Karen Allen was never shown a complete script before she worked on this film. Director William Friedkin deliberately kept the actress in the dark about the events of the film since her character Nancy wasn't supposed to be aware of what was happening to Al Pacino's cop as he explored the gay underworld.
In 1972, director William Friedkin - huge after The French Connection (1971) - is shooting his spiritual/psych-horror The Exorcist (1973) in downtown New York. For a scene requiring mock brain-scans of the possessed lead character, Friedkin films a real-life radiologist and his assistant, Paul Bateson. Flash ahead to 1979. Friedkin is planning an adap of Gerald Walker's novel 'Cruising', inspired by a real-life serial killer carving up leather boys in the city's underground gay-bars and dumping their body parts in the Hudson River, wrapped in black plastic bags. When he learns that his Exorcist radiologist assistant Bateson is currently awaiting trial for the post-coital slaying of gay film critic Addison Verrill, Friedkin decides to pay him a visit to do a little research into the psyche of his cruising killer. Bateson is later imprisoned for life - for the Verrill murder - but not before dropping hints while in custody that he was also the body bag killer. The latter cases remain unsolved, but there's every chance that Friedkin had not only inadvertently consulted the actual killer at the heart of Cruising while planning the film, but had also cast him in a film he made years before it.
Rumor has it that William Friedkin's original cut ran 140 minutes. There is an increasing demand for a home video release of this version, if the deleted footage still exists and was not, as commonly believed, destroyed by United Artists. Apparently, Friedkin delivered this cut to the studio and this cut was condemned by the MPAA for ultra-provocative content. Mr. Friedkin has alternately said that all of the footage he was ultimately forced to cut (over a series of 40 different edits, at a cost of $50,000, before the MPAA finally granted the film an R rating) involved graphic sexuality and wasn't connected to the murder investigation plot, and that the footage did provide some "twists and turns in the story" that were not present in the film's final cut.
In 1977 and '78, New York homosexuals were terrorized by a series of "bag murders," in which six male victims were mutilated and dismembered , their remains wrapped in black plastic bags and dumped in the Hudson River. Some of the grisly fragments washed up on the New Jersey shore, others coming to ground near the World Trade Center. Police traced items of recovered clothing to a shop in Greenwich Village, catering to gays, and distinctive tattoos identified one of the victims as a known homosexual. Lacking identities and confirmed cause of death in several cases, the crimes were not officially classified as homicides, but were listed as CUPPI's - circumstances undetermined pending police investigation. A solution in the case derived from evidence collected in an "unrelated" case. On September 14, 1977, film critic Addison Verrill was beaten and stabbed to death in his New York apartment. Charged with the slaying, Paul Bateson, a 38-year-old X-ray technician, confessed to meeting Verrill in a Greenwich Village gay bar. After having sex at Verrill's flat, Bateson crushed his victim's skull with a metal skillet, afterward stabbing Verrill in the heart. Convicted of the homicide on March 5, 1979, Bateson drew a term of 20 years to life in prison. While in custody, awaiting trial, Paul Bateson bragged of killing other men "for fun," dismembering their bodies, and dropping the bagged remains in the Hudson River. Detectives satisfied themselves of Bateson's guilt, but he was never charged, and the "bag murders" - that later inspired the movie Cruising - remain technically unsolved.
The LA punk band The Germs recorded five or so songs expressly for the soundtrack to this movie, although in the actual event, only "Lion's Share" was actually used. During the recording sessions, director William Friedkin was so energized by the Germs' playing that he took to doing the "pogo" dance around the engineer's booth.
Along with being met with protest upon its release, the actual production of the film was plagued with demonstrations. Protesters would clog streets, make lots of noise to ruin live recorded sound, and even climb up on rooftops and shine light with reflectors down on to the set to mess up lighting and distract the crew.
Joe Spinell made this movie before Maniac (1980), playing a brutal, closeted police officer in the early scenes. His character mentions his wife leaving him and moving down to Florida with their young daughter to live with his wife's sister. In real life, Joe Spinell's wife, Jean Jennings, divorced him several weeks before he filmed his scenes, and moved to Florida exactly as Joe's character describes in the movie.
In an effort to make the scenes of gay "leather bars" as real as possible, actual gay bars for men were used in the film that existed in New York City at that time. These locations are in the lower west neighborhoods in the meat packing district of Manhattan, most of which remain open to this day. Movie extras in full black leather and chaps, including other provocative sexual attire, were actual gay patrons of the bar recruited for the scenes a few days before filming began. The extras were instructed to act as they would normally act in gay bars, but to tone down sexually-oriented activities because of the likelihood these acts would give the film an "X" rating.
During murder scene in a room at the St. James Hotel where a man is stabbed to death on a bed, director William Friedkin edited in several near-subliminal frames from a gay hardcore movie that can clearly be seen in slow motion on DVD.
The plot of the film, about murders in gay nightclubs, caused many to protest the release of the film. In fact, organized protests by gay groups were planned for the date of the release of the film. The public largely ignored the protests.
Angered over reports of the film's negative portrayal of gay life that leaked out during shooting, activists distributed hundreds of whistles to members of the city's gay community and encouraged them to spoil exterior filming on New York streets by blowing whistles loudly whenever they spotted film crews, a tactic that supposedly cost studio lots of money in lost time and post-dubbing.
William Friedkin initially wasn't interested in the project when producer 'Philip d'Antoni' first brought it to his attention. D'Antoni then tried Steven Spielberg who dropped out when - not surprisingly - none of the major studios were prepared to back it.
William Friedkin returned to the project when some well-publicized killings in the gay community emerged. He recalled the Cruising (1980) project that The French Connection (1971) producer 'Philip d'Antoni' first talked to him about a few years earlier.