A detective has revealed exactly how police caught Jill Meagher's killer.

How detectives pieced together a case with almost no clues to find a killer.

Detectives had only a few clues to Jill Meagher‘s disappearance on September 22, 2012: an abandoned bag, an unanswered phone call and a missing person’s report.

The bag was picked up off Hope St in Melbourne by a local on the night she was killed. It was later returned to where it was found – presumably because the thief was afraid of being implicated in the murder – and discovered by police.

Meagher had been on the phone to her brother in early hours of September 22, but did not answer minutes later when he tried to call her back.

Police had no other evidence about what might have happened to the bright 29-year-old.

Meagher’s case quickly became a priority for the missing persons unit. Although she had been gone little over 24 hours, Meagher’s case was flagged as unusual because she had never gone missing before.

In his first interview since the arrest of Adrian Bayley, head detective Senior Sergeant Dave Butler says he had a bad feeling about the Meagher case immediately.

“There was just something about it,’’ Butler said. “With missing persons, you develop a sense for it. Something was just not right. Who she was, the overall circumstances, there was no history of going missing.’’

Butler and his team had little more than a sense to go on, however, with Butler describing their position at the beginning of the investigation as “working blind”.

Only days into the investigation, other detectives were starting to lose hope at ever piecing together such sparse evidence, but Butler refused to lose hope.

“If we do the little things well, somewhere along the way we will discover something,” he said.

Still, he admits he believed it would be months, not days or weeks, before his team made an arrest.

On the night on Monday, September 24, the focus of the investigation shifted from a missing person to a homicide. There had been no sign of Jill for 48 hours, and police had found nothing to indicate she was still alive.

“That was the moment it crystallised for me: this is what I think it is,’’ Butler said.

“It was important to focus and then eliminate those closest to Jill as a priority.’’

As with many murder investigations, Butler and his team investigated Jill’s close family and friends first, seeking to eliminate the most likely suspects before proceeding with a wider investigation.

Only a day after these interviews began, and her husband Tom Meagher had been eliminated as a suspect, Butler caught a break that would change the nature of the entire investigation.

Tasked with checking the vehicle registrations of every car that had driven through the CityLink tollway on the night of Meagher’s disappearance, where her phone had been tracked on the night, two homicide detectives noticed an anomaly: an Asta hatchback registered to the bailed serial rapist Adrian Bayley had driven through the tollway on the night of September 22.

Bayley’s criminal records was checked and his licence brought up, allowing police to compare his photograph with the chilling CCTV footage on Meagher talking to a man in a blue hoodie outside the Duchess Boutique dress shop on Sydney Rd.

When police traced Meagher and Bayley’s phones to a location side-by-side, they knew Bayley was their man.

The evidence that would get Bayley arrested and eventually convicted was a simcard found in his home that had been removed from Meagher’s phone and snapped.

When asked why he might have such an item in his possession, Bayley could only reply, “I don’t want to explain that.”

Senior Sergeant Butler has been nominated for a Pride of Australia award for his work in solving Meagher’s murder and bringing her killer to justice.

Read more: 

Adrian Bayley’s former housemate tells the “story that could have saved Jill Meagher.”

Priest says Jill Meagher “should have been home in bed” the night she was murdered.

We can finally reveal the details of Jill Meagher’s killer’s violent past.