The longest-serving inmates in Kiwi jails have been behind bars for a combined total of more than 367 years - and some may never be released.

Information provided to the Herald by the Department of Corrections revealed the 10 prisoners who had spent the most days in prison.

As of May 20 the inmates - all men - have been locked up for a total of 134,156 days.

That's 367.55 years or 19,165 weeks.

The men are in prison for a plethora of offending including murder, sex crimes, manslaughter and bank robbery.

One of the men has permanent name suppression so cannot be identified, but the rest have lengthy criminal histories and many will be well known to most New Zealanders.

1. Alfred Thomas Vincent

Days behind bars 18,132

Vincent is New Zealand's longest-serving prisoner.

The Christchurch man was one of the first people to be sentenced to preventive detention after he was convicted in 1968 of performing indecencies on five boys aged 12-14, including brothers, over about a year.

He has spent more than 50 years in prison.

Vincent first became eligible for parole 37 years ago, and has been refused each time.

The only time the child sex offender has spent outside prison was during day passes and weekend leaves in the early 80s - which were revoked when he was caught talking to young boys.

Denis Luke, convicted over the 1996 murder of Christopher Crean in New Plymouth Photo / Native Affairs, Maori TV

2. Denis Richard Luke

Days behind bars 15,798

Luke was jailed for life for the murder of Christopher Crean on October 6, 1996.

This crime was committed while he was on life parole for another murder committed 21 years previously.

Luke was a Black Power gang member.

Crean, a father of four and devout Christian, was set to give evidence as a Crown witness in a police case against Black Power members who had attacked a rival gang member outside Crean's home.

The 27-year-old refused to be silenced despite threats and two unsuccessful attempts on his life, prior to being gunned down at his New Plymouth home in 1996 while his children were home.

Luke, along with Brownie Mane, Robert Shane Maru and Symon George Manihera were convicted of Crean's murder and sent to prison in 1997.

The Parole Board approved Luke's release from prison earlier this year and he was freed in July.

At the time of Corrections compiling the figures for the Herald, Luke was still incarcerated.

3. Inmate name suppressed

Days behind bars 14,621

4. Andrew Peter McGlynn

Days behind bars 14,239

McGlynn was convicted of murder in 1986.

While on parole in 1994, soon after his release, he committed an armed robbery.

McGlynn was released again in 2003 but recalled soon after for aggravated robbery.

In 2005 he was granted parole but recalled for assaulting a woman.

He was recalled yet again after he breached his parole conditions in 2018.

5. Dean Hugh Te Kahu William Wickliffe

Dean Wickliffe, one of New Zealand's most high-profile criminals and prison escapees. This photo was taken last year before he was recalled to prison. Photo / Brett Phibbs

Days behind bars 12,492

Wickliffe is one of New Zealand's most notorious inmates.

He's got more than 50 convictions and after being paroled was recalled to prison earlier this year after being caught drink driving several times.

His raft of convictions include robbery, burglary, theft, drug offending and manslaughter.

Wickliffe's longest and most serious lag started in 1972 after he killed Paul Miet during the robbery of a jewellery store in Wellington.

He is also the only man to have escaped from the country's toughest prison twice.

In an exclusive interview with the Herald during his short parole stint last year, Wickliffe revealed his fractious and traumatic childhood led him down the dark path of crime and the destruction of himself and others.

The first crime Wickliffe ever committed was alongside a cousin, who was a couple of years older.

They broke into a warehouse where Wickliffe had been working and pinched £350 - the equivalent of an average yearly wage at the time - and fled to Auckland.

The pair enjoyed the spoils of their crime, the freedom it gave them to have money for once, to be able to buy food and all of the other things young lads want in life.

After three months the cash was all spent, but by then Wickliffe was "hooked on the lifestyle".

6. Roberto Conchie Harris

Days behind bars 12,414

Harris is best known for being Witness C - a jailhouse snitch who gave crucial evidence that sealed the fate of David Tamihere.

Tamihere spent two decades in prison for the murders of Swedish backpackers Sven Urban Höglin, 23, and his fiancée Heidi Birgitta Paakkonen, 21, which he has always denied committing.

