The Court of Appeal has ruled that the Corrections Department followed proper procedures when deciding to keep the man dubbed the 'Beast of Blenheim' in prison beyond his scheduled release date.
Stewart Murray Wilson was due for release in December, having served two-thirds of a 21-year sentence imposed in 1996 for rape, indecent assault and other offences.
However, the Parole Board accepted he was at serious risk of re-offending and granted a Department of Corrections application to continue his imprisonment.
Wilson then applied for a writ of habeas corpus, which could have resulted in immediate release from prison, but the High Court dismissed his application.
The Court of Appeal ruled on Thursday that decision was correct and Wilson's continued imprisonment is lawful.