THERE is reasonable doubt Kathleen Folbigg is guilty of killing her four children, says the senior barrister assisting an inquiry into her convictions.
"On the whole of the body of evidence before this inquiry there is a reasonable doubt as to Ms Folbigg's guilt," Sophie Callan SC said, summarising her closing submissions on Wednesday.
Former NSW chief justice Tom Bathurst KC is heading the inquiry, triggered by a petition from scientists.
Mr Bathurst will prepare a report for the governor on whether to exercise the royal prerogative of mercy, a power the Department of Communities and Justice describes as "rare and exceptional".
Folbigg's case is similarly rare and exceptional.
She was jailed in 2003 for killing her four children and is serving a 25-year minimum sentence after being found guilty of three counts of murder and one of manslaughter.
Ms Callan said the case against Folbigg remains circumstantial, not to be looked at in a "piecemeal fashion".
Folbigg maintains her innocence, claiming her four babies - Laura, Sarah, Caleb and Patrick - died of natural causes between 1989 and 1999. Folbigg and her two daughters were later found to carry a rare genetic variant, casting doubt on her convictions and triggering the inquiry, the second into her convictions.
The CALM2-G114R genetic variant impacting the calcium-binding calmodulin protein, identified in Folbigg and her two daughters, was a "reasonably possible cause" of Sarah and Laura's deaths according to cardiology and genetics experts.
Myocarditis, an inflammation of the heart, was also a reasonable possible cause of Laura's death.
"Persuasive expert evidence" submitted Patrick may have died from an underlying neurogenetic disorder such as epilepsy, which may have also caused an apparent life-threatening event that hospitalised him before his death, Ms Callan said.
Reasonable hypotheses on the deaths of those three children undermines the tendency reasoning used to convict Folbigg of Caleb's manslaughter.
"The cause of Caleb's death at 19 days remains undetermined," Ms Callan said.
It is possible, but extremely unlikely, a woman could smother her four children without leaving any signs, she said.
Journal entries used at Folbigg's trial contained certain entries that could be interpreted as admissions, however expert psychological evidence "uniformly indicates that it would be unreliable to interpret the entries in this way".
Guilt and self-blame were typical for someone suffering a major depressive disorder and "maternal grief" after the successive deaths of their children, Ms Callan said. "This casts Ms Folbigg's expressions of guilt and responsibility for the deaths of her children in her diary and journal entries in a very different light."
Other submissions to the inquiry argued there were compelling reasons to continue treating the entries as admissions of guilt, but overall, the evidence undermined the probative value of the journal entries, tending to render them neutral, she said.
The Director of Public Prosecutions accepts it is open to the inquiry to conclude there was a reasonable doubt about Folbigg's guilt, Ms Callan said.
"Does that mean I ignore the fact the jury, on the evidence before them, found Ms Folbigg guilty?" Mr Bathurst asked.
New, further, and additional evidence has emerged at the inquiry and "altered the balance" since then, Ms Callan said.
Submissions on Folbigg's behalf urged Mr Bathurst to go as far as finding "a strong probability" she is innocent.
The submission differed from counsel assisting however contained some common ground regarding the new evidence, Ms Callan said. The inquiry continues.
