Pardoned, freed and now acquitted, Kathleen Folbigg’s name has been cleared over the deaths of her four children.

After spending more than two decades in jail over the deaths of her four children before being pardoned and freed, Kathleen Folbigg has now been acquitted.

The NSW Court of Criminal Appeal quashed her convictions on Thursday morning as applause filled the court.

The 56-year-old was granted an unconditional pardon and released from jail in June after an inquiry heard there was reasonable doubt about her guilt following new scientific discoveries.

In a final report released in November, inquiry commissioner Tom Bathurst KC found there was an “identifiable cause” for three of the deaths and Folbigg’s relationship with her children did not support the case that she killed them.

The report was sent to the appeal court.

“While the verdicts at trial were reasonably open on the evidence available, there is now reasonable doubt as to Ms Folbigg’s guilt,” NSW Chief Justice Andrew Bell said on Thursday.

New evidence emerged that Kathleen Folbigg's children had died of natural causes. Photo / AP

“It is appropriate Ms Folbigg’s convictions … be quashed.”

The appeal judges agreed with Mr Bathurst’s finding that the mother’s diary entries - controversially used during her trial to help secure her convictions - did not contain reliable admissions of guilt.

Folbigg consistently told police and a previous inquiry the entries reflected her feelings of failure as a mother after the deaths of three of her children.

She was convicted in 2003 and ordered to serve a minimum 25-year sentence for the suffocation murders of three of her children and manslaughter of a fourth.

The children, Caleb, Patrick, Sarah and Laura, died between 1989 and 1999 at ages ranging from 19 days to 18 months.

“(I) grieve for my children and I miss them and love them terribly,” Folbigg said in a video following her release in June.

A rare genetic variation was a “reasonably possible cause” of Sarah and Laura’s deaths, according to cardiology and genetics experts.

Myocarditis, an inflammation of the heart, was another possible cause of Laura’s death.

Patrick may have died from a neurogenetic disorder, which could have also hospitalised him before his death, experts told the inquiry.

Reasonable causes for their deaths undermined the tendency reasoning used to convict Folbigg of Caleb’s manslaughter.

Folbigg’s lawyers have previously indicated the possibility of seeking compensation from the state.