By Brittany Shammas
The children all died before their 2nd birthdays: Caleb at 19 days, Patrick at eight months, Sarah at 10 months and Laura at a year and a half.
Over a decade, Kathleen Folbigg gave birth to each baby and then mourned the baby's death, one after another, saying that she had found them lifeless in their cribs.
Then, in 2003, a jury convicted the Australian woman of smothering them. She was sentenced to 40 years in prison for murder and manslaughter, branded by the media as the country's "worst female serial killer" and "most hated woman."
But 18 years into Folbigg's sentence, and more than 20 years after the death of her last child, a growing list of scientists say they believe she is innocent - the victim of an "ongoing miscarriage of justice."
In a petition requesting the 53-year-old be pardoned and released, 90 scientists say the four children died of natural causes. They argue that genetics, not murder or manslaughter, may explain the deaths that haunted the Folbigg family.
"Ms. Folbigg has suffered and continues to suffer emotional and psychological trauma and physical abuse in custody," says the petition, sent to the governor of New South Wales in March. "She has endured the death of her four children and has been wrongfully incarcerated because the justice system has failed her."
Among the signatories are two Nobel laureates, along with the president of the Australian Academy of Science. They hail from Australia and eight other countries. Four are from the United States.
The courts have upheld Folbigg's conviction even as advances in science raise new questions about the case. Weeks after the petition was sent, a three-judge panel tossed out her appeal of a 2019 inquiry that affirmed the jury's verdict.
But Folbigg has always insisted she didn't harm her children. Her trial was based largely on circumstantial evidence and the argument that four deaths within the same family could not have happened by coincidence. Central to the case were closely scrutinized diary entries, including one in which Folbigg wrote that Sarah "left. With a bit of help."
In phone calls recorded for the documentary series Australian Story, Folbigg said the entries were "written from a point of me always blaming myself."
WATCH: Scientists say there's compelling evidence Kathleen Folbigg didn't murder her four children
"I blamed myself for everything," she said. "It's just I took so much of the responsibility, because that's, as mothers, what you do."
Folbigg described her life as made up of a series of "never-ending battles and things that I have to get over and conquer." When she was 18 months old, her father stabbed her mother to death after an argument - a detail that would one day feature prominently in coverage of her murder case. He spent 15 years in prison, according to details in the 2019 inquiry, and Folbigg lived with relatives before being put in foster care.
She met the man who would become her husband, Craig Folbigg, on a dance floor when she was 15. She viewed him as her "knight in shining armour," according to an account included in the 2019 inquiry. They married in 1987, and in 1989, she gave birth to their first child, Caleb.
The baby died weeks later. His death was attributed to sudden infant death syndrome, or SIDS.
It was the start of a tragic pattern. Three more times in the next 10 years, Folbigg would scream to her husband that something was wrong with their baby. She kept wanting to have more children, one of her diary entries suggested, because she hoped to prove herself.
"What sort of a mother am I, have I been? A terrible one," said the 1997 entry. "That is what it boils down to. That is how I feel and that is what I think I'm trying to conquer with this baby: to prove that there is nothing wrong with me. If other women can do it, so can I."
Patrick died Feb. 13, 1991, his death certificate noting he was blind and choked due to epileptic fits. Sarah died Aug. 30, 1993, with SIDS listed as the cause. Laura died March 1, 1999. That time, a doctor recorded the cause of death as "undetermined," citing the deaths of her siblings.
Craig Folbigg would later say that he "had the odd suspicion" but couldn't get his head around it until May 1999, when he came across a diary of his wife's and started reading. What he saw made him feel sick, he said, and he soon went to police.
In passages that featured heavily in the case, Kathleen Folbigg wrote that Laura was "a fairly good-natured baby," adding, "Thank goodness. It has saved her from the fate of her siblings. I think she was warned." She also wrote, "I am my father's daughter."
Prosecutors pointed to her words while arguing it was virtually impossible that one family could have four children die of natural causes.
"I can't disprove that one day some piglets might be born with wings and that they might fly. Is that some reasonable doubt? No," the prosecutor said during the 2003 trial. "There has never ever been before in the history of medicine that our experts have been able to find any case like this. It is preposterous."
But the scientists behind the petition for Folbigg's release say there is no evidence to support the smothering allegations. They noted that the premise that one family is unlikely to experience multiple deaths is based on a theory, Meadow's Law, that has since been discredited.
Two United Kingdom convictions based on the maxim, which claims two infant deaths are suspicious and three are murder unless proven otherwise, have been overturned.
In the years since Folbigg began her sentence at Cessnock Correctional Centre, significant advances have been made in genetics, raising new doubts. The petition to free her says there is now "significant positive evidence" the four died of natural causes.
In 2018, after Folbigg's attorneys asked geneticists to look at the case, scientists sequenced her genome and the genomes of her children. They discovered that she and her daughters had a rare mutation in a gene called CALM2. The mutation can cause sudden death in infancy and childhood, the petition says. In a 2020 study, a team of researchers concluded that the variant changed Sarah's and Laura's heart rhythms and was a "reasonable explanation" for their deaths.
Further investigation found that Caleb and Patrick carried a different rare genetic variant that, in studies with mice, has been connected to epileptic deaths at a young age, the Associated Press reported.
Jozef Gecz, a paediatric geneticist who signed the pardon petition, acknowledged to the news wire that there was stronger evidence of natural death in the girls' cases. He said scientists are still studying potential genetic causes for the boys' deaths.
"We know now from a lot of our work with families who are unfortunate in that they carry genetic risk that it does happen," he said.
The petition for Folbigg's release argues that the courts have ignored medical evidence in favour of interpretations of a mother's vague journal entries. It says a reasonable person should have doubts about whether she killed her children, adding that "deciding otherwise rejects medical science and the law that sets the standard of proof."
Folbigg, whose sentence was reduced to 25 years on appeal, is not set to be released until 2028. During the 2019 inquiry, the AP reported, a prosecutor told her the diary entry mentioning "a bit of help" approached an admission to killing her child.
"I say it's me admitting how badly responsible I felt," Folbigg responded, "and I will always feel that way."