Kathleen Folbigg has been convicted of killing her children. But is she our next Lindy Chamberlain?

Kathleen Folbigg has held the title of "Australia's 'most hated woman'" and "Australia's worst female serial killer" for nearly two decades now.

She was sentenced to 40 years in prison in 2003 for killing her four children, Caleb, Laura, Sarah and Patrick, all before they turned two.

The murders took place between 1989 and 1999 and it was Kathleen's personal diary that helped put her behind bars. 

But now, a second inquiry into her conviction is underway in a Sydney court, as 151 scientists call for her immediate release and within weeks, Folbigg will learn if there was "reasonable doubt", that could lead to a pardon.

On True Crime Conversations this week we unpack all the evidence. Post continues.

The case shares similarities to the story of Lindy Chamberlain, who spent three years in prison after she was falsely convicted of killing her newborn daughter Azaria in 1980. 

The difference here is that Folbigg has spent much, much longer locked away.

The deaths of Caleb, Patrick, Sarah and Laura. 

In February 1989, Caleb Gibson Folbigg was found dead in his cot at just 19 days old. 

He was the first child of Kathleen Folbigg and her husband Craig Gibson Folbigg, and was born with a number of breathing difficulties. His death was originally attributed to Sudden Infant Death Syndrome (SIDS), and a previous diagnosis by a paediatrician of laryngomalacia - “floppy larynx” - was noted pre-mortem.

A little over a year later in October 1990, Patrick Allen Folbigg was found in his cot not breathing. Craig awoke to the sounds of Kathleen screaming and their young son was rushed to hospital. He survived, but went on to be diagnosed with epilepsy and cortical blindness and died at just eight months old in 1991.

His death was also originally attributed to SIDS.

Kathleen and Craig's four children. Image: Australian Story.

Sarah Kathleen Folbigg was born on 14 October 1992, and died during the night in August 1993, at just ten months old. She was also born with breathing problems, and her death was attributed to SIDS. 

In February 1999, Kathleen and Craig's fourth child Laura Elizabeth Folbigg died aged 18 months. It was only after this death that questions started being asked.

Laura's death was ruled as undetermined and a police investigation was ordered.

The 'incriminating' diaries and murder charges. 

It was a grieving Craig Folbigg who discovered Kathleen's diaries after the couple split and she moved out following Laura's death. 

It was the contents of that bedside drawer discovery that prompted a murder investigation, with the diaries forming the prosecution's main evidence against 34-year-old Kathleen at trial. 

The majority of the entries were mundane, the scribblings of an apparently exhausted mother chronicling her daily life and perceptions of parenting. "[The diaries were me] trying to figure out things," Kathleen told ABC's Australian Story in 2018. "[to] understand the un-understandable."

As investigative journalist Jane Hansen told True Crime Conversations in 2022, "what's interesting about that kind of journaling is that, any woman who has lost a child blames themselves. It's very, very common and I've been there myself, one of my sons was stillborn and another I lost at eight months....[and] my diary entries read very similar about 'what a monumental failure I am' and 'if only I hadn't done this', and 'if only I hadn't done that.' 

"In some parts of my diary I talk about karma, because of some things I'd done in my career and maybe this was payback that my son died."

It's since been well documented and researched that when it comes to maternal grief, self blame is standard behaviour. But to prosecutors in 1993, the diaries were alarming.

Kathleen Folbigg's diaries made up a large majority of the evidence that led to her conviction. Image: AAP.

In an entry while pregnant with her daughter Laura in January 1997, Kathleen wrote: “This time I am going to call for help, this time I’ll not attempt to do everything myself any more. I know that that was my main reason for all my stress before and stress made me do terrible things…”

In November that same year, Kathleen wrote: "With Sarah, all I wanted was her to shut up, and one day she did".

A month later, she wrote, "Laura's a fairly good-natured baby, thank goodness. It has saved her from the fate of her siblings. I think she was warned".

Kathleen was charged with murder. During her seven-week trial, the prosecution argued that she had smothered her children to death during periods of frustration.

"All of the medical experts that gave evidence were asked 'have you ever seen a family that's had four sudden infant deaths?'," recalled Hansen. 

 "They all said no, so there was that suspicion and then the pathologist gave his evidence that he'd never seen it before. So there was this idea that if you couldn't find an answer, blame it on the woman," she told True Crime Conversations.

A jury declared her guilty of three counts of murder and one of manslaughter on May 21, 2003, despite there being very little physical forensic evidence to support the prosecution's case against her. 

