Will genetic mutations set a mother convicted of killing her four children set her free?

Folbigg's four children died
in a decade.
Caleb died in 1989 when he was just 19 days old
.
Patrick and Sarah are 8 months and 10 months old
, respectively.
Shortly after Laura's death, Kathleen Folbigg came under suspicion and eventually went to trial, and the case became a dramatic public flashpoint
.
At the time, multiple deaths from SIDS in the same family were highly suspected, especially the suspected mother, Kathleen Folbigg
.

The suspicion stems, at least in part, from Roy Meadow
, a British paediatrician who studies child abuse.
In 1997, he made public the idea that "the sudden death of a baby is tragic, two are suspicious, and three are murders, unless there is other evidence
.
" At the trial, this line of thinking apparently influenced the testimony of some experts
.
Emma Cunliffe, a legal scholar at the University of British Columbia in Vancouver, Canada, wrote a book on Kathleen Folbigg's case in 2011 called Murder, Medicine, and Motherhood, mentioning that several leading pathologists testified that they had never encountered multiple SIDS deaths in a single family, meaning that this is nearly impossible — despite the fact that there are such cases
in the literature.

In fact, before the trial began, scientists had already expressed concerns about Roy Meadow's idea, especially its application
in legal cases.
Sally Clark, a mother incarcerated in the UK under similar circumstances, successfully challenged her conviction, in part because Roy Meadow's argument was statistically untenable and made unfounded assumptions
about the incidence of SIDS.
By 2003, the idea had been largely challenged, and Roy Meadow was eventually removed from the UK Medical Register in 2005 for misleading testimony he gave during Sally
Clark's trial.

But Kathleen Folbigg has other circumstantial evidence
against her.
A prosecutor excerpted some of Kathleen's guilt and remorse expressed in her diaries about her inadequacies as a mother, and used the diaries as a confession
.
The prosecution's case relies heavily on testimony from her husband, Craig Folbigg
.
Craig Folbigg, after reading the diary, was convinced that his wife had killed their children
.
The jury agreed
.
Several appeals failed
.

However, Kathleen has always insisted that he is innocent and has not stopped fighting
for freedom.
In August 2018, following a petition by her solicitors, NSW Attorney General Mark Speakman announced that her conviction would be reviewed
based on new evidence on multiple cases of accidental death in the same family.
This will lead to the first investigation
into the conviction.

Influence of genetic factors

As part of the preparations for the investigation, Kathleen's lawyers approached Carola Vinuesa, a geneticist at the then Australian National University (ANU) in Canberra, to sequence and analyse
Kathleen's DNA.
The idea was to see if she carried any mutations that might provide another explanation
for their death if inherited by the children.
Vinnesa agreed to help
.
Her colleague Todor Arsov, a Sydney-based geneticist, went to the nearby Silverwater Women's Correctional Centre, where Kathleen was held, to take samples
from her.
In December, Arsov and Vinnesa were in the kitchen flipping through sequence data, looking for mutations
associated with sudden death.
Within 20 minutes, they both discovered something interesting: a gene variant
called calmodulin 2 (CALM2).

Humans have three calmodulin genes that code for the same proteins that bind to calcium and control calcium concentrations within cells, which help regulate functions
such as heart contractions.
Mutations in these genes are extremely rare, but people with mutations often suffer from severe heart disease and sudden death are reported
.
Vinnuesa thinks the finding warrants further study
.
She suggested Kathleen's lawyer try sequencing the children's and their father's DNA
.

At the beginning of 2019, experts met
.
They included Vinuesa's colleague at the Australian National University, geneticist Matthew Cook, who joined the study remotely, and three genetics experts
from the Sydney state health department.
Jonathan Skinner, a paediatric cardiologist and cardiac electrophysiologist at Starship Children's Hospital in Auckland, New Zealand, also joined the discussion
via video link.

