The narrator mentions they arrive back in San Francisco in early October, but in the document (prepared by Grisby) that Michael signs verifying his killing of Grisby, it is dated August 9th, supposedly the next day.
Elsa enters the hall of mirrors wearing a pair of peep-toe heels with a distinctive crisscross ankle strap, but a later shot in the same scene shows her wearing plain pumps with no ankle strap. Seconds later, she's wearing the original ankle-strap heels again.
In the courtroom scene, Mrs Bannister's maid is sitting behind her when she is called to testify, but in the next shot, when she gets up, there is a man sitting there.
Rita dives off the cliffs. However, in the following scene as she boards the boat her hair is dry.
The break on the driver's side of the windshield of Grisby's car vanishes.
When Mrs. Bannister purchases her ticket at the box office of the Chinese theater, the girl says "konnichiwa," which is a Japanese greeting.
While the jury is deliberating, O'Hara and the Bannisters are sitting in the otherwise empty courtroom. It would have been standard procedure for O'Hara to be taken back to his jail cell.
After being called to the stand as a prosecution witness, Bannister says he will cross-examine himself. The prosecutor angrily denounces this as a cheap trick. In fact, this is standard procedure in such cases.
When Michael and Arthur Bannister are talking in court, the court officer comes over to them and informs them that the jury has reached a decision. They stand as the judge and jurors enter. They then sit down before the jurors have taken their seats. This procedure is incorrect. Before a judge enters, the bailiff announces the judge's entrance by asking all to rise, and they stay standing until the judge says be seated.
When Mrs. Bannister is lunging for the exit in the mirrored room, the "broken glass" in the foreground stays in frame as the camera pans to the right, spoiling the illusion of a cracked window. But this was intentional. The filmmakers superimposed still images of bullet-riddled glass over several of the scenes during the mirror-room shootout. It was never meant as an illusion of a particular window or mirror being broken, but as an indication of a lot of bullets flying and broken glass.
When Michael is escaping from the courtroom to Chinatown, a cola billboard advertisement featuring Rita Hayworth is partially visible.
During the cuts shown following the trial, there are various scenic shots of the bay area and the bridge in the background. However, everything in the background is perfectly still. There are no waves, the ships are not moving, there is no traffic movement, no pedestrians, and there is no smoke coming out of the chimneys. Obviously the background shots are photos or paintings.
When Grisby and Michael are walking up the hill in Acapulco, in the background, there is a two-story house with a deck on a hill across the lake that is shown above Michael's head. On the next cut, which is a closeup of Michael, the house is now below him. It is obvious that on the second shot, a rear projection screen is being used.
In the Crazy House, Mrs. Bannister's lips do not match the line "we could have gone off together."
After arriving in San Francisco, Michael and Mrs. Banister are discussing whether or not they would be happy with $5000. As the camera switches between the two characters, the shadows of the camera and cameraman can be seen.
When Michael is beating him up, the guard never calls for help, though there are other guards and many other people nearby. Throughout the fight, which results in windows being broken and furniture overturned and smashed, no one is attracted by all the noise.
Grisby wants to kill Mr. Bannister and frame Michael for it, but the document signed by Michael specifically admits to a murder on Grisby. If all had gone as Grisby had planned, the document would have been useless.
When Michael swallows a handful of pills, there is an immediate and simultaneous panicky outburst by the entire courtroom over the possibility that he may have overdosed. The problem is that there is no way that all these people in the court room, especially the people behind Michael, could have seen him take the pills and instantly be aware what was going on. In addition, there was no one near him before he took them, but as soon as he takes them, the court officers and the prosecutor are right on top of him.
When Elsa asks Michael why George wanted to disappear, Michael says that George told him he wanted to get away from his wife (a motive that is emphasized in the novel on which the movie is based). However, when George talks to Michael about the disappearance he never mentions a wife, and they had no opportunity to have another talk.
Elsa spent time in Shanghai, which has its own dialect, but in Chinatown she switches between Mandarin and Cantonese.
When the policeman finds a gun in Michael's car, he picks it up in his bare hand and then holds it in both hands to examine it, as if he had never heard of fingerprints.
When Grisby approaches the Bannister yacht, he is in a small motor boat. The motor is used the entire time right up to when it reaches the yacht. But when he leaves the yacht and climbs back into the boat, for no explicable reason, he uses the oars to row away instead of the motor. Oars come in handy if the motor runs out of fuel or breaks down, but on a following cut after Michael and Elsa kiss, Grisby is now using the motor again.
When the shootout in the hall of mirrors ends, there is a closeup of Michael's right hand with a gunshot wound as he turns on the light; then after exiting, he is holding the the right arm on which he has the wound. On the following cut, as he leaves the amusement park, he is walking as if the wound is on the left arm.
The prosecuting attorney, during the trial, says that Michael's bag was packed and he was clearly ready to leave. In the novel, the protagonist is a live-in chauffeur, so the fact that he was planning to leave his job is significant. In the movie, however, he is a sailor who has worked for his employer during a cruise, which has finished, so he would in any case be on his way.