Jailed in 2003 and considered at the time to be Australia’s most prolific female serial killer, Kathleen Folbigg has now been pardoned over the death of her four children and will be released without delay.

Folbigg, 55, was convicted of killing her three children Patrick, Sarah and Laura, and was also found guilty of the manslaughter of her firstborn Caleb between 1989 to 1999.

Her babies were aged between 19 days and 19 months.

The historic convictions have not been quashed as that can only be done through the Court of Criminal Appeal.

Folbigg has always maintained her innocence, insisting that her children had each died of natural causes, and as a result she has served 20 years of a minimum 25-year prison sentence.

NSW Attorney General Michael Daley announced the pardon, saying Folbigg had endured “a terrible ordeal” and there was a possibility she could sue the government if the convictions were quashed, a legal step which goes beyond a pardon.

“What is the difference between today and what has transpired in the past? New evidence has come to light,” he said, referring to new scientific evidence submitted in an inquiry into the death of the babies.

Former NSW Chief Justice Tom Bathurst KC is leading the inquiry and is now writing up a final report for the NSW governor.

Daley said he had received a phone from Chief Justice Bathurst last week that “he had come to a firm view” about what the outcome of his report would be.

Prosecutors argued Folbigg smothered her children during periods of frustration and insisted that some of her diary entries were admissions of guilt.

New scientific evidence has now cast sufficient doubt on her guilt.

Folbigg and her two daughters were found to carry a rare genetic variant, CALM2-G114R, which can cause cardiac arrhythmia and sudden death.

According to cardiology and genetic experts, the genetic verity was a “reasonably possible cause” of Sarah and Laura’s death.

The variant was not found in Caleb or Patrick.

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This article first appeared on Over60.