She was sentenced to 40 years in prison, a sentence which was later reduced to 30 years and then 25 years on appeal. 

She has always maintained her innocence, claiming the four children died from natural causes. 

WATCH: Australian Story: Is Kathleen Folbigg innocent? Post continues after video.

A country divided. 

Kathleen's case had long divided the public, scientific and legal opinion, with many comparing it to the case of Lindy Chamberlain who was jailed for murder after a dingo killed her baby Azaria in 1980. 

Alana House, a former schoolmate of Kathleen’s, wrote for Mamamia in 2012 sharing, "Kathy’s trial had shades of Lindy Chamberlain to it. She was accused of being cold, not showing enough emotion. Like Lindy Chamberlain, people decided she was guilty before the trial even started. Unlike Lindy Chamberlain, most people still hold that opinion…

"People are wrongly convicted all the time. In Kathy’s case, I think there’s reasonable doubt. You don’t throw away the key when there’s reasonable doubt. You make sure an innocent woman isn’t behind bars. Don’t you?"

Kathleen leaving the Supreme Court of NSW in 2003. Kathleen Folbigg is accused of murdering her four children. Image: AAP/Mick Tsikas.

In 2013, 60 Minutes interviewed legal academic Dr Emma Cunliffe about the trial, and in particular, the medical examiner's testimony. 

She said: "There was no positive evidence of homicide in relation to any child," pointing out that the medical experts who had originally ruled that the children died of natural causes "changed their opinion" without any explanation to the court.

But Kathleen's sister Lea Bown, who originally defended her sister, has since accepted her sibling's guilt. 

“I went in there both barrels blasting, calling it a witch-hunt because I just couldn’t believe that anybody could do anything to children,” she told the ABC in 2014.

“It wasn’t really until the trial that I started to say yes she’s done it and it broke me, I just broke when I really realised that she had done it.”

Nicholas Cowdery, who was the New South Wales Director of Public Prosecutions at the time, also believes the jury got it right, telling the ABC in 2018: "There's been an exhaustive process. The case has been assessed by a magistrate, by a jury of 12, which was unanimous in convicting, by the Court of Criminal Appeal, and the High Court has seen nothing to be concerned about in the way in which the convictions have been recorded."

Dr Xanthe Mallett, a trained forensic scientist and criminologist and author of Mothers Who Murder, told Mamamia in 2020, "for each of the child's deaths there were natural causes that were identified postmortem, and each of the children had a medical condition that was pre-diagnosed before death.

"Given there was no evidence on any of the children of physical harm, nor had anyone ever seen her physically harm those children, I do not believe there is evidence beyond reasonable doubt to prove murder. My sense is, if she's guilty she still shouldn't be in prison because the evidence just does not stack up."

The 2019 inquiry that 'reinforced' her guilt.

In 2015, lawyers for Kathleen lodged a petition casting doubt on some of the evidence that led to her conviction. 

Three years later, NSW Attorney-General Mark Speakman announced an inquiry, saying he'd formed the view it was necessary "to ensure public confidence in the administration of justice".

"I don't know why any of my children died, but I didn't kill them," Kathleen told the court during the inquiry. "I didn't kill my children. And these diaries are a record of just how depressed... and [what] a struggle I was having."

Kathleen Folbigg during the 2018/19 inquiry into her case. Image: AAP/Joel Carrett.

The findings of the year long probe acknowledged that while medical evidence alone "neither proves nor disproves that any of the children were smothered",  the inquiry "failed to identify a reasonable natural explanation" for the children's deaths.

"The investigations of the inquiry have instead produced evidence that reinforces Ms Folbigg’s guilt," the report read.

"The only conclusion reasonably open is that somebody intentionally caused harm to the children, and smothering was the obvious method. The evidence pointed to no person other than Ms Folbigg."

2020: The new genetic evidence.

In August 2020, fresh genetic evidence was published in top international cardiology journal, Europace, that raised new questions about the conviction of Kathleen Folbigg. 

In a symposium, Professor Carola Vinuesa, from Australian National University, who is an author on the paper, spoke about the research that was pulled together by an international team of 27 scientists from Australia, Denmark, Italy, Canada, the United States and France.

They found that the Folbigg's daughters inherited a never before reported on genetic mutation from their mother that "likely" caused their deaths. 

