Merle Oberon fell in love with the film's cinematographer, Lucien Ballard, and they married the following year. Because of facial scars Oberon sustained in a car accident, Ballard developed a unique light for her that washed out any signs of her blemishes. The device is known to this day as the Obie (not to be confused with the Off-Broadway award).
There is a real Black Museum (now called the Crime Museum) at Scotland Yard. It officially came into existence in 1875 and has a police inspector and a police constable assigned to official duty there. It is not open to the public, but can be visited by police officers from any of the country's police forces by appointment.
Laird Cregar's screen presence and performance created such a sensation that Twentieth Century-Fox planned to cash in on its find by putting him in similar roles in other productions. The first of these was Hangover Square (1945), which reunited director John Brahm, screenwriter Barré Lyndon, and co-star George Sanders. The plans were cut short after Cregar had a fatal heart attack at the end of the year. "Hangover Square" would be released after his death.
One of the first movies to have a point of view shot showing the killer's perspective.