A dangerous sex offender who tried to drag a Dunedin woman off the street into a van has failed to have an indefinite prison term lifted.

Joseph Warren Lepper (41) was sentenced to preventive detention after he and Zane Alexander McVeigh drove from Christchurch to Dunedin on October 19, 2013 and attempted to abduct a 22-year-old student.

Lepper drove slowly past the pedestrian on Vogel St, stared at the her and told McVeigh, ‘‘I’m going to do that bitch”, the court heard at sentencing.

He angle-parked the van in front of the victim and the pair set upon her.

The woman was able to fight off the men until nearby residents came to her aid but she was left bruised and missing handfuls of hair.

Lepper was slapped with an open-ended prison term because the incident came just seven months after he had been released from prison following a chillingly similar episode.

In 2002, the man forced a woman off the street and into a park where he raped her.

While in prison serving a 10-year stint, Lepper was also involved in various incidents, including two threatening to kill female staff members.

The High Court concluded the two attacks were of such a nature that a “pattern of serious sexual offending was established”.

Lepper challenged that ruling at the Court of Appeal.

He claimed the sentence of preventive detention was manifestly excessive because he did not understand what he was doing at the time of the offending so was effectively being punished for being unwell.

The court dismissed that argument, found any insight into his offending was “relatively recently developed” and noted Lepper had refused treatment while on parole.

His appeal was declined and, despite being more than two years outside the statutory time frame, the defendant attempted to take his case to the Supreme Court.

Lepper blamed the delay on his difficulty obtaining legal representation and his mental-health issues.

The Supreme Court ruled there was no basis on which he could challenge the previous decision and refused to grant leave for his appeal.

“No question of general or public importance arises,” the court said.

A psychiatrist who assessed Lepper concluded auditory hallucinations he experienced had not made him incapable of knowing what he was doing.

Further, Lepper had “provided clear information that he ... knew the moral nature of what he was doing at that time”.

Prisoners serving preventive detention may be released on parole but remain managed by Corrections for the rest of their life and can be recalled to prison at any time.