Genetic variants identified in Kathleen Folbigg and her two daughters were not discovered until nine years after she was convicted of killing her four children.

An inquiry into her conviction has heard from two Danish scientists about the calcium-binding protein calmodulin, an early building block of life.

“It was regarded in the scientific community up until 2012 that variations in calmodulin were incompatible with life,” professor Michael Toft Overgaard told the inquiry being conducted by former NSW chief justice Tom Bathurst KC on Tuesday.

A study led by professor Mette Nyegaard, appearing alongside Professor Overgaard, identified variants in a large Swedish family, surprising the scientific community.

“There was a clear pattern … we identified the first variant in calmodulin, really ever seen,” Professor Nyegaard said.

She said the discovery was “extremely surprising”.

Three different genes in the human genome produce calmodulin.

The inquiry on Monday heard the variant identified in Folbigg, specifically CALM2 G114R, can affect the electrical activity of the heart.

Professor Overgaard said that variant was recently analysed.

“There’s a significant impact on how calmodulin can bind to the [cardiac ion] channel,” he said.

Mr Bathurst is being asked to form his own view on whether there is any reasonable doubt about Folbigg’s guilt.

The inquiry comes 19 years after Folbigg was sentenced for the murder of three of her children and the manslaughter of a fourth, and three years after a separate inquiry.

The children, born separately between 1989 and 1997, were aged between 19 days and 18 months old when they died.

Folbigg was charged in April 2001.

The NSW Governor has ordered the re-examination following a petition from scientists calling for an inquiry due to new evidence.

The variant CALM2 G114R, is “exceptionally rare”, associate professor Hariharan Raju told Monday’s hearing.

“Overall, I still feel she doesn’t have sufficient data to confirm a diagnosis,” Professor Raju said, noting Folbigg did have some minor cardiac abnormalities.

“When I consulted with her [in 2019], although the DNA variant had been identified, it wasn’t clear at that point whether it was responsible for any disease at all,” he said.

Folbigg was sentenced to 40 years in prison, which was reduced on appeal to 30 years with a non-parole period of 25.

She is not eligible for parole until 2028.

The hearing continues.

– AAP