John Addison's car registration reads that his license plate number is "KYL-907." However, this license plate is actually seen on Edgar Ferrell's car. (BTW, viewers never saw any plate on John Addison's car, only his registration.)
Near the beginning, at the beach house, when Veronica Dale goes out the back door, when the door closes, the wall beside it shakes, revealing that it's on a film set, not part of an actual house.
The murderer hides the murder weapon in a location where the police should have found it.
At 4:23 Veronica Dale takes a curious sidestep to hit her mark visible as a black T on the floor.
When Veronica is picked up the first time, you can see the film crew reflected in the side of the car. The person holding the boom mike is easy to make out.
The prosecution claims a match between the murder bullet and another bullet fired from a gun owned by the defendant. The gun itself is missing, and where and how the second bullet was obtained is not explained.
While in the courtroom, Della fails to recognize Myrtle Northrup, who she had met as Veronica Dale's mother at Perry's office.