Warning: This post deals with the deaths of four young children.

Kathleen Folbigg is considered to be Australia’s worst female serial killer.

In 2005, the New South Wales based mother was jailed for the murders and manslaughter of her four infant children, which took place between 1989 and 1999.

Her four children – Caleb, Patrick, Sarah and Laura – were aged between just 19 days and 19 months when they passed away at home.

For several years, it was believed the Folbigg children had died as a result of natural causes, including sudden infant death syndrome (SIDS). But after Kathleen’s then-estranged husband Craig found her personal diary, she was arrested.

Watch a clip from Kathleen Folbigg on Australian Story below. Post continues after video…

The words in those diaries, and another uncovered by police, painted a damning picture of Kathleen’s guilt, and led to her 2003 conviction and sentencing to 40 years jail, 30 years non-parole, which was later reduced to 25 years on appeal.

Now, over a decade on from her conviction, Kathleen Folbigg will step into court and give her explanation of what her diary entries about her four deceased infant children meant.

On Monday, Kathleen, who maintains her innocence, will face questioning at Lidcombe Coroner’s Court over her diary entries, her possession of the diaries and her disposal of the diaries.

Kathleen Folbigg’s diary entries.

In an episode of Australian Story last year, Kathleen explained the damning entries within her diaries for the first time.

In one diary entry, Kathleen wrote of her daughter Laura, “She’s a fairly good-natured baby. Thank goodness. It has saved her from the fate of her siblings. I think she was warned”.

In another entry: “I feel like the worst mother on this Earth. Scared she’ll leave me now like Sarah did. I knew I was short-tempered and cruel sometimes to her, and she left. With a bit of help”.

And in another entry while pregnant with her daughter Laura: “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…”

Within the diaries, Kathleen also referenced her father, who killed her biological mother in 1969. “I am my father’s daughter,” she wrote.

Speaking to Australian Story, Kathleen explained that her diaries were written “from a point of me always blaming myself”.

"I blamed myself for everything. It's just I took so much of the responsibility, because that's, as mothers, what you do."

The prisoner also explained that the quote: "She left. With a bit of help" referenced "God or some higher power".

She also spoke about her state of mind when her fourth child, Laura, was born.

"I was so stressed, and so scared, and so feeling vulnerable and so not understanding and so not just dealing or coping with the whole concept that we might be doing this again, so I started writing in those diaries," she said.

"There was a desperation throughout these diaries, if anyone bothered to read the actual whole diaries. They're full of nothing but pain, angst, torture; trying to figure out things, understand the un-understandable," she added.

"Thinking, I've lost these three, why have I lost these three? Laura has to stay, and I was so desperate to grasp at anything, so there were a few comments in there that probably didn't make any sense whatsoever."

In the episode, Nicholas Cowdery, the former NSW Director of Public Prosecutions said that Kathleen's diaries do not amount to confessions of killing any of her four children.

"The diaries are not confessions. They're not admissions of physically harming any children. They are more expressions of her state of mind about certain issues," he said.

What's next in Kathleen Folbigg's case?

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

The inquiry is expected to focus on the evidence or lack of evidence related to whether three or more deaths can occur in a family with no explanation.

The inquiry is expected to take six to 12 months.

If the inquiry finds there is a reasonable doubt as to Kathleen’s guilt, the matter may be referred to the Court of Criminal Appeal for further consideration.

Kathleen is eligible for parole in April 2028.

For more on this topic:

• Kathleen Folbigg, convicted of killing her four children, gives an explosive explanation.
• Kathleen Folbigg is seen as Australia's worst female serial killer. Now she might be getting a second chance.