Police have admitted they used an incorrect DNA sample to rule out a paedophile priest in the brutal killing of Melbourne cold case murder victim Maria James.

The ABC understands a bloodied pillow case, used to establish a DNA profile for the suspected killer of the Thornbury single mother, came from an unrelated crime scene.

Local priest Father Anthony Bongiorno, as well as multiple other suspects in Maria James' 1980 murder, were cleared as a result of DNA testing against that incorrect sample.

Her two sons, Mark and Adam James, have now formally applied to the Victorian coroner to set aside the original finding and reopen the 37-year-old case.

Warning: This article contains content from the Trace podcast. If you would prefer to listen, head to the Trace site, and subscribe in iTunes or your favourite podcasting app via the RSS feed.

Police say bungle was human error

Maria James was stabbed 68 times in her home out the back of her Thornbury bookshop in what police described as a "bizarre" and "frenzied" killing.

Maria James murder: Stabbed 68 times in her Melbourne home

Stabbed 68 times in her Melbourne home Hands bound in what police described as a 'frenzied attack'

Hands bound in what police described as a 'frenzied attack' Youngest son abused by two local priests

Youngest son abused by two local priests One priest seen covered in blood on day of murder

One priest seen covered in blood on day of murder Police cleared suspects using wrong DNA

The ABC's Trace podcast has been reinvestigating the murder for over a year, and recently became aware that an incorrect DNA sample had been used to rule out persons of interest in the case.

On presenting that information to authorities, the ABC was issued a statement by Victoria Police stating it had discovered "an error in the handling of an exhibit".

"The exhibit in question had been forensically tested and used to eliminate suspects. A recent review by the homicide squad however has shown that the exhibit was in fact unrelated to the Maria James case," the statement said.

"A small number of persons of interest who had previously been eliminated will now be re-assessed in accordance with normal investigation procedures.

"Victoria Police would like to stress that this was an isolated human error, and not the result of any flaws in the forensic testing process."

'I'm devastated by this information'

For nearly four decades, police have failed to identify Maria James' killer.

In 2013, it was revealed Father Bongiorno sexually abused her 11-year-old son Adam, who has cerebral palsy and Tourette syndrome, in the weeks prior to her murder.

Now 48, Adam said he told his mum of the abuse and believed she planned to confront the priest.

Father Bongiorno died in 2002.

Trace also revealed a local electrician working at the nearby St Mary's church said he saw Father Bongiorno with blood on his face, arm and hands on the afternoon of the murder.

The electrician, Allan Hircoe, said he took the information to Victoria Police, but was told it was not pertinent to the Maria James case.

"They just told me that the DNA [they] found at the scene is not [Bongiorno's]," Mr Hircoe said.

"They had the DNA of [Maria James] and other DNA, and they said it's not his."

Police visited Maria's eldest son Mark James on Tuesday night to inform him of their error.

Mark James said he was "shaken up" by the DNA bungle and found it difficult to accept.

"I'm devastated by this information," he told Trace.

"They mentioned I think nine suspects that need to be retested, based on this error, and Father Bongiorno was among them.

Mark James lost his mum when he was 13 years old. ( ABC RN: Jeremy Story Carter )

"They apologised to me for what's happened, and they apologised for previously being told that Father Bongiorno had been eliminated, whereas now they can confirm Bongiorno has not been eliminated through any type of DNA testing.

"I acknowledge human error is a fact of life, but it seems a bit odd that somehow this pillowcase got put into mum's evidence lot."

Family calls on police to reopen investigation

The application to the coroner draws heavily on information reported by Trace. ( ABC RN: Jeremy Story Carter )

In light of the new information, police are hoping the killer's DNA exists on other exhibits from the Thornbury crime scene.

Mark James said he believed police should reinvestigate Father Bongiorno as a key suspect.

He also called for an investigation into Father Thomas O'Keeffe, who was parish priest at St Mary's Thornbury, and once abused Adam James on the same day as Father Bongiorno.

Survivors who had been abused by Father O'Keeffe in other parishes around Melbourne prior to him moving to St Mary's told Trace he was a terrifying and violent "psychopath".

Father O'Keeffe died in 1984, but it is understood police could access familial DNA that would establish a DNA profile for him.

This could then be compared against any newly created DNA profile of the killer.

Victoria Police said they were committed to achieving justice for the family of Maria James, but would not comment further on the case.

"My brother was sexually assaulted by both Bongiorno and O'Keeffe right before my mum was killed," Mark James said.

"My mum found out about it. She had contact with the church, where that contact indicated she was going to complain, and within a matter of a day or two, she's murdered under very mysterious circumstances.

"I think this merits reopening."