The family of murder victim Maria James is calling for the coroner to investigate whether collusion within Victoria Police contributed to a major DNA bungle that derailed the cold case investigation into her death.
The single mother was brutally stabbed 68 times in the back of her Thornbury bookshop in 1980, by someone police believe was known to her. Her murder has remained unsolved for 37 years.
In the wake of the ABC's Trace podcast investigation, Victoria Police admitted they used a pillow from an entirely separate crime scene to create a DNA profile of the killer in James' murder.
That profile was then used to rule out a number of suspects, including paedophile priest Father Anthony Bongiorno, who sexually abused James' son Adam and was seen near the crime scene covered in blood.
Victoria Police Assistant Commissioner Steve Fontana described the mix-up as embarrassing, but insisted it was a case of human error.
But Maria's eldest son Mark James said he wants the Victorian coroner, who is currently deciding whether to formally reopen the case, to consider the possibility that the DNA bungle did not occur by accident.
"I can't exclude the possibility that in the past, a conspiracy had occurred," Mark James told Trace.
"The Catholic Church has been accused of covering things up so I can't exclude the possibility that there was some type of a cover-up."
Quilt from crime scene has gone missing
In addition to having a pillow from a separate crime scene wrongly incorporated into the evidence in the case, Mr James believes a potentially crucial piece of evidence might now have gone missing.
He has been told by police that the contents of an evidence bag labelled "quilt" have been removed.
"Somehow the quilt has been taken out of that bag and this pillow from another case altogether has been substituted in that bag," Mr James said.
"Victoria Police at this stage appear to have lost it. They don't know where the quilt is."
Since becoming aware of the DNA mix-up, Victoria Police has maintained it was the result of an internal error and had "nothing to do with the Catholic Church".
Victoria Police declined to comment to Trace, but have previously said they are committed to retesting exhibits to establish an accurate profile of the suspected killer.
Police-church collusion 'has happened before'
Former police officer Denis Ryan says his career was ruined by collusion between the church and the police force, through the interference of the so-called Catholic Mafia within Victoria Police.
In 1971, Mr Ryan learnt of numerous allegations of horrific abuse by the assistant priest of a regional Victorian parish in Mildura, Monsignor John Day.
His efforts to investigate the paedophile priest were thwarted by senior members within the police force.
"The conspiracy that went on in my time is a major conspiracy and it engulfed the highest ranking officer in the police force down," Mr Ryan told Trace.
Mr Ryan was effectively forced to resign as a police officer in 1972.
He received a formal apology from Victoria Police following his evidence at the Royal Commission into Institutional Responses to Child Sexual Abuse in 2015.
Mr Ryan stressed he could not comment on the Maria James case, as he left the police force eight years before her murder.
Neither he nor the ABC suggests the investigation into Maria James' murder was subject to the same type of conspiracy as occurred in Mildura.
However, he said his story was indicative of the type of collusion possible between the church and the police.
"The Royal Commission has shown and I have shown in my former investigation that they are capable of anything," he said.
"I am a victim of what they can do, and they certainly can do it in the most heinous of all crimes."