WARNING: This story includes graphic details and may be upsetting.

A prisoner who violently attacked a fellow inmate, cutting his eyelids and slicing his neck 21 times has been sentenced to preventive detention with a minimum non-parole period of five years.

Anthony John Wheble, 27, was sentenced in the High Court at Auckland today for the 2020 attack with a homemade shank at Auckland Prison, Paremoremo.

When his sentence was handed down, Wheble refused to leave the courtroom and demanded to speak to the judge.

He fought security guards, headbutting one before yelling abuse at the judge.

"F*** you, Judge, you piece of s**t," he said.

Wheble disrupted the first attempt to sentence him in August when he leaped out of the dock towards counsel.

There were gasps from the public gallery as two security officers followed him, pinned him to the ground after a short scuffle and pulled him out of the courtroom.

Wheble had been serving a seven-year sentence for the attempted murder of a different inmate in 2018, a second strike offence, when he savagely attacked the other inmate in 2020.

• Court interrupted: Criminal who sliced inmate's throat leaps out of High Court dock
• Auckand prisoner now convicted twice of slashing fellow inmates' throats

Justice Graham Lang said today Wheble needed to be regarded as having deep-seated issues that needed to be addressed.

Crown prosecutor Matthew Nathan said Wheble posed a risk to the community for further violent offending, and he sought a sentence of preventive detention.

"The attack was prolonged, unprovoked and involved kicking and weapons.

"The aggravating features are quite startling, almost all aggravating features that were present in Wheble's previous offending are also present but to a higher degree in this offending."

Anthony Wheble moments before he jumped out of the dock and interrupted his sentencing hearing in August. Photo / Michael Craig

He said the level of violence was severe, and that Wheble posed a very high risk of reoffending.

"It is not just his violent criminal history. There are also matters that deal with the psychological issues that he currently has and appears to have had for his entire life.

"There is a lack of empathy for others, lack of insight into prior offending and he has the willingness to minimise his prior offending."

He said a starting point of 12 years was appropriate.

Wheble's lawyer David Hoskin sought a starting point of 10-12 years.

He emphasised that his client had pleaded guilty and that the court should bear that in mind.

"He is currently on waiting lists for rehabilitation to address his violent tendencies and drug needs," Hoskin told the court.

"He has realised he needs to reconsider his willingness to engage."

Hoskin told the court Wheble had strong family support but that his family had concerns about him being moved from Christchurch Prison to Otago and now to Auckland Prison.

"When he was in Christchurch his family were able to see him a bit but now they can't," he said.

Hoskin sought an extended supervision order on Wheble's release from prison.

Justice Lang said the attempted murder was more serious than his last attempt because of the vulnerability of the victim.

He gave Wheble a starting point of 12 years imprisonment but gave him discounts for his guilty plea and upbringing.

Justice Lang decided a term of preventive detention was the only way to keep the community safe.

"A sentence of preventive detention may help you to access help more quickly," Lang said.

The attempted murder

The January 2020 attack, involving an altered toothbrush with a razor blade attached, came just months after Wheble was sentenced to serve seven years without parole for slitting another inmate's throat at the Otago Corrections Facility.

According to an agreed summary of facts, the latest attack occurred in the exercise yard at Auckland Prison.

In the one-minute assault, caught on CCTV, Wheble cut the victim's eyelids and sliced the right side of his neck 21 times.

There had been no known incidents between Wheble and victim Brent Charlton, who was in two leg casts and was sitting against a wall.

The CCTV footage showed Wheble walking up to Charlton, a sex offender, and kicking him in the head.

Then with his left hand, Wheble lifted Charlton's head from the floor to his waist height and, with his right hand, took the shank from his pocket and repeatedly stabbed Charlton's face several times.

Wheble then let go of Charlton's head, took a step back and kicked him five times to the head.

With Charlton then unconscious, Wheble held up his head and continued to cut his eyelids, making 14 other cuts to his face and 21 cuts to his neck.

Wheble was first jailed in 2014 for committing a mini crime spree when he was 18.

- Ellen Thompson, Open Justice