Warning: Graphic content and sexual violence themes.

Stewart Murray Wilson, the man infamously dubbed the Beast of Blenheim, has had his appeal thrown out after being found guilty of three more sexual offences, including the rape of a then 9-year-old girl.

The 72-year-old challenged his latest convictions and sentence for historical offending in the Court of Appeal in August after police reinvestigated the notorious sex offender in 2016.

Today, New Zealand's second highest court released its decision - dismissing Wilson's appeal.

During the hearing, Wilson claimed the Crown had abused the judicial process by charging him in spite of a stay on proceedings by the Attorney-General nearly 20 years earlier.

At a High Court trial last year Wilson was found guilty of raping a woman, a then 9-year-old girl, and of attempting to rape a third woman during the 1970s and early 1980s in Wellington, Hamilton and Auckland.

He was found not guilty of raping a fourth woman - the mother of the young girl.

One of the women, who gave pre-recorded evidence before the trial because she was ill, died shortly after the completion of the trial.

In providing their reasons, Court of Appeal president Justice Stephen Kós said: "Serious crimes should be prosecuted, despite delay by the complainant in making a complaint, unless prejudice compels a stay.

"In a case involving delay, the fundamental consideration remains whether a fair trial is possible. If a judge is satisfied that despite all proper directions being given to mitigate risk, a fair trial is not possible, then a stay should be granted.

"We are satisfied that the judge correctly identified the relevant principles, and applied them here appropriately."

Stewart Murray Wilson was dubbed "the Beast of Blenheim" after being convicted of multiple rapes in 1996. Photo / Supplied

Justice Kós said the 2018 trial judge, Justice Graham Lang, had noted the delay by the police in investigating two complainants claims which were made in 1996 and 1976.

"The judge took that delay into account, but concluded it was outweighed by the seriousness of the charges, the relative strength of the Crown case, and the ability of Mr Wilson to present a defence," he said.

"He was able to receive a fair trial. The jury acquitting on all charges in relation to complainant H tends to confirm that assessment."

The Court of Appeal also dismissed Wilson's appeal of his sentence.

Because he was sentenced to a concurrent term of two years and four months' imprisonment by Justice Lang last November, Wilson also had to leave his two-bedroom cottage on the Whanganui Prison grounds.

He had lived there since being released in 2012 - with an extended supervision order and the most stringent conditions ever imposed on a New Zealander - after he was sentenced in 1996 to 21 years' imprisonment for drugging, assaulting and raping several women, as well as charges of stupefying and bestiality.

However, just two days after the Court of Appeal hearing the Parole Board allowed Wilson to leave prison again and reside at a redacted Whanganui address.

Wilson returned to his cottage on the Whanganui Prison grounds on August 20.

At the time of his 1996 trial, Wilson had also faced a further 23 charges alleging sexual crimes against several other women.

But this second indictment was not used because the then law limited the number of charges which could be contained in a single indictment.

In 2000, the Attorney-General entered a stay of proceedings on the second indictment.

Wilson's lawyer Andrew McKenzie had argued in the Court of Appeal that the Crown had "called it quits in 2000".

McKenzie also applied for a stay on the new proceedings against Wilson before last year's trial, but was unsuccessful.

If Wilson had been charged in 1996 or 2000 with the additional historical offending, McKenzie said, then he would have already completed his sentence.

He said Justice Lang had not addressed the "inherent unfairness of facing charges for offending that he had already served any sentence for and which were somehow outside any prosecutorial decision in 2000 to let sleeping dogs lie".

Justice Lang had commented on the 2000 stay and said: "The reasons for the Attorney-General's decision [are] not entirely clear."

Stewart Murray Wilson looks on as his lawyer Andrew McKenzie addresses the court during his trial last October. Photo / Michael Craig

The reasons for the delay in trial, Justice Lang said, could be attributed, in part, to the police failing to investigate the allegations at the time.

"Although [one of the women] went to the police immediately after the alleged offending against her in 1976, the police took no steps at that time," he said.

"They did not begin to investigate the allegations until [she] contacted them again following the publicity surrounding Wilson's trial in 1996."

At Wilson's trial last year the jury was also prevented from knowing the criminal history of the man standing before them.

Justice Lang had dismissed the Crown's application to lead propensity evidence and also suppressed his infamous nickname.

"It is well-known he offended against woman, girls, animals - that's why it's the beast," McKenzie said of the nickname at a pre-trial hearing.

At the Court of Appeal hearing, McKenzie added: "I would've been surprised if there hadn't been someone on that jury who knew of his name and perhaps even his previous offences."

Justice Lang had said media coverage of Wilson during the past decade may have tainted the jury pool, "if only by the nickname the media have used".

In a handwritten letter to Justice Lang before last November's sentencing, Wilson said he was "sorry for my past action and any harm caused".

Stewart Murray Wilson, pictured during his sentencing in the Auckland High Court last year. Photo / NZ Herald

But, the Beast continued to deny knowledge of the offending.

"I do not have any recall of the people at the trial," he wrote. "I put this down to the shock treatments I received."

The majority of Wilson's historical offending - for which he was sentenced more than 20 years ago - occurred before New Zealand's courts could impose a minimum period of imprisonment.

At Wilson's sentencing in March 1996, the late Justice Richard Heron said the 21-year prison term was "a very long one in this country's history" but "justice requires nothing less".

An appeal of the 1996 matters by Wilson has already been dismissed by the Court of Appeal.