Other mistake: In the party scene, there's a band playing on a stage. You can hear a big band playing, with lots of horn players, but the music that is heard has absolutely nothing to do with the players, who play guitar, accordion and double bass.
Continuity mistake: At the beginning of the film, in the scene when Ed is cutting Tolliver's hair, we see Ed holding scissors with his thumb and middle finger, yet, in the following shot he is holding them with thumb and index finger. There was no time nor need to change fingers; besides, a clipping sound is heard throughout the scene, which implies Ed never takes off scissors in order to change fingers. (00:10:05)
Continuity mistake: In the scene when Ed first meets Freddy at Da Vinci's, Freddy is having fruit cocktail, with his hand holding up the spoon close to his mouth, as he is taking the bite, shot from behind his back. When the angle changes to in front of him, we see his hand away from his face and there's no bite in his mouth.
Factual error: Ed Crane is executed by electrocution at the end of the film. However, in 1949, when the film is set, the gas chamber was used as the sole method of execution. According to the California Department of Corrections and Rehabilitation, California has never used the electric chair as a means of capital punishment.
Factual error: In one scene, after finishing playing the middle movement of the Sonata Pathetique, Bertie states that Beethoven was completely deaf when he wrote it and never heard the notes. This is untrue as the sonata was written in 1797/8 and Beethoven did not go totally deaf until 1823.