A medical expert testifying at an inquiry into serial killer Kathleen Folbigg's convictions has been quizzed on whether a report he authored on smothering cases contained "selection bias".
A second judicial inquiry is looking at Folbigg's convictions for killing her four babies - Laura, Sarah, Caleb and Patrick - between 1989 and 1999.
Folbigg,55, and her two daughters, Laura and Sarah, were later found to carry a rare genetic variant known as CALM2-G114R, leading to the current inquiry.
On Friday, Stephen Cordner, the author of a report which concluded there was nothing from a forensic pathology viewpoint to suggest the children had been killed, was probed on the statistical underpinnings of a review he undertook on smothering cases.
Professor Cordner was questioned about whether his conclusions in the review were "skewed" by selection bias due to the omission of smotherings not established to be intentional.
He stood by the work, saying of the methodology: "If they're not established to be intentional, then we can't say they're intentional smothering, and what we're trying to get to in this matter, I believe, is whether or not the four Folbigg children can be said to have been intentionally smothered".
Tom Bathurst KC, who is helming the inquiry, described the line of questioning as an attempt to "undermine the statistical basis on which Dr Cordner has made his report".
Prof Cordner conceded that he left out the term "suffocation" from his review, but denied it was out of a concern of skewing the results.
"I just didn't use it, I think I was so focused on smothering, that's what this matter has been all about," he said.
"I know that other people have been using the word suffocation to mean smothering, but to my mind what we were focused on what smothering.
"I do accept that I would have liked to include that word in retrospect."
Earlier this week, federal independent MP Monique Ryan, a paediatric neurologist, told the inquiry Folbigg's son Patrick may have died in 1991 from an undiagnosed neurogenetic disorder.
The inquiry, which is in its second block of public hearings, is probing cardiac and genetic evidence as well as psychology, psychiatry and evidence relevant to Folbigg's diaries.
Folbigg was sentenced in 2003 to 40 years in prison, but that was reduced on appeal to 30 years, with a non-parole period of 25 years.
Folbigg maintains her innocence, claiming all four children died of natural causes.
She will be eligible for parole in 2028.
The inquiry continues.
