A rare genetic variation found in two of Kathleen Folbigg’s children could lead to the convicted baby killer being pardoned and freed from jail after 19 years, an Australian inquiry has been told.

An inquiry examining the death of Folbigg’s four children and advances in scientific research into rare genetic mutations has begun in Sydney.

Folbigg, 55, is serving a 30-year prison sentence after she was convicted of three counts of murder and one count of manslaughter over the death of her children Patrick, Sarah, Laura and Caleb, who all died in suspicious circumstances between 1989 and 1999.

She has been in jail since 2003 but consistently denied any wrongdoing and has launched two unsuccessful appeals before a public inquiry in 2019 again reinforced her guilt.

But last year, new expert medical evidence, which showed that Sarah and Laura Folbigg carried a genetic mutation that could cause cardiac problems, led to renewed calls for her to be pardoned.

Her supporters have argued that the CALM2 G114R genetic variation found in two of her children can lead to cardiac arrhythmia and death.

The inquiry, being heard by retired New South Wales Supreme Court Justice Tom Bathurst, will produce a report to be sent to the governor, who could decide to exercise “mercy” or pardon Folbigg.

Alternatively, if it’s found there is reasonable doubt as to her guilt, the matter can be referred to the Court of Criminal Appeal to decide whether her convictions ought to be quashed.

During Folbigg’s trial, the prosecution argued that she killed her four children by smothering them, but she said they died of natural causes.

Each of the children died in the family’s Newcastle home and was discovered by Folbigg while they were thought to be asleep.

They were aged between 19 days and 18 months when they died.

“No expert is expected to tell Your Honour that the CALM variant definitely caused the death of either Sarah or Laura Folbigg,” counsel assisting the inquiry Sophie Callan, SC, said during her opening address on Monday morning.

 “Equally, no expert is expected to tell your honour that the CALM2 variant could not have possibly caused their death.

“Rather the experts divide in that middle ground in terms of the likelihood this novel genetic variant could have had any role to play in their deaths.”

The genetic variant, which Folbigg was found to have passed to her daughters, was not detected in Caleb or Patrick Folbigg.

Folbigg’s barrister, Gregory Woods, KC, told the court that it could not be “properly excluded” that the girls’ deaths were caused by the CALM2 G114R mutation.

He also pointed to a report by Professor Peter Schwartz, who is due to give evidence to the inquiry next week, that said the variants could not be ruled out as contributing to the death of Folbigg’s two daughters.

“The deaths of Laura and Sarah Folbigg are fully compatible with their CALM mutation,” Schwartz said in his report, the inquiry was told.

“There is not a single scientific element to prove the contrary … If any infant or child dies suddenly, the post-mortem is negative and a CALM mutation is found, the diagnosis would be sudden death due to calmodulin mutation. End of story.”

Folbigg will not give evidence before the inquiry and is watching proceedings via videolink from prison at Clarence Valley Correctional Centre.

The inquiry heard that Folbigg had reported to a cardiologist, Professor Hariharan Raju, that she had suffered recurring episodes of fainting since childhood which were associated with exercise, stress and pregnancy.

Raju told the inquiry that he had carried out an ECG (electrocardiogram) and cardiac stress test on Folbigg but they were “normal”.

However, he told the inquiry that did not diminish the findings of the scientific journal article, that two of the children’s deaths could be explainable by natural causes.

“There are multiple explanations why an individual who carries an identical genetic risk may have an absence or difference in severity, or difference in expression, of the disease,” Raju said.

The inquiry continues on Tuesday.