Key Points:

The inquiry into the police pack rapists uncovered up to a dozen other alleged women victims.

The officer who headed the Operation Austin investigation, Detective Superintendent Nick Perry, said the women told of sexual misconduct by the "core group" of officers around convicted rapists Brad Shipton and Bob Schollum.

The allegations were sent to a Crown Solicitor for a decision on whether charges could be laid, but were not put to a court for various reasons.

"Some people were reluctant to become involved, and some other people were willing to give evidence, but we had to ask if we had enough evidence to pursue it, " Mr Perry said.

Operation Austin began in 2004 after Louise Nicholas went public with allegations of pack rape in the 1980s by suspended assistant commissioner Clint Rickards and now-jailed former officers Shipton and Schollum.

On Wednesday, a jury found former detective inspector John Dewar guilty on four charges of mishandling and covering up her allegations.

At a trial last year, Rickards, Shipton and Schollum were acquitted of raping her.

Operation Austin found another Rotorua woman who accused the trio of raping her but they were also acquitted in that case.

Shipton and Schollum were convicted of pack-raping a young woman in Mt Maunganui.

Mr Perry said Operation Austin grew beyond Mrs Nicholas' allegations to 70 "phases" of investigation. Each was a separate allegation.

Some turned out to be unfounded rumours; others involved "tacit acknowledgment that something had happened" but the women had not wanted to take matters further.

Mr Rickards remains suspended on full pay, understood to be $150,000 to $159,000 a year, while he works through "employment issues" with the police.

Mr Perry said the decision by police chiefs - including former commissioner Rob Robinson - to keep promoting Mr Rickards when they knew about Mrs Nicholas' allegations was "naive" and "dangerous".

An inquiry into the case by Detective Chief Inspector Rex Miller in 1995 should have rung alarm bells, even though it was obstructed by Dewar's manipulation of Mrs Nicholas.

Herald: Do you think Mr Robinson made strange decisions?

Mr Perry: "You'd have to ask [him]. All I can say is that anybody reading [the Miller inquiry] who is an experienced police officer would have to have had some reservations about how it was concluded, or the conclusions that were reached, and certainly not be prepared to take them on face value."

"My understanding was it was put to [Mr Rickards] whether those allegations were true or not and his word was taken, which was probably a bit naive, given the fact I suppose as one rises higher in the police you come under more and more scrutiny.

"Given the flawed nature of the inquiry ... it was dangerous, I think, to take that at face value and that everyone had been cleared and there was no substance to it."

The proof of the pudding was the findings of the Dewar case, Mr Perry said, "because 75 per cent of the evidence we produced was already there in that file".

Mr Robinson retired before the cases came to court and has refused to comment on his involvement with Mr Rickards' rise from detective inspector to assistant commissioner.

Mr Perry said his team looked at laying conspiracy charges against Dewar, Shipton, Schollum and Mr Rickards but it was not thought there was enough evidence for a prosecution to succeed.

Mr Perry expressed his continued belief in Mrs Nicholas' rape claims, and described her as a "very tenacious character".

Responding to Mr Rickards' statement that Operation Austin was "a shambles", Mr Perry praised his team and the Crown prosecutors.

"We're always going to have accusations made against us ... I assume if he had been convicted it would have been an even bigger shambles."