But the Crown seconded three secret jailhouse informants to give "powerful" testimony at Tamihere's trial - testimony that sent him to prison for life.

After many years and a lengthy legal battle, the Herald was able to reveal Harris as Witness C.

Aside from his role in the Tamihere case, Harris was a serious offender in his own right.

He was jailed for the murders of Northland couple Carole Anne Pye and Trevor Martin Crossley in the early 80s.

Pye's three children, then aged 10, 9 and 7, found their mum and her partner's bodies with gunshot wounds to their heads when they returned home from school on February 22, 1983.

His trial for the double murder didn't go without incident either.

It was delayed after he was injured while attempting to escape from Mt Eden Prison in September 1983.

He was discovered outside the prison grounds after seemingly falling while climbing the perimeter wall and was treated for a broken hip and ankle.

His first conviction came in 1964 when he was just 15 years old.

When released on parole in 1995 for the Northland killings, he soon committed a serious assault and was recalled to prison.

Later in October 2008, he was found guilty of performing an indecent act on a young girl on the same day he was released.

Convicted murderer David Tamihere at the Auckland High Court hearing for the trial of Roberto Conchie Harris aka Witness C. Photo / Jason Oxenham

7. John Douglas Bennett

Days behind bars 11,772

Bennett has been convicted of sex attacks on 10 women across a 16-year period, beginning when he was just a teenager.

He also carries a conviction for the attempted murder of his last victim in 1986 after he abducted and raped her.

According to The Press Bennett severely beat the woman and forced her to dig her own grave.

She later fell from the boot of a car, unconscious, naked, bound, and gagged which likely saved her from being killed.

8. Phillip Laurence Tipene

Days behind bars 11,675

Not much has been published about Tipene's offending.

But he was convicted of indecently assaulting a 13-year-old girl in early 1986.

He was also convicted of indecent assault on a girl under 12 in 1981 and rape and indecent assault of a girl between 12 and 16.

9. Peter Joseph Holdem

Peter Joseph Holdem on the day of his arrest for the murder of Louisa Damodran in 1986. Photo / File

Days behind bars 11,534

Peter Joseph Holdem was jailed for life in 1987 for murdering 6-year-old Louisa Damodran near Christchurch.

When he killed Louisa, Holdem had just been released from prison for the abduction and attempted murder of a 10-year-old girl.

He has appeared before the Parole Board multiple times and been rejected repeatedly.

Little Louisa was walking home from school when Holdem kidnapped her, throttled her and dumped her body in a river.

A Parole Board report from 2016 said Holdem, then aged in his late 50s, has a "lifelong personality disorder with low intelligence".

In 2007, he was assessed by a psychologist, who found: "Mr Holdem probably has had more treatment for his sexual offending than almost any other offender of this type, with little apparent gain."

Holdem was eligible for parole in October 1996 and has now been in prison for more than 30 years.

When he first came up for parole the officer in charge of the case spoke about Holdem.

Former detective Mel Griebel, now retired, said he still had nightmares about the case.

"Whatever the psychiatrists and psychologists say, they can't guarantee he won't kill again," he said.

"He will come out and kill again. There is no doubt about that. I don't know what treatment he has had but he is not worth the risk."

10. Gary Lawrence McKinley

Days behind bars 11,479

In November 1986 Wendy Snowdon, 23, was jogging through a New Plymouth park when she chanced upon McKinley.

As she ran, McKinley was hiding in bushes near the track.

He knocked the woman unconscious with a rock and carried her to a remote location in the park where he raped her.

He strangled Snowdon and thinking she was dead, left her lying on the track.

A dog walker found Snowdon who was still alive. She was rushed to hospital but died of her injuries more than two weeks later.

McKinley was later charged with murder.

At the time he was 26 and unemployed.

He tried to claim that he had multiple personalities but after a psychiatric evaluation that was discounted.

In June 1987 McKinley was sentenced to life imprisonment for murder and six years jail for the rape charge.

Gary McKinley appearing in the Wellington District Court after he was charged with attacking a prison guard. Photo / NZPA