The Parole Board has explained its latest reasons for keeping a rapist dubbed the 'Beast of Blenheim' behind bars.
In 1996, Stewart Murray Wilson was sentenced to prison for 21 years for rape, bestiality, stupefying, ill-treatment of children and indecent assault over quarter of a century.
He was due to have been freed two years ago, but is being kept in prison under a special clause of the Parole Act because of the risk he poses.
radio New Zealand's justice reporter says Wilson is now in his mid-60s and continues to shun prison psychologists and parole assessors.
The board says it is looking for change in the risk he poses and whether that is diminishing with age.
But it has concluded that nothing has changed his case and release is neither applicable nor appropriate.
By law, Wilson must be freed in September 2012.