The 1990s section of the film, focusing on a musician called Margot moving into the infamous house on Cielo Drive to write a new album, is very loosely inspired by the period when Trent Reznor of the Nine Inch Nails recorded several albums and lived at 10050 Cielo Drive in the early nineties.
This film does not adhere to the "Helter Skelter" motive for the murders put forth by prosecutor Vincent Bugliosi during the highly publicized trials of members of "The Manson Family". Drug dealing is the common theme running through the 1960s section of the film.
Linda Kasabian, who was present on the night of the real life murders at Cielo Drive, was originally included as a significant character in the script. An actress was cast to play the role of Kasabian but she left the production on her first day of filming after the caterer revealed there would be no chicken and chips served for lunch that day. Despite the caterer and producers agreeing to add chicken and chips to the menu the actress still opted to leave the set before filming any scenes as Kasabian. Unable to re-cast at such a late stage the producers decided to eliminate the character from the film and instead focus on the other "Manson Girls".
Ciaron Davies was cast as Charles Manson after submitting an audition tape in which he improvised for 10 minutes in character. The majority of his lines in the final film were improvised.
During the scene involving Margot injecting heroin, a dolly zoom shot is utilized. The shot is an in-camera effect that appears to undermine normal visual perception. The effect is achieved by zooming a zoom lens to adjust the angle of view (often referred to as field of view, or FOV) while the camera dollies (moves) toward or away from the subject in such a way as to keep the subject the same size in the frame throughout. The effect was first conceived by Irmin Roberts, a Paramount second-unit cameraman, in Alfred Hitchcock's film 'Vertigo' but audiences may be most familiar with it's use in 'Jaws'. The dolly zoom is commonly used by filmmakers to represent the sensation of vertigo, a "falling-away-from-oneself feeling" or a feeling of unreality, or to suggest that a character is undergoing a realization that causes them to reassess everything they had previously believed.