[6] It has since undergone a reevaluation, and has become a cult classic due to the presence of Keitel and Lydon, while being acknowledged as a precursor to Abel Ferrara's celebrated and similarly-themed film Bad Lieutenant (1992).

[6][7] Corrupt NYPD narcotics detectives Fred O'Connor and Bob Carvo have spent their illegal earnings on a Park Avenue apartment, viewing it as a sort of long-term investment.

Carvo's wife Lenore, a journalist critical of the police and a former fling of O'Connor's, begins to suspect her ex-partner's corruption, but cannot prove it.

Based on news reports, O'Connor determines that Mason's real name is Leo Smith, and tracks down his grandmother Margaret on Staten Island.

Margaret, a wealthy heiress, says that Leo came under her care after his parents' death, but felt guilty about the wealth he was now entitled to, and developed a self-loathing complex that led him to compulsively confess to heinous crimes he had no involvement in, seeking retribution over his self-inflicted guilt.

Holding him at gunpoint, Carvo demands he release Leo, but O'Connor responds by striking him and knocking his head on a toilet seat.

O'Connor's mental state further deteriorates as he descends into alcoholism, seeking comfort in the presence of Lenore, who still has feelings for him after her husband's death.

While O'Connor goes to Lenore's house, Leo dresses as a picture of his father and retrieves a hidden gym bag from a subway station locker.

[9] Thorn EMI Screen Entertainment released the film on home video in America later in 1984 as part of a package they acquired from New Line.

TEN) along with other titles they then had rights to, including The Texas Chain Saw Massacre and The Cars That Ate Paris; the film was retitled Copkiller for television broadcast.

Scores of bad-quality copies have been floating around the market, usually either sourced from the Thorn EMI videotape, or a 16mm print of the edited-for-television TEN version.

[10] On July 24, 2017, Code Red DVD released the film on Blu Ray in America, sourced from the original New Line Cinema elements, obtained directly from the Warner Bros.

Well-known British film critic Barry Norman refers to Lydon's voice as a “speak-your-weight machine", and sums up by calling the movie "stupid".

John Lydon's Post-punk group Public Image Ltd (PiL) was supposed to score the soundtrack for the film and worked on the material with his band mates Keith Levene and Martin Atkins (over the phone, by long distance).

[5] In early November 1982 PiL announced the imminent release of a new single, "Blue Water", and a six-track mini album, You Are Now Entering a Commercial Zone, on their new label, which was supposed to feature the unused/unreleased music made for Copkiller.