Kathleen Folbigg to seek biggest compensation in Australian history

Kathleen Folbigg's legal team will be pursuing a record-breaking compensation payout after she spent two decades in prison before her convictions were quashed.

Forensic anthropologist Xanthe Mallett, who has written extensively about the case, said she "wouldn't be surprised" if that figure was upwards of $10 million.

"If you look at what she's had to suffer in terms of vilification, the psychological impact ... she's been labelled as Australia's worst female serial killer," she said. 

"This is so egregious that I think there needs to be a very significant payment, because there's been many opportunities through the years to see this set right."

Lawyer Rhanee Rego confirmed outside the NSW Court of Criminal Appeal on Thursday that they would soon be seeking a substantial figure for their client. 

"It will be bigger than any substantial payment that has ever been made before," she said. 

Ms Folbigg always maintained she never killed her four young children Caleb, Patrick, Laura and Sarah Folbigg.

All were babies or toddlers when they died between the years of 1989 and 1999 in the Hunter region.

Ms Folbigg was convicted over all four deaths, and sentenced to 30 years in prison, with a non-parole period of 25 years. 

She served 20 of those years before a landmark Special Commission of Inquiry found reasonable doubt over her guilt. 

New scientific and medical evidence surrounding a rare genetic condition was presented to retired chief justice Tom Bathurst KC, who led the inquiry. 

The inquiry heard the medical evidence could explain the deaths of three of Ms Folbigg's children.

It heard a genetic condition could have caused the deaths of Sarah and Laura, while other evidence found that an underlying neurogenetic epilepsy could have caused Patrick's death.

NSW Treasurer Daniel Mookhey flagged that his government would respectfully engage with Ms Folbigg throughout the compensation process.

But Dr Mallett pointed out that no state or territory in Australia, besides the ACT, is obliged to offer what is known as the ex gratia payment. 

"And if they choose not to do so, then there's no way to complain about that lack of compensation," Dr Mallet said. 

"In essence, it's a way of them making a payment, but without accepting any kind of responsibility."

Dr Mallett pointed to South Australian Henry Keogh, who spent 19 years in prison after he was wrongfully convicted for his fiance's murder. 

He received $2.5 million. 

"And in that case, there was clear forensic evidence that somebody else had perpetrated that crime that was ignored by the police," Dr Mallett said. 

"And eventually it was that evidence that led to him being found not guilty."

Indigenous Australian Terry Irving spent four-and-a-half years in prison for a bank robbery he was later found not to have committed, 25 years ago. 

"And he's still waiting for compensation. And there's been no explanation as to why that hasn't been provided," Dr Mallett said. 

"There's very little protection for those who have been wrongfully convicted."

The Australian Academy of Science chief executive Anna-Maria Arabia, said the case echoes another famous wrongful imprisonment, Lindy Chamberlain. 

She was serving a life sentence for the murder of her nine-week-old daughter, but her conviction was also quashed when new evidence came to light. 

She received $1.3 million from the federal government in 1992, after spending four years in jail.