Erin Patterson one of few Australians sentenced to die in prison

On Friday, Victoria's Court of Appeal ruled Erin Patterson will spend the rest of her life behind bars with no chance of parole.

WARNING: The following story contains graphic details that may distress some readers.

A life sentence with no parole is a sentence rarely handed down in Australia, with only a handful of people across the country's prisons currently serving such a sentence.

In a country with no death penalty, it is the harshest punishment our criminal justice system can hand down to a convicted person.

Many of Victoria's most notorious killers, including Adrian Bayley and Jaymes Todd were sentenced to life in prison, but had non-parole periods affixed to their sentences, leaving the door open to eventual freedom.

But Justice Stephen McLeish said Patterson's offending was "extraordinarily cold and calculated and stands to be denounced in the strongest terms".

Former criminal barrister Christopher Corns described the sentencing as "an exceptionally rare event".

"[There is] a very strong presumption that even in a case of murder, where a head sentence of life is imposed, then a non-parole period must be set. This is exactly what the sentencing judge did in Patterson's case," he said.

"There have only been three [or] four cases where a court in Victoria has refused to set a non-parole period where the head sentence was life."

Dr Corns said he could not think of any other case where the Victorian Court of Appeal had re-sentenced someone and arrived at a non-parole period.

Erin Patterson's re-sentencing thus puts her in a rare grouping of convicted killers in Australia who will never be eligible for parole.

Michael Cardamone is currently serving a life sentence without parole for the murder of his neighbour Karen Chetcuti near Wangaratta in 2016.

The murder, which involved extensive torture, was described by Justice Lex Lasry as "quite simply horrifying, depraved and disgusting", with the veteran judge saying he was shocked by the crime.

A long-time methamphetamine user, Cardamone was on parole at the time of the murder for raping a 15-year-old girl.

Cardamone initially tried to pin the murder on a group of fictional Lebanese men who he said had threatened him to stay quiet, before later attempting to shift blame to a friend who had unwittingly helped him set fire to Ms Chetcuti's car.

He later attempted to have the friend murdered to prevent him from giving evidence at trial.

One of Victoria's most notorious serial killers, Peter Dupas is serving multiple life sentences over the murder and mutilation of several women in the late 1990s.

Dupas served multiple prison sentences from the 1970s to the 1990s for attacks on women.

Nicole Patterson, 28, was killed at her Melbourne home on April 19, 1999 and Margaret Maher's partially-clothed body was found on October 4, 1997.

In 2008, Dupas was found guilty of the murder of Mersina Halgavis, but that conviction was later overturned by the Court of Appeal and a retrial ordered. A second jury convicted him again.

"At a fundamental level, you present for us, the awful, threatening and unanswerable question: how did you become to be as you are?" Justice Elizabeth Hollingworth asked during his sentencing.

"You will now live out the rest of your days in prison."

Serial killer Paul Haigh is currently serving six life sentences for a series of murders in the 1970s, and a prison murder in 1991.

In 1979, Haigh murdered his friend Wayne Keith Smith, along with Mr Smith's ex-girlfriend Sheryle Ann Gardner and her 10-year-old son Danny Mitchell.

The same year, he stabbed his 19-year-old girlfriend Lisa Maude Brearley 157 times.

While in prison, Haigh confessed to the 1978 murders of Tattslotto agency worker Evelyn Adams and pizza shop worker Bruno Cingolani.

He was also convicted of hanging fellow Pentridge inmate Donald Hatherley in 1991, but argued it was an assisted suicide.

In 2009, Supreme Court Justice Betty King ordered Haigh never be released.

Haigh applied to the Victorian Supreme Court in 2012 to be given a minimum jail term, but was denied.

Former meatworker Katherine Mary Knight became infamous after becoming the first Australian woman to be sentenced to life in prison without parole.

In 2000, Knight skinned and beheaded her partner John Price at his home in the NSW town of Aberdeen.

She then cooked parts of Mr Price's body in the oven, and arranged them on plates she left as meals for his son and daughter.

Justice Barry O'Keefe said at the time that "a crime of the kind committed by the prisoner calls for the maximum penalty the law empowers the court to impose".

Knight's file is marked "never to be released".