An inquiry into Kathleen Folbigg’s convictions for the deaths of her four children has heard a “reasonable hypothesis” could cast doubt on her guilt.

Experts are expected to give conflicting evidence on newly identified genetic variants and her diaries used at trial.

Folbigg was convicted in 2003 for the manslaughter of her son Caleb, and the murder of her other son Patrick and two daughters Sarah and Laura.

The children died separately over a decade, aged between 19 days and 18 months old.

Folbigg’s convictions were subject to an inquiry conducted by former NSW District Court chief judge Reg Blanch in July 2019 which concluded her guilt was “even more certain”.

NSW Governor Margaret Beazley ordered a fresh inquiry in May following a petition from scientists after the emergence of new evidence around genetic variants identified in Folbigg and her children.

Former chief justice Tom Bathurst KC has been tasked with forming a view about whether there is any reasonable doubt about Folbigg’s guilt.

Professors Mette Nyegaard and Michael Toft Overgaard, two Danish researchers who first made the “extremely surprising” discovery that genetic variants could effect production of the calcium-binding protein calmodulin, previously told the inquiry it was likely the genetic mutation could have caused the death of Sarah and Laura.

The inquiry sat for two days in November and resumed on Monday.

Counsel assisting the inquiry, Sophie Callan SC, said other genetic experts giving evidence this week will tell the inquiry the variant identified in Folbigg and her two daughters could be a likely cause of infant deaths.

All four children, but not their mother, also carried another genetic variant, identified in 2018, which could be an aggravating factor in cardiac death, experts will tell the inquiry.

Cardiovascular experts will raise doubts about the calmodulin-affecting variant’s ability to cause disease or death, and its significance.

“The fact a carrier, Kathleen Folbigg, is alive and healthy suggests it is benign,” Ms Callan said on Monday, summarising the expected expert evidence.

She said no witness is expected to give definitive evidence about the causes of death and Mr Bathurst will have to exercise judgment.

“There’s, even on this evidence, whichever way you look at it, a reasonable hypothesis inconsistent with guilt?” Mr Bathurst asked the counsel assisting.

“Yes Your Honour, in my submission that is the effect of the evidence,” Ms Callan said.

The Danish researchers returned to give further evidence on Monday, addressing some issues identified by other experts yet to appear.

Professor Overgaard said there had been “some reluctance” from others to rely on their analysis conducted in November, however the pair have not altered their previously expressed opinions.

Professor Nyegaard said another witness had miscited past work, where a variant was identified in one patient, and its link to a disease verified through a separate patient.

“This is kind of the gold standard with genetic studies so I think he just maybe didn’t read the full paper,” Professor Nyegaard said.

The inquiry will also consider Folbigg’s diaries, which Ms Callan said were relied upon at her trial as admissions of guilt.

“(Folbigg) squarely challenges that characterisation,” Ms Callan said.

Experts will give evidence the content of Folbigg’s diaries could be explained by complex PTSD and other mood disorders, however not all of them agree she satisfies the criteria for diagnosis.

Folbigg was originally 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.

-AAP