How a 22-year-old female cop nailed Australia's most dangerous serial killer couple.

It was Nomember 10, 1986. Constable Laura Hancock was just 22 years old and the only female police officer on duty at Palmyra Police Station.

She had never taken a statement before.

On that day, Kate Moir entered the station.

We know now that Moir had been abducted at knife point by David and Catherine Birnie. They had murdered four women in their home in the 1980s and Moir was to be their fifth victim. She was kept prisoner in their home for one night and raped before escaping through a window when David was at work and Catherine distracted.

Hancock was charged with the job of interviewing her.

As a 22-year-old novice, Hancock was firm in her belief that the only reason she was given the interview because her superiors did not believe Moir's story.

“I was told that it was a bizarre story and to stitch her up for a false report. And I’ll never forget those words, that is verbatim, I have lived those words for 30 years,” she told Channel Seven’s Murder Uncovered.

They are words that clearly linger on Hancock's conscience, but ones she equally ignored.

Hancock walked in and out of the interview in an attempt to convince her superiors that she had an unwavering belief in Moir's story. At the time, Moir thought she kept leaving the interview room to cry. It was a heavy story, and Hancock was only a few years older than 17-year-old Moir.

But it was Moir's dead-pan conviction in David and Catherine Birnie's evil that had Hancock convinced.

“It became apparent fairly quickly that Kate was in some sort of form of shock,” she said.

“She believed that there had been others, and that they had died, and she was going to die and she was very emphatic with that.”

Moir's priority, at the time, lay in the pursuit of her captors.

"She was calm, tired, very, very blank, very factual, matter of fact ... little emotion at that point,” Hancock said.

“The focus was ‘This is who they are, go get them’ not ‘oh my God this is what I’ve just been through, the poor me’. It was ‘listen to me, here’s my story, this is why, this is how and this is who, go get them’."

And so they did. Moir's captors had given her false names, but she spotted a medicine bottle with a name on it and committed it to memory. Hancock took that name to her superiors, and the case suddenly grew serious, with police recognising the name and pursing the couple immediately.

Hancock was 22, taking her first statement and whose persistence had just nailed two of our most dangerous serial killers.