Convicted rapist Stewart Murray Wilson is being kept in jail, with the Parole Board saying he still poses a very high risk.
Wilson is in prison for the multiple rapes of women, assault, drugging, ill-treatment of children and bestiality.
He has been released on parole before, in September 2012, but was recalled to prison on April 10 2013 for breaching some of his conditions.
The board says Wilson has made little progress in developing a safety or release plan and has essentially refused to engage in the process.
However, the board says his position changed when he appeared before it earlier this month and he made an undertaking to work cooperatively.
It says, though, it couldn't release Wilson because there was no release proposal.
Wilson repeatedly appealed against his recall to prison but the appeals were rejected by the Court of Appeal and the Supreme Court.
He will appear before the Parole Board again in July. Wilson's 21-year sentence will cease on 1 December 2015.