Who was the killer in Basic Instinct?

Did Catherine Tramell commit the murders in Basic Instinct or was it someone else?

Basic Instinct is a 1992 neo-noir erotic thriller film directed by Paul Verhoeven and written by Joe Eszterhas. The film follows San Francisco police detective Nick Curran (Michael Douglas), who is investigating the brutal murder of a wealthy rock star. During the investigation, Curran becomes involved in a torrid and intense relationship with the prime suspect, Catherine Tramell (Sharon Stone), an enigmatic writer.

Eszterhas developed the script in the 1980s. It became a subject of a bidding war until Carolco Pictures acquired the rights to the film. From there, Verhoeven signed on to direct and Douglas and Stone joined the project, after many actresses were considered for the role of Tramell. Before its release, Basic Instinct generated controversy due to its overt sexuality and violence, including a rape scene. Gay rights activists criticized the film's depiction of homosexual relationships and the portrayal of a bisexual woman as a murderous psychopath. In one scene, Stone's vulva was filmed as she crossed her legs, which she claims was done without her knowledge.

Basic Instinct premiered in Los Angeles on March 18, 1992, and was released in the United States by TriStar Pictures on March 20, 1992. It received mixed reviews from critics, who praised the performances of its cast, original score, and editing, but criticized its writing and character development. Despite these reviews and public protest, Basic Instinct was a box office success, grossing $352 million worldwide, making it the fourth highest-grossing film of 1992 behind Disney's Aladdin, The Bodyguard, and Home Alone 2: Lost in New York. Several versions of the film have been released on videocassette, DVD, and Blu-ray including a director's cut with extended footage previously unseen in North American cinemas.

The film was later recognized for its groundbreaking depictions of sexuality in mainstream Hollywood cinema, and was described by one scholar as "a neo-film noir masterpiece that plays with, and transgresses, the narrative rules of film noir." A 2006 sequel (14 years later), Basic Instinct 2, also starred Stone and was made without Verhoeven's involvement, but received negative reviews and was relatively unsuccessful.

But one question that has remained on audience's lips is who committed all the murders in Basic Instinct?