Kathleen Megan Folbigg, who was found guilty of killing her four babies in the decade from 1989, will give evidence related to her personal diary entries at a Sydney inquiry into her convictions.

Folbigg was jailed for at least 25 years in 2003. The four children – Caleb, Patrick, Sarah and Laura – all died aged between 19 days and 19 months.

A hearing into her convictions began at Lidcombe coroner’s court on Monday after the New South Wales government agreed to a judicial review of her case in August 2018.

“Ms Folbigg is allowed to give evidence, if she wishes to do so, about the diary entries, possession of the diaries and her disposal of the diaries,” the counsel assisting, Gail Furness SC, said in her opening address.

Folbigg’s evidence and cross-examination will be restricted to those issues, with 17 and 18 April set aside for her to testify, which the 51-year-old has confirmed in writing.

Furness cited various diary entries by Folbigg which were presented to the trial jury as circumstantial evidence.

These included comments about baby Sarah who “left, with a bit of help” and Laura being “a fairly good-natured baby” which “saved her from the fate of her siblings”.

“I think she was warned,” Folbigg wrote in December 1997.

Laura, her fourth child, died in March 1999.

The inquiry will focus on medical advances and new research, including on multiple infant deaths in the one family attributed to unidentified natural causes.

The crown prosecutor in 2003 submitted “it has never been recorded that the same person has been hit by lightning four times” and “I can’t disprove that one day some piglets might be born with wings and that they might fly. Is that reasonable doubt?”

The judge directed the jury that sudden infant death syndrome (SIDS) deaths were rare and while there was no authenticated record of three or more such deaths in a single family, it did not mean such events were impossible.

Professor Rosemary Horne on Monday testified Sids itself was rare but “the general consensus seems to be that more than one Sids in a family is very rare”.

“I have asked my colleagues … in the UK and USA and none of them could recall having three or more deaths in a family,” the Monash university paediatric researcher said.

Both she and Professor Dawn Elder, who heads paediatrics at New Zealand’s University of Otago, gave evidence that all four of Folbigg’s children had a low risk of Sids.

The former NSW district court chief judge Reginald Blanch QC is presiding over the 2019 inquiry. He will prepare a report on its results for the governor of NSW.

If the judicial officer feels there’s reasonable doubt over Folbigg’s guilt he can refer the matter to the court of criminal appeal.

Folbigg will, at present, be eligible for parole in April 2028. The inquiry continues.