Lang placed an advertisement in a newspaper in 1930 stating that his next film would be Mörder unter uns (Murderer Among Us) and that it was about a child murderer. He immediately began receiving threatening letters in the mail and was also denied a studio space to shoot the film at the Staaken Studios. When Lang confronted the head of Staaken Studio to find out why he was being denied access, the studio head informed Lang that he was a member of the Nazi party and that the party suspected that the film was meant to depict the Nazis.[19] This assumption was based entirely on the film's original title and the Nazi party relented when told the plot.[20]
M was eventually shot in six weeks at a Staaken Zeppelinhalle studio, just outside Berlin. Lang made the film for Nero-Film, rather than with UFA or his own production company. It was produced by Nero studio head Seymour Nebenzal who later produced Lang's The Testament of Dr. Mabuse. Other titles were given to the film before "M" was chosen; Eine Stadt sucht einen Mörder (A City Searches for a Murderer) and Dein Mörder sieht Dich an (Your Murderer Looks at You).[21] While researching for the film, Lang spent eight days inside a mental institution in Germany and met several child murderers, including Peter Kürten. He used several real criminals as extras in the film and eventually 25 cast members were arrested during the film's shooting.[22] Peter Lorre was cast in the lead role of Hans Beckert, acting for the film during the day and appearing on stage in Valentine Katayev's Squaring the Circle at night.[23]
Lang did not show any acts of violence or deaths of children on screen and later said that by only suggesting violence, he forced "each individual member of the audience to create the gruesome details of the murder according to their personal imagination".[24]
Peter Lorre as Hans Beckert, gazing into a shop window. Fritz Lang uses glass and reflections throughout the film for expressive purposes.M has been said, by various critics and reviewers, to be based on serial killer Peter Kürten—the "Vampire of Düsseldorf"—whose crimes took place in the 1920s.[25][26] Lang denied that he drew from this case, in an interview in 1963 with film historian Gero Gandert; "At the time I decided to use the subject matter of M, there were many serial killers terrorizing Germany—Haarmann, Grossmann, Kürten, Denke, [...]".[27][28] Inspector Karl Lohmann is based on then famous Ernst Gennat, director of the Berlin criminal police.[29]
Lang's depiction of the Berlin underworld in the film was inspired by the real Ringvereine, which played a role in the German underworld analogous to the Mafia in the Italian underworld.[30] The film's portrayal of the Ringvereine as organized like companies with a board of directors that were dominated by a charismatic master criminal was based on reality.[30] Likewise, the practice of the Ringvereine shown in the film of providing financial support for the families of imprisoned members was also based on reality.[30] The break-in of an office building depicted in the film was inspired by the real life 1929 break-in of the Disconto Bank in Berlin by the Saas brothers gang, though unlike in the film the objective was larceny, not to capture a serial killer.[30] The Ringvereine, which were officially wrestling associations that existed for the physical betterment of German men, always sought to promote a very 'respectable', almost middle-class image of themselves.[31] Like the Mafia, the Ringvereine paradoxically portrayed themselves as the guardians of society's values, who upheld a certain social order. The image the Ringvereine sought to project was as "professionals" whose crimes did not harm ordinary people.[32] Though the Ringvereine were known to be gangsters, their hierarchal structure and strict discipline led to a certain popular admiration for them as a force for social order unlike the psychopathic serial killers who murdered random strangers for reasons that often seemed unfathomable, sparking widespread fear and dread.[32] In an article originally published in Die Filmwoche, Lang wrote that the crime scene in Germany was "such compelling cinematic material that I lived in constant fear that someone else would exploit this idea before me".[33]
The Weimar era was marked by intense debates about the morality and efficiency of capital punishment, with the left arguing that the death penalty was barbaric, while the right argued that the death penalty was needed to maintain law and order.[32] Adding to the debate was the popular interest in the new science of psychiatry, with many psychiatrists arguing that crime was caused by damaged minds and emotions, which could be cured.[32] In the background was a popular obsessive fear of crime and social breakdown, which was fed by sensationalist newspaper coverage of crime, which certainly gave the impression that crime was out of control in Weimar Germany.[32] In addition, for many conservative Germans, the Weimar republic was itself born of crime, namely the November Revolution of 1918 which began with the High Seas Fleet mutiny of October 1918. According to this viewpoint its origins in mutiny and revolution made the Weimar Republic into an illegitimate state that could not maintain social order because the Republic itself was born of disorder.[32] Lang followed these debates closely and incorporated them into several of his Weimar films such as M. The debate at Beckert's "trial" about whether he deserved to be killed or not paralleled the contemporary debates about capital punishment in Germany.[34] The fact that Der Schränker, a career criminal, serves as both the prosecutor and judge at the kangaroo court, egging on the mob of criminals to kill Beckert, seems to suggest that Lang's sympathy was with the abolitionists.[34] The arguments that Der Schränker makes at the kangaroo court, namely that certain people are so evil that they deserved to be killed for the good of society was precisely the same argument made by supporters of the death penalty.
The incorporation of social issues in the film can be seen through the lens of Jeffrey Jerome Cohen’s Monster Culture (Seven Theses). The first of these theses states that “The monster is born only at this metaphoric crossroads, as an embodiment of a certain cultural moment—of a time, a feeling, and a place.”[35] Beckert, as the monster in this film, embodies the cultural moment; he reflects Weimar society and its interest in morality and criminality. In other words, the classification of Beckert as a monster itself reveals the film’s incorporation of social issues.
Leitmotif
M was Lang's first sound film and he experimented with the new technology.[36] It has a dense and complex soundtrack, as opposed to the more theatrical "talkies" being released at the time. The soundtrack includes a narrator, sounds occurring off-camera, sounds motivating action and suspenseful moments of silence before sudden noise. Lang was also able to make fewer cuts in the film's editing, since sound effects could now be used to inform the narrative.[37] The film was one of the first to use a leitmotif, a technique borrowed from opera, associating a tune with Lorre's character, who whistles the tune "In the Hall of the Mountain King" from Edvard Grieg's Peer Gynt Suite No. 1. Later in the film, the mere sound of the song lets the audience know that he is nearby, off-screen. This association of a musical theme with a particular character or situation is now a film staple.[38] Peter Lorre could not whistle and Lang himself is heard in the film.[39]
