Claude Chabrol thought that New York, home of Ed McBain's "87th Precinct", was too unwieldy, so big that it would obscure his intimate explorations of character and swallow the movie, so Chabrol instead relocated Ed McBain's "87th Precinct" to Montreal, Canada which spoke his native tongue of French but still had a North American setting. Despite being set in Canada rather than the USA where Evan Hunter's source novel was set, the movie still retained the "87th Precinct" for the picture.
First English language film of French director Claude Chabrol. Though filmed in Canada which hosts both French and English as native languages, French director Claude Chabrol chose to shoot the film in English rather than French as he felt the story would work better on film in the native language of its novel.
Donald Pleasence once said of this film, "...in Chabrol's film Blood Relatives (1978), shot in Canada, I was interrogated by Donald Sutherland about the assault on a thirteen-year-old-girl. A few days later, I caught a plane and I was playing a Chief of Police myself".