New scientific evidence "fundamentally changes" the understanding of the circumstances around the deaths of convicted killer Kathleen Folbigg's daughters, a lawyer for the NSW Director of Public Prosecution (DPP) says.
Retired Chief Justice Tom Bathurst KC is hearing closing submissions after a long-running judicial inquiry into Folbigg's convictions for killing her four children in the New South Wales Hunter region between 1989 and 1999.
Sarah, Laura, Patrick and Caleb, aged between 19 days and 19 months, died on separate occasions and Folbigg has always maintained natural causes were to blame.
Scientists have told the inquiry new evidence suggests a rare gene mutation may have caused the deaths of her daughters Laura and Sarah.
Dean Jordan SC, barrister for the DPP, said the discovery of the gene mutation "fundamentally changes our understanding of the circumstances leading to the deaths of the girls".
Mr Jordan said pathology evidence relevant to the death of each Folbigg child, and expert evidence about the interpretation of Folbigg's diaries, were not available when she stood trial in 2003.
"The most critical new evidence was beyond the contemplation of science when the trial was conducted in 2003," Mr Jordan said.
"The new evidence was not available to courts that dismissed challenges in 2005 and 2007.
"It is important to keep in mind the historical context of what was not known in 2003 at the time of Ms Folbigg's trial."
At trial, Folbigg's diary entries were seen as admissions of guilt, but experts have since argued they were the expressions of a grieving mother.
Mr Jordan said criticisms of judges and appeal processes relevant to the case have been made "with the considerable benefit of hindsight" and should not be accepted.
The inquiry heard the DPP accepts the possibility of reasonable doubt about Folbigg's convictions of three counts of murder and one of manslaughter.
Similarities to Lindy Chamberlain case
It is the strongest indication yet the 55-year-old could be freed from jail before she finishes serving the final five years of her 25-year sentence.
Folbigg's lawyer Robert Cavanagh said she was wrongly convicted, and drew similarities to the Lindy Chamberlain case.
Ms Chamberlain was wrongly convicted of the murder of her daughter Azaria, and was released years later thanks to new evidence.
He said at the time there was significant "public agitation" after the new evidence came to light.
"We have detailed extensively her [Folbigg's] repeated expressions of grief about the loss of her children," Dr Cavanagh said.
"It depends on what evidence is before which court, and inquiry, at what time."
Report to be delivered to Governor
If Mr Bathurst finds reasonable doubt, he could refer the case to the Court of Criminal Appeal to consider quashing Folbigg's convictions.
He has not yet set a date to release his findings, but told the inquiry he will deliver a report to the Governor, Margaret Beazley, as soon as possible.
Mr Bathurst said there was a body of evidence to suggest reasonable possibilities of natural causes of death for the Folbigg children.
In response to comments from Folbigg's lawyer about her difficult childhood, during which her father murdered her mother, Mr Bathurst said he was "not going to make a finding that Ms Folbigg's tragic childhood history predisposed her to kill children".
The inquiry has now finished.