The scientists succeeded in extracting DNA
from the four children.
A hospital in Sydney had frozen fibroblasts from Laura's 1993 autopsy and Caleb's coroner's coroner's court had frozen liver tissue
from Patrick's 1991 autopsy.
A lab in Melbourne sequenced the entire genome from a heel prick sample routinely collected at the birth of a child and extracted protein-coding parts
of the genome from another child's heel prick zaka.
The children's father, Craig Folbigg, declined to provide the DNA
.

By agreement, the experts split into two groups to analyze Kathleen's genome
.
Vinnuesa and Cook from Canberra formed a group
.
Another team of experts in Sydney – genetic pathologist Michael Buckley, clinical geneticist Alison Colley and experts in both fields Edwin Kirk and Skinner – formed another team

To determine whether a variant causes disease, geneticists look at a variety of evidence
.
These factors include: whether a variant is rare or absent in the population, meaning it has been selected to fight; whether the person or family carrying the variant has any clinical manifestations of the disease; and whether studies on cellular or rodent models confirm the effects of this variation on
protein function and health.

Each piece of evidence can be scored
using a five-layer scale created by the American Academy of Medical Genetics and Genomics (ACMG), from benign to pathogenic.
In the middle is "variant of uncertain significance," a confusing classification that neither explicitly nor implies that a particular variant causes the disease
.

Cunliffe said if the investigation found that genetic variants in one or more of the children "may be sick" or "sick," it could create enough reasonable doubt about Kathleen's guilt to overturn her conviction
.

Both teams started with a holistic approach, scanning the genome using bioinformatics tools for rare variants
.
These are not cause for concern in themselves, nor are they signs of disease — most rare variants are harmless — but they are a good place to start
when looking for the cause of an underlying genetic disorder.
The Sydney team found 279 in a sample of 5 people
.
By filtering genes associated with heart disease, respiratory disease, or sudden death, they narrowed the list down to nine, each finding a different combination in the four children and their mothers, containing variants
in CALM2.
Kathleen and her two daughters, Sarah and Laura, share the mutation
.

Vinuesa and Cook of Canberra conducted a similar process
using their own bioinformatics tools.
The findings of the two research groups overlap well: both found the CALM2 variant and the MYH6 gene variant
.
The Canberra team also proposed a third variant: a mutation in IDS, a gene linked to a metabolic disorder of Hunter syndrome that can lead to seizures and death, which one of the boys, Patrick
, had in it.

But when the teams released their report in March 2019, they disagreed
on how the rare variant would be classified.
Although the Canberra team believes that both the CALM2 and IDS variants are "likely to cause disease", the Sydney team concluded that neither was pathogenic
.

In April of this year, the hearing began
.
For three days, lawyers assisting the investigation questioned genetics
and cardiologists.
The two research groups eventually agreed that the variants in IDS and MYH6 were of uncertain significance and unlikely to be responsible
for child deaths.
But the two groups could not agree
on how to classify the variants in CALM2.

Vinnesa and Arsov, who participated in the Canberra research team report, said at the hearing that the classification of "probably pathogenic" was based on several ACMG criteria: the variant appeared to be entirely new because it did not exist in the population database at the time (CALM3 later appeared in one database).

Computer simulations predict that it will disrupt the function
of the protein it encodes.
The team also believes that there is a plausible pathway to explain how this variation triggers sudden death
.

But members of the Sydney research team questioned the classification, in part because Kathleen was apparently healthy
despite the variant.
Vinnuesa believes Kathleen's health is not entirely clear
.
She also explained that some people who carry disease-causing variants often do not show obvious signs or symptoms
.

Cardiologist Skinner agrees that this is the case
with some inherited heart conditions.
He agrees that mutations in the calmodulin gene do produce life-threatening arrhythmias — irregular heart rhythms
.
But he said in the investigation that arrhythmias "don't appear to show up in babies who sleep quietly.
"
In addition, he added, in the literature, "there is not a single case of sudden death under the age of two"
.