The “G114R” variant in the CALM2 gene, which is predicted to cause lethal cardiac arrhythmias, was found in both Laura and Sarah with the paper stating: "A fatal arrhythmic event in both (girls) may have been triggered by their intercurrent infections."

Professor Vinuesa said: "This discovery could help mothers across the globe. Whole genome sequencing has the potential to explain sudden infant deaths."

Professor Carola Vinuesa presented the findings on the Folbigg case last night. Image: Australian Academy of Science/ANU.

A different mutation was found in the Folbigg's sons, that the team suggested could also explain their deaths.

The scientists found that both Caleb and Patrick carry two mutated copies of a gene which, when defective, causes early onset lethal epilepsy in mice. 

Patrick had epilepsy four months before he died. 

In the new report, forensic pathologists declared natural causes of death for the two boys.

Speaking to True Crime Conversations in June 2020, mere months before these findings were published, Dr Mallett said: "What we do know is that once you have one child die from SIDS, you're actually more likely to have another child die of it. That could be environmental, but it could also be genetic, and we just don't understand the causes well enough to be able to understand those links yet. 

"But certainly at the time of the original trial there was evidence available from families in similar to the Folbiggs that looked at multiple deaths within one family and actually showed that this wasn't this unique phenomenon that was painted at trial. There is actually a number of families who do lose multiple children including four siblings."

2021: The fresh push by leading Australian scientists.

In early 2021, 90 eminent scientists submitted a petition to NSW Governor Margaret Beazley, recommending a pardon for Kathleen Folbigg based on the new genetic evidence. 

In April, the Australian Academy of Science offered to brief Mr Speakman on the new findings, but Mr Speakman requested the new evidence be submitted via Ms Folbigg's legal representatives, which occurred in June 2021.

In the August, there was a fresh push by a group of leading Australian scientists. 

Leading Australian scientists have renewed their call for Kathleen Folbigg’s pardon and release from jail.

Read more: https://t.co/lRUM5Q9HxE

— Australian Academy of Science (@Science_Academy) August 30, 2021

Australian Academy of Science President Professor John Shine was amongst the petition signatories.

"The NSW attorney-general now has sufficient medical and scientific evidence before him that provides an alternative explanation for the deaths of the Folbigg children, that carries more weight than the circumstantial evidence used to convict her," he said.

"We urge the NSW attorney-general to expedite this matter and advise the NSW governor to pardon Kathleen Folbigg and release her from jail."

Professor Carola Vinuesa is still clinging to hope the combative arenas of science and law can be united, leading to better understanding and ultimately freedom for Kathleen Folbigg. #60Mins pic.twitter.com/i1xOqtrLYI

— 60 Minutes Australia (@60Mins) August 29, 2021

As of 2022, there are 151 scientists calling for Kathleen Folbigg's conviction to be abandoned, and the pressure has led to a second inquiry currently being held in 2022. 

The genetic evidence is being interrogated, with genetic experts Professors Mette Nyegaard and Michael Toft Overgaard telling the court this week they think it is "likely" that the mutation they've detected caused the deaths of Sarah and Laura. 

The inquiry was due to continue for another week, however has been delayed because of fresh scientific evidence, and will now resume in February. 

Kathleen's life behind bars. 

Kathleen Folbigg has spent the majority of her time behind bars in Sydney's Silverwater prison but was transferred to the Clarence Correctional Centre in Grafton before New Year's Eve.

In a letter to her friend, obtained by The Australian, Folbigg wrote: "In first 5 days all my forward motion and hard work to be accepted in Main Pop(ulation) in Sydney was destroyed here.

"I was ­assaulted on the 1st. Happy New Year to me. No real damage done. Purple eye, few bruises, all ­because the women didn’t want ‘likes of me’ in their unit."

Her friend told the publication that she fears for her life while imprisoned because she is suffering "physical, emotional and psychological trauma". 

Now, in a handwritten four-page letter to NSW Attorney-General Mark Speakman, obtained by News Corp Australia, Kathleen has begged him to “soften your heart”.

"To them, this isn’t only about helping Kathleen Folbigg," she writes, "but rather about a need for scientific proof to be listened to, respected and heeded. I pay homage to all scientists involved. They have removed the stigma of being perceived as an evil monster, removed the anxiety and fear that I have suffered every day for over 30 odd years.

"Following the petition for a pardon my day-to-day existence has changed. I now receive massive support from so many people."

Article originally published August 2020 and updated in August 2021, November 2022 and May 2023 with new details. 

Feature image: AAP/Joel Carrett/Mick Tsikas.