Kathleen Folbigg appears via video link at the NSW Coroners Court. Picture: AAP
Kathleen Folbigg appears via video link at the NSW Coroners Court. Picture: AAP

The medical discovery that could exonerate child killer

The discovery of a new gene mutation could explain cases of sudden infant death and poke holes in one of the country's biggest murder investigations.

Breakthrough research has found a mutation in the heart could be responsible for the deaths in the late 1990s of the Folbigg children, whose mother, Kathleen, was convicted in NSW in 2003 of the murder and manslaughter of Caleb, Patrick, Sarah and Laura

The "G114R" mutation, in the CALM2 gene, was first found in 2018 after Australian National University Professor Carola Vinuesa, used genome sequencing on Folbigg as part of the infamous Australian case.

Folbigg was convicted in 2003 in New South Wales for the murder and manslaughter of her four children - Caleb, Patrick, Sarah, and Laura. She is over halfway through a 30-year prison sentence and has always maintained her innocence.

But questions have now been raised after the findings, published on Saturday in the Oxford journal EP Europace, showed both Folbigg and her two daughters had the mutation.

More importantly, the extensive international research concluded the CALM2 mutation was the "likely" cause for the two girls' deaths.

"Once you have one of these mutations in the family, they tend to be dominant," Prof Vinuesa told the Herald Sun.

"And now we know that CALM mutations can cause deaths from weeks of age until adulthood.

"What we have found is the CALM2 variant was the likely cause for the deaths the two Folbigg girls, Sarah and Laura."

The medical breakthrough also means previously unexplained cases of SIDS could be determined and even prevented.

CALM genes have also been linked to a number of deadly arrhythmia problems which fail to show up on a regular ECG scan.

The mutation causes irregularities with the heartbeat that can be potentially fatal.

The new research found this to be as severe as other similar arrhythmia-causing mutations that cause sudden unexpected death of infants and children while awake or asleep.

It can also be triggered by stress and possibly from infection, which both girls reportedly had at the time of their death.

Kathleen Folbigg appearing at an inquiry into the death of her children. Picture: AAP
Kathleen Folbigg appearing at an inquiry into the death of her children. Picture: AAP

The gene is inherited from the mother, and more recent findings have shown more than 13 per cent of carriers of the lethal mutation remain healthy.

This means while Ms Folbigg is medically fine, the mutation could have been deadly to her children.

Further genetic work has shown that the two Folbigg boys - who had medical issues - carried a different mutation, in a gene which when deleted has been shown to cause lethal epilepsy in mice.

This has not yet been proven, but Prof Vinuesa and her team believed it was cause for further investigation.

"We need this evidence to be able to conclude if it could have contributed to the cause," she said.

"But their presence highlights that there could be two different causes of death."

Prof Vinuesa and co-author Professor Matthew Cook, also from ANU, were independently asked to investigate the genomics of the case for the 2019 Folbigg inquiry.

The inquiry finished that year, before the most recent results being published, and concluded there was no natural cause for the Folbigg children's deaths.