Key Points:

The trial of John Dewar was the final in a complex series of investigations and court cases that go back more than a decade.

Dewar was a Detective Inspector in charge of the Rotorua CIB when he met Louise Nicholas in 1993.

She had gone to police with allegations involving a police officer, who cannot be identified, and Dewar took her statement. He investigated and arrested the officer, charging him with offences against Mrs Nicholas.

During the course of the inquiry, Mrs Nicholas said she told Dewar that Clint Rickards, Bob Schollum and Brad Shipton had sexually assaulted her and used a baton on her at a Rutland St address in Rotorua.

Dewar denied she had told him that.

The claims were not allowed in the December 1993 trial of the unnamed officer, where Dewar gave inadmissible hearsay evidence and a mistrial was ordered.

After the aborted trial, Dewar spoke to Brad Shipton and telephoned Rickards, who was then based in Invercargill. Shipton and Rickards admitted consensual group sex with Mrs Nicholas.

The officer's second trial got under way in June 1994, where Mrs Nicholas was allowed to give evidence about Shipton, Schollum and Rickards. She said the sex was not consensual and involved a baton.

At the trial, Dewar gave inadmissible hearsay evidence about Rickards, Shipton and Schollum. He also spoke to Mrs Nicholas during an adjournment and a mistrial was called.

In the third trial of the unnamed officer, held in September 1994, Mrs Nicholas repeated her allegations of rape and use of a police baton. Shipton, Schollum and Rickards - giving evidence for the Crown - admitted consensual activity but denied using a baton. The officer was acquitted on all charges.

In a follow-up report to Internal Affairs, Dewar made no mention of the allegations against Shipton, Schollum and Rickards.

Early the following year, Detective Chief Inspector Rex Miller was assigned to review Dewar's investigation into the unnamed officer's case.

He visited Mrs Nicholas, who outlined the rape and baton allegations and gave a statement.

Mr Miller was directed by then-Regional Commander, Assistant Commissioner Bruce Scott, to investigate the allegations. He interviewed Shipton, Schollum and Rickards in May 1995.

During the Miller investigation, Dewar also conducted his own interview with Mrs Nicholas, in which she said the sexual activity with Shipton, Schollum and Rickards was consensual. Mrs Nicholas says she signed the document but had not written it, in order to help Dewar out because he was under pressure after the mistrials.

Mr Miller told the Dewar trial that the statement "totally destroyed her credibility" and any possibility of a criminal case against Shipton, Schollum and Rickards. He recommended the complaint against the trio not be upheld.

Fast-forward nine years, when Louise Nicholas was approached by a reporter investigating her allegations and Dewar's handling of the complaint.

Operation Austin was launched in early 2004 and led to four major trials, the first of which involved the kidnapping and rape of a woman in Mt Maunganui.

After the noise of the Nicholas allegations, the trial of Shipton and Schollum, lifeguards Peter McNamara and Warren Hales and a fifth man proceeded quietly due to a number of suppression orders. The men were convicted of kidnapping and raping a 20-year-old woman in Mt Maunganui in 1989.

A year later, with Shipton and Schollum serving prison sentences for the Mt Maunganui rape, they went on trial with Rickards over the Louise Nicholas allegations.

All three were acquitted but several months later were on trial again, in February this year, on charges of kidnapping and indecently assaulting another Rotorua woman with a whisky bottle in 1984, when she was 16. Again, the men were acquitted and suppression orders on Shipton and Schollum were lifted, revealing they were convicted rapists. The last major trial - that of Dewar - took everyone back to the beginning.