A Parole Board hearing was held on Tuesday to decide whether the convicted sex offender dubbed the Beast of Blenheim can be kept in prison for another four years.
Stewart Wilson was jailed for 21 years for sex offences against women, including rape and stupefying.
By 2 December he had served two-thirds of his sentence, and is eligible for release.
The Corrections Department applied to the Parole Board to keep Wilson in prison for another four years, saying he is untreated and still a risk.
However, Wilson countered that with a writ of habeas corpus, a rare judicial procedure that demands immediate release from prison.
Representing himself, he told the High Court at Christchurch that it was unfair for the Department of Corrections to try to keep him in prison any longer.
He referred to the cases of convicted rapists Brad Shipton and Bob Schollum, saying neither received treatment but had been released from prison.
However, Justice Chisholm ruled Wilson's argument invalid.
The Corrections Department then made submissions to the Parole Board to keep Wilson in jail until 2012.
Victims and a psychiatrist also gave evidence.
The board's decision is not expected until next week, although it could be reserved until the New Year.
