From: Ian Pryor, Peter Jackson: From Prince of Splatter to Lord of the Rings: An Unauthorized Biography, St. Martin's Press: New York, NY (2004), pages 214-215:

When, shortly before the release of Heavenly Creatures, journalist Lin Ferguson revealed that the real-life Juliet Hulme was not an author named Anne Perry, Jackson and Walsh found themselves defending the accuracy of their account against one of the actual participants -- a woman who felt that Heavenly Creatures' very existence was morally questionable...

The media unveiling of Juliet Hulme made Jackson acutely aware that media ttention can be a double-edged sword. He has spoken of feeling guilt for the part Heavenly Creatures played in Hulme's rediscovery, and also expressed his anger at the journalist who found her (Ferguson, on the other hand, insists she refused to cash in on her scoop by selling the story overseas). The act of revealing the identity of someone who murdered, and paid for their crime, is arguably more questionable than Jackson's own actions: making a movie which quotes often from the personal diaries of a murderer. But balancing such ethical questions requires knowing exactly why Ferguson, Jackson and Walsh decided to tell the stories they did -- and untangling any desire thye may have had for success or fame from a possible desire for good.

My own belief is that Jackson took much of his own guilt at having turned the Parker-Hulme murder into a successful movie and laid it at the door of the media. This theory would help explain why Jackson allowed himself to throw a photo of Parker and Hulme onto the screen in the midst of The Frighteners, as if it was a kind of in-joke, just months after having been criticised in real life by Hulme/Perry for exploiting her story. The scene in The Frighteners (with Trini Alvarado's character watching a video about a serial killer) appears to be attacking media sensationalism of tragedies. But including an image of Parker and Hulme, however briefly, comes across as somewhat hypocritical, especially in a film which itself plays murder largely for sensation and entertainment.