Goofs

(at around 13 mins) When Joe took the "Nocturne" song sheet (aka music manuscript paper) from Vincent's home, 16 of the 20 music staffs contained musical notes and the last four staffs are empty. However, when Joe brings the song sheet home to his mother, this time 19 of the 20 music staffs contain music notes, and only the last staff is empty.

(at around 2 mins) When the "Nocturne" sheet music is seen on the piano in the film's opening shot, it is comprised of two pages with 20 music staffs containing musical notes on each staff. However, when it cuts to another shot of the sheet music, only 16 of the 20 staffs contain musical notes.

When Joe enters the club salon after the fight with Torp, his left shirt collar is disheveled and the right collar remained neatly in place. But when Joe approaches Fingers at the piano and it cuts to a close-up of Joe, now both collars are disheveled.

(at around 18 mins) When the waitress is carrying a cup of coffee with her right hand, the camera is filming the mirror; therefore, it is really her left hand since it is a reverse image of the real action. The next cut of her arriving at Lt. Warne's table is shot straight on without using the mirror, and she is carrying it in her right hand, but it should be the left hand.

When Vincent is playing the piano, his white shirt cuffs are showing. When the camera goes to a close-up of the piano playing, the arms/hands show no cuffs, but reappear when Vincent is on screen again.

The exterior shot of the Pantages Theatre shows RKO's From This Day Forward (1946) on the marquee, which indeed was being shown there in June 1946 when Nocturne was filmed. However, in the close-up at the box-office, RKO's The Woman on the Beach (1947) is on the time schedule; the latter film was in production at the same time as Nocturne, but, due to unforeseen production delays, did not open at the Pantages until over a year later, in July 1947.

Fingers is playing a spinet piano, but the sound is that of a grand piano.

When Joe's mother and her friend are discussing the switching of fingerprints in the Vincent murder case, the friend mentions that she saw Ginger Rogers do the same thing in "Blue Midnight". However, this is wrong. Ginger Rogers never did a film called "Blue Midnight"; the name of the film was actually called Star of Midnight (1935).

The black and white police car that Joe steals at the photographer's studio doesn't have a city name on the door.