Advances in medical sciences could help answer questions about the evidence used to convict serial killer Kathleen Folbigg, amid suggestions the deaths of her four children could be explained by natural causes.

Key points: The inquiry examining the new forensic evidence would not be launched until February or March next year

The inquiry examining the new forensic evidence would not be launched until February or March next year Senior counsel said the jury was "certainly misled" by experts on the rarity of SIDS

Senior counsel said the jury was "certainly misled" by experts on the rarity of SIDS A report from a clinical psychologist said Kathleen Folbigg's diary did not contain a clear admission of guilt

Ms Folbigg was sentenced to a minimum of 25 years in prison in New South Wales after being found guilty in 2003 of the murder of three of her infants and the manslaughter of a fourth over a 10-year period from 1989.

She has always maintained her innocence.

At today's directions hearing, former chief District Court judge Reginald Blanch QC said an inquiry, unlikely to begin until February or March next year, would examine new evidence from forensic pathologists.

Senior counsel assisting the inquiry Gail Furness told the hearing the convictions were based on circumstantial evidence and four new reports from medical experts suggest the deaths could be explained by unidentified natural causes.

"Three of the reports concern the cause of the deaths and one is addressed to the use of diary evidence. None of those authors gave evidence at the trial," Ms Furness said.

(Clockwise from top left) Patrick, Laura, Caleb and Sarah Folbigg, who were killed (manslaughter for Caleb, murder for Patrick, Laura and Sarah) by their mother Kathleen Folbigg in the NSW Hunter Valley. ( ABC News )

The main report expected to be relied upon, by Monash University forensic pathologist Professor Stephen Cordner, concluded "there is nothing from a forensic pathology viewpoint to suggest that any of the children had been killed".

Ms Furness said the report by Mr Cordner indicated there were natural causes of death for two of the children, Patrick and Laura, and natural causes were a plausible explanation for the other two deaths, Caleb and Sarah.

A peer-reviewed report on his work, which will also be examined, suggested the "jury was almost certainly misled by statement made by experts regarding the rarity of multiple cases of SIDS [sudden infant death syndrome]".

A report from a clinical psychologists suggested Ms Folbigg's diary entries, which were crucial to the prosecution argument against her, did not contain a clear admission of guilt.

However, Ms Furness said the report did not generate enough doubt to warrant further examination of the diary entries.

Instead, the scope of the inquiry will focus on medical evidence in light of any new material to have emerged since 2003.

Outside court, barrister Isabel Reed, who has been one of a number of lawyers working on the review, said her client was "as well as could be expected".

A senior counsel is yet to be appointed to represent Ms Folbigg at the inquiry.