar facing the congregation. At the time the movie portrays (1963), the priest would have his back to the congregation. The change in the mass was one result of the Church's Vatican II council in 1968.
When the dispatch-rider arrives at the Ministry of the Interior, there's a new type Citroen ID/DS parked in the courtyard: the version with the double headlights that wasn't introduced until the late sixties.
In the first minutes of the movie the man on the scooter turns right and passes a Peugeot 504 parked on the corner, this car came on the market only in 1969. The Renault 16, available from 1965, can be seen in different scenes of the movie. In the section of the movie where the Jackal makes his preparations for the assassination in Paris you can clearly see one passing the café on the Place de Rennes from where he observes the concierge.
While discussing Charles Calthrop's possible involvement in the 1961 assassination of General Trujillo, the British detectives refer to the latter as dictator of Dominica. Trujillo was in fact dictator of the Dominican Republic, a different nation in the Carribean. (In a later scene where Calthrop's passport is shown, we see the visa stamp for "Republica Dominicana", Spanish for Dominican Republic.)
When Lebel is advised by telephone that the Jackal has passed through the border into France in his white Alfa Romeo, he is told the license plate number is GE 1741 when, in fact, the license plate number on the Jackal's car is GE16 1741.
At the hotel The Jackal checks the guest book to find out Clare's room number. Each guest has a date of birth next to their name, Clare's being August 1933, which would have made her 30 at the time the film was set (1963), however, her character is supposed to be around 40 and has a 19-year-old son.
In the shooting at the Petit Clamart ambush the lower part of the rear window of the presidential limousine is shattered and falls to pieces, but when the car arrives at the airport the rear window, though badly cracked, is still largely in place.
As the Jackal is presenting his identification to the policeman near end of the movie, we see numerous people walking to what is supposed to be a controlled area. When the Jackal is allowed to pass, the camera angle changes shows the area where the people were walking devoid of people other than soldiers.
When the Jackal tests and calibrates his new rifle in the forest, the telescopic sight on the weapon changes from one model to another - in some scenes, the two calibrating screws on the sight are small and silver, in others - they're large and reddish.
When the Jackal first is trying to get a target on the president, the shot is taken outside the building and you can clearly see rain pouring down the roof tiles. Next shot shows the president and the crowd all dry with no sight of rain anywhere.
When the Jackal parks the blue car (he had stolen from Madame DE Montpelier) between two others vehicles there is absolutely no space for him to move out from the drivers seat. But in the next shot we find him easily maneuvering himself out.
When the Brits find the bogus passport application it's reported as having been applied for on July 14th and mailed on the 17th. Later when Lebel is announcing the find he says that that the passport was issued on July 30th.
The amount of gray in Lebel's hair changes noticeably in different scenes, beyond what lighting conditions would account for. Much grayer for some reports given in the conference room, distinctly less so in other settings.
When the Jackal is picking up his sniper rifle, the gunsmith takes out a box of ammunition. He says that he took out six bullets to make them explosive. The box in the background has seven bullets missing.
When we first see the Jackal at the market in his Alfa Romeo, the license plate reads GE16 1741, with no space between the GE and 16. Every shot after that of the license plate has a very noticeable space between the GE and 16.
In the opening scenes, as the ministers are leaving the palace, the camera angle from inside, looking out, sees a French flag flying briskly in a continuous breeze. In the very next shot, taken from an aerial perspective looking back towards the departing ministers, the flag is hanging limp and there is no breeze.
When the Jackal prepares to take his final shot at the melon in the forest, he is clearly shooting with the rifle on his right shoulder, but he views the sight with his left eye. No sniper could see reasonably through the sight with his opposite eye, which turns his head away from the intended line of fire.
Rafael Leonidas Trujillo is identified as dictator of Dominica. Not only is that a confusion with the Dominican Republic, but Dominica was not even independent in 1963; its independence would come on 3 November 1978.
When Wolenski gets the mail from the post office, the narrator says the mail is addressed to General Delivery. But Wolenski is shown opening a P.O. Box; General Delivery mail is held at the counter and called for by name.
When the Jackal releases his leg while posing as the old man, he is only wearing a sock on that foot. Later, while he waits for De Gaulle, he is wearing shoes on both feet. However, it's possible he stole a pair of shoes from the apartment while waiting.
It is sometimes claimed that The Jackal hides the pieces of his disassembled rifle in his car's exhaust pipe, which would prevent the engine running. The pipe in question is fat and corrugated, not slim and smooth like an exhaust pipe.
The Jackal is supposed to be one of only three guests who
checked in at the hotel that day. Supposedly Clare is one of the other two guests, since she tells the Jackal that she had spent the day attending her son's graduation ceremony at his school in the Alps. That means the Jackal's alias ("Duggan") must be entered on the first or second line above or below Clare's name in the guest book. "Duggan" is not entered anywhere near Clare's name in the guest book. Also, more than two names are entered below Clare's name (on the same page as well as on the next page of the guest book), which means there were more than three guests who checked in that day.
When the Jackal enters the final apartment to carry out the attempted assassination, he uses a key, taken from the lobby, to open the apartment door. When he has entered, he does not re-lock the door with the same key, but turns a dead lock, which is higher up the door, to secure it. However, when the policeman, with Lebel, shoots the lock, to burst open the door, he fires at the lower lock. The door falls open, yet no shots were fired at the upper lock, which is securing the door.
The goof items below may give away important plot points.
The very last frame of the very last scene - just as the production credits begin to roll - the grave digger abruptly checks the toss of a spadeful of dirt into the open grave; obviously 'cut' was called but the final edit ran a bit past.