The lab detective: how genetic breakthrough freed a mother jailed for killing her children

Kathleen Folbigg spent 20 years in prison until Carola Vinuesa uncovered the truth in a drop of blood. By Rachel Sylvester

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Kathleen Folbigg has suffered unimaginable tragedy in her life. Over the course of a decade she lost not just one, but four of her infant children. They all died, suddenly, in their sleep.

Her first child, a boy called Caleb, stopped breathing when he was just 19 days old. The second, Patrick, was pronounced dead at eight months, and the third, Sarah, was found blue and motionless when she was 10 months old. The fourth child, a daughter called Laura, fell asleep for a morning nap at 18 months old and did not wake up.

There is a heartbreaking recording of the frantic call Folbigg made to the emergency services after Laura died. She tells the operator: "My baby's not breathing ... I've had three go already."

Then Folbigg was accused of killing her babies. She remembers the moment a police officer knocked on the door of her home in eastern Australia. "As soon as I saw him, my face dropped - and then I thought 'you're not serious,'" she says. Her confusion soon turned to terror.

In 2001, she was charged with murder. "I was grieving, and in shock," she says. "I wasn't really concentrating on what the police were doing. It was a case of waking up and deciding whether you were going to survive that day or not." She assumed the truth would prevail and she would be found innocent. "I was believing wholeheartedly that the system was going to do the right thing. It was a great naivety, which I no longer have."