“Kathleen is over the moon but will need time to distill the news,” said barrister Isabel Reed who spoke with Folbigg in Cessnock Jail on Tuesday after the announcement.

Ms Reed steered a University of Newcastle Legal Centre team that petitioned the NSW Governor for the inquiry in 2015 after a two-year investigation of the Folbigg case. The investigation focused on the lack of evidence the babies were suffocated and the incidence of three or more baby deaths in the one family from unidentified natural causes.

Lawyers are investigating the possibility of bail for Folbigg, despite Mr Speakman saying she would remain in jail during the inquiry by former Chief Judge of the District Court Reg Blanch that is expected to take up to 12 months.

An emotional John Folbigg, whose brother Craig was married to Kathleen and the father of babies Caleb, Patrick, Sarah and Laura, said the decision to hold an inquiry “almost makes me ill”.

“I haven’t spoken to Craig yet because it’s only just happened. But all I can is I’m frustrated that someone in the position of the Attorney-General could be put under such pressure by a bunch of radicals, with no feeling for the family or the girl in jail,” Mr Folbigg said.

READ MORE: Barrister calls for Folbigg to be released, review of case

“What’s it going to do to Kathleen when they do this inquiry and the outcome’s the same?”

In a statement to the media Mr Speakman said the distress that the decision to hold an inquiry would cause was “something that has weighed on me heavily”.

“This has been an immensely difficult decision. Put yourself in the position of Ms Folbigg’s ex-husband Craig,” Mr Speakman said.

“The worst thing that can happen to anyone in their life is to lose a child. Just imagine what it must be like to lose four children. It has weighed on me. Whatever view you take of this case it is a tragedy beyond imagining that four beautiful children were lost.”

Mr Blanch is required to have particular regard to evidence about the incidence of three or more child deaths in one family from unidentified natural causes.

READ MORE: Monster or miscarriage of justice?

Mr Speakman said he announced the inquiry after forming the view it was necessary to ensure public confidence in the administration of justice.

Ms Reed said Folbigg’s lawyers received a message about the announcement about an hour before it was made and Folbigg’s solicitor advised her of the inquiry while talking to her by phone as it was being announced.

Ms Reed said Mr Speakman’s announcement showed a NSW justice system that was capable of responding to issues where there was evidence of a miscarriage of justice.

“I was 80 per cent confident that there would be an inquiry but there is room for a decision not to be made at all,” Ms Reed said.

“It could have just not happened but I was pretty confident there would be an inquiry. It would have been outrageous if a decision wasn’t made.”

Newcastle barrister Robert Cavanagh last week argued that Folbigg needed to be released from jail for an inquiry into “how a miscarriage of justice occurred”.

“You can’t have a conviction where there’s a natural cause of death and yet that’s what’s occurred here and she’s been in jail for 15 years because of it,” Mr Cavanagh said.

Folbigg was sentenced to 30 years’ jail on appeal, with a 25-year release date for murdering three of her children, and the manslaughter of a fourth, at Singleton between 1989 and 1999.  

Mr Speakman said Mr Blanch could refer the case to the Court of Criminal Appeal if there is a reasonable doubt about Folbigg’s guilt.