Robert Shaw claimed that he never received his fifty thousand dollar salary.
Robert Shaw had written an early adaptation of the novel in the mid 1960s, which had been rejected by Paramount Pictures.
In the conversation between the detective and his suspect, the suspect refers to a pistol as a revolver. It is actually a semi-automatic.
Jon Voight described the film's director Maximillan Schell, as a stiff individual with no sense of humour. Voight spoke more positively of Robert Shaw, saying he was exciting to work with, and also stimulating. They sometimes played games of table tennis during production.
"Friedrich" was consulted to shed some light on Kommissar Bärlach's motives. Friedrich was played by Friedrich Dürrenmatt, who wrote the book on which the movie was based.