Kathleen Folbigg has been pardoned over the death of her four children and released without delay, after new scientific evidence raised doubts over her guilt.
Folbigg, 55, was convicted of killing her three children Patrick, Sarah and Laura as well as the manslaughter of her firstborn, Caleb, between 1989 to 1999.
Her babies were aged between 19 days and 19 months.
The convictions, which resulted in her being jailed for 20 years, have not been quashed as that can only be done through the Court of Criminal Appeal.
Folbigg has always maintained her innocence saying her children all died of natural causes, and she has served 20 years of a minimum 25-year prison sentence.
Announcing the pardon, NSW Attorney General Michael Daley said Folbigg had endured "a terrible ordeal" and there was the possibility she could sue the government if the convictions were quashed, a legal move which goes beyond a pardon.
"What is the difference between today and what has transpired in the past? New evidence has come to light," Daley said, alluding to genetic scientific evidence which was presented in an inquiry into the death of the babies.
Former NSW chief justice Tom Bathurst KC, the head of the inquiry, is preparing a final report for the NSW governor. That report could be finished this month.
In a memorandum outlining his findings, which was sent to Daley on Friday, Bathurst stated he had reached "a firm view that there was reasonable doubt as to the guilt of Ms Folbigg for each of the offences for which she was originally tried."
Key points in the memorandum which led to the pardon decision included "the reasonable possibility" that three of the children died of natural causes, and that in the case of Sarah and Laura there was "a reasonable possibility a genetic mutation known as CALM2-G114R occasioned their deaths".
In the memorandum, Bathurst was "unable to accept… the proposition that Ms Folbigg was anything but a caring mother for her children".
Diary entry murder theories thrown out
Prosecutors argued Folbigg smothered her children during periods of frustration and asserted that some of her diary entries were admissions of guilt, a theory which today was discredited.
The diary entries, the memorandum said, "were the writings of a grieving and possibly depressed mother, blaming herself for the death of each child, as distinct from admissions that she murdered or otherwise harmed them".
New genetic evidence cast doubt on Folbigg's guilt and paved the way for her pardon.
Folbigg and her two daughters were found to carry a rare genetic variant, CALM2-G114R, which can cause cardiac arrhythmia and sudden death.
The genetic variant was a "reasonably possible cause" of Sarah and Laura's deaths, according to cardiology and genetics experts.
The variant was not found in Caleb or Patrick.
Crucial phone call
Last Tuesday Bathurst had telephoned Daley and the pair spent some time talking about the report and the conclusions it was drawing.
Bathurst indicated he was making substantial progress on the draft, but he'd already "come to a firm view" about what the outcome of the report would be, Daley said.
"He asked me if I would find it useful, or if it would assist, for him to send me in advance of his report his preliminary findings," he said.
"I told him I would find it very useful indeed and that would assist us all greatly."
Daley read a memorandum, mailed on Friday, which contained "very clear" reasons to pardon Folbigg.
"As you would expect over the weekend, I sought the appropriate advice and weighed up the options available to me very carefully."
Daley concluded Folbigg should be released from custody as soon as possible.
At 9.30am, Daley met with the governor, and the pardon was agreed.
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