In the opening scene, Adam Thompson (Will Wright) tests a security camera, set to take a picture of anyone opening his wall safe, by opening the safe himself. At the time, he is wearing a gray tweed suit with a striped shirt. However, in the resulting picture, he is wearing a solid black suit and a plain white shirt.
The photo taken of Adam Thompson opening the safe is obviously a posed photograph and does not include the safe.
When Adam Thompson (Will Wright) enters the office, he pauses in the doorway after he hears a noise from another room. He's facing the direction of the noise and about to speak. When the scene cuts to a close-up, he's two or three steps into the office and facing away from the direction of the noise.
Incorrect amount written on the check the prosecutor shows Lt. Tragg on the stand.
Lt. Tragg is questioning Perry Mason outside Frank Jarrett's garage as Jarrett's body is being removed from his car. Tragg extends his left hand and touches Perry's jacket, holding it there. In the back-and-forth shots during the questioning, Tragg is shown withdrawing his hand and refolding his arms. The very next shot is of Perry with Tragg again touching his jacket exactly as before.
Jarrett's dead body is removed from his car and is taken away on a gurney lying flat on his back. Jarret died in his car in a seated position, rigor mortis would have stiffened his body in a seated position. The body on the gurney should be in a seated position, not flat on its back.
When Adam develops the film from the camera in the safe, the film is blank, the story line indicating that no one had entered the safe the night before. The negative should have had Adam's photo on it, as it would have taken his picture when he went to get the negative out to develop. Addition: There is no reason the camera would take a picture when Adam removes the film.
On the stand, the killer says that she lifted the dead Jarrett into the car. Jarrett appears far too heavy for the killer to have had that ability.
Harry Thompson borrows $10,000 from Jarrett and receives a check drawn on the J&L Construction company authorized by Norman Durstine. Surely Harry would have noticed the check was from a strange company and signed by someone other than Jarrett himself.