Raymond John Belsey, 29, is serving nearly six years’ imprisonment, a term which is due to end in August next year.
He came before the Parole Board last month maintaining his innocence over the sex attack.
"Mr Belsey told the board he believed he was wrongly imprisoned," panel convener Mary More said.
"The board had the assistance of a psychological report that said he was at very high risk of general offending and high risk of violent offending."
Belsey had an extensive criminal history involving violence, threats and was in jail for robbery in July 2020 when he was double-bunked with the victim.
When Belsey made sexualised comments about a young girl who featured in a television advertisement, the pair had a heated argument.
The defendant responded by smashing the remote, jumping down from the top bunk and slamming the television on the floor.
While the victim was face down on his bed, Belsey ‘‘effectively pinned him against the cell wall’’ and committed the violation.
The victim was later handcuffed to Corrections officers while undergoing an intrusive medical examination following the sex attack and received an apology from the prison manager for his treatment.
The episode prompted a change in protocol — now a Corrections nurse accompanies any inmate during such an assessment, while officers remain outside the room.
Belsey was found guilty at jury trial and was also convicted of wilful damage for smashing a wood panel in the Dunedin District Court’s ornate high courtroom.
Both the Court of Appeal and Supreme Court rejected his argument there had been a miscarriage of justice.
The Parole Board heard Belsey’s erratic behaviour had continued during his stay behind bars.
He was a high-security prisoner "following a number of incidents" and was subject to a management plan because of damage to Corrections property. There was now insufficient time left on Belsey’s sentence to undertake intensive rehabilitation and he had only completed a single session with a psychologist.
The inmate missed the follow-up appointment because he was "too busy in the wing and in the gym", the board heard.
"He is happy to wait in high security until his statutory release date," Ms More said.
Belsey had been accepted into transitional accommodation for men with complex needs but remained an undue risk of release.
He would next see the Parole Board in May.
