Almost all locations used for filming were the genuine locations where the events occurred. The tea shop where Honora Parker ate her last meal was knocked down a few days after the shoot ended. According to director Peter Jackson, when they got to the location of the murder on the dirt path, it was eerily quiet; the birds stopped singing, and it didn't seem right. So they moved along a couple of hundred yards.
Juliet Hulme was revealed to be mystery writer Anne Perry who came forward and revealed her real identity in 1994 during the making of the film, but all attempts to find Pauline Parker failed. In 1997, Pauline Parker was finally traced to a rundown cottage on a farm near Strood, Kent, England, where she currently runs a children's riding school. Since assuming the name of Hilary Nathan, she has become a devout Catholic and devoted her life to handicapped children.
All of the journal voice-overs are direct from real diary entries made by Pauline Parker. The characters in the stories (if not the stories themselves) and make-believe world are also authentic.
Melanie Lynskey was cast as Pauline Parker two weeks before filming began. Co-writer Fran Walsh discovered her at the last minute while scouring local high schools for Parker lookalikes.
Co-writer Fran Walsh suggested the idea of making the Parker-Hulme murder into a film to director Peter Jackson. Walsh said she had a fascination with the murder since childhood.
Since the Parker-Hulme murder had been an infamous crime that was strongly sensationalized in New Zealand history Jackson decided rather than do a film that would be a historical look back at the crime to instead create a drama about Parker and Hulme's intense friendship. In addition to reading Pauline Parker's diary Jackson and company undertook a nation wide search for anyone who had known the girls and interviewed them to get a closer look at their life.
One of the photographs that Juliet Hulme puts on display in the woodland shrine is that of tenor Jussi Bjoerling, who was (in real life) greatly admired by the girls' tenor idol, Mario Lanza.