Introducing...The Lab Detective

The Observer.

It is something that will be with me for the rest of my life.

You know, I've always said I wouldn't want my worst enemies to ever go through this sort of stuff.

Kathleen Folbig is a grieving mother at home in Australia when a police detective turns up at her door.

As soon as I saw her, my face just dropped.

You've got to be you're not serious here.

He's there to arrest her, because over a 10-year period, all four of her infant children have died out of the blue.

At first, it looked like a tragic series of cot deaths, the sudden unexplained deaths of otherwise healthy children.

But when her fourth child died, a daughter called Laura, sympathy turned to suspicion.

Australia's worst female serial killer, Kathleen Folbig.

She was seen as this horrific monster who murdered her children.

She was the most hated woman in Australia.

For the past two decades, she's been where most people believe she belongs, behind bars.

But not everyone believed she belonged there.

I've always said with this case, the devil's in the detail.

Kathleen's best friend Tracy was convinced this was a terrible miscarriage of justice and then lawyers, pediatricians and psychologists started to agree.

They'd seen this happen before.

The case against her relied on circumstantial evidence and something didn't feel right.

A world of several billion people, you can have really, really rare events happen.

But they needed definitive proof.

Do you almost think of yourself as a detective rather than a doctor?

It's a good question.

Yeah, sometimes I think I would have liked to be a detective.

Until finally, a different kind of detective enters Kathleen's life.

A scientist called Carola Vinuesa.

She's a geneticist who specializes in finding clues hidden away in the genes that all humans carry.

Nobody wants to have on their watch a miscarriage of justice, right?

And then, you know, I just remember calling Carola then and saying, well, it looks as if there may be something.

And she makes an extraordinary discovery that changes Kathleen's life.

To be told, we have actually found something.

That was a big Eureka moment.

But the thing is, Kathleen's story isn't the first of its kind

or the last.

And what Carola was telling me was that there's another case that needs to be investigated.

Another mother convicted of murder just last year.

when science could provide an answer.

You know, scientists want to know the truth and want to get to the bottom of things.

And particularly, you know, in a case like this where you feel there's been a miscarriage of justice, right?

And that science can solve it.

So I just couldn't stop.

I'm Rachel Sylvester.

I'm from Tortoise Investigates.

This is the Lab Detective.

A story about how science can shape and reshape the law and the mothers and scientists in search of the truth.

The Lab Detective launches on Tuesday, the 22nd of July.

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The Observer.