A SIMPLE yet successful trial of police officers patrolling trouble hotspots for just 13 minutes once a day has slashed crime rates.

The experiment analysed nearly six million GPS pings from dozens of mobile phones handed out to participating officers which recorded their location every two seconds.

On random “treatment days” between August and March, cops were asked to patrol 15 different areas in Armadale for around 13 minutes, ranging from CBD hotspots, train stations and fast food outlets.

Then on “control days” there would be no patrolling so analysts could see what happened.

The extrapolated results of the eight-month trial, conducted by the WA Police Force’s evidence-based policing (EBP) unit, showed there would be 224 fewer offences committed a year, a drop of 22 per cent.

A new index used in this trial, called “crime harm”, which measures the amount of prison time an offence committed by a first-time offender would earn, shows a 62 per cent reduction over a year, with 35 fewer years of crime harm.

WA Police Force director of criminology and former University of Cambridge lecturer Geoffrey Barnes said: “That’s all we did — one visit a day for 13 minutes prevents 224 offences ... and not only are we preventing offences but we’re preventing more serious offences from taking place just by going once for 13 minutes.

“There was a joke (about EBP) ... that we became known as Evidence-Based Parking in Armadale. But wow, what a powerful effect and we know that it wasn’t anything else that caused it but this patrolling.

“There can be no argument after this of saying that police in WA have a huge impact just by standing there.”

Mr Barnes said this project had also discovered a “residual deterrence” — that one daily visit resulted in four days of less crime.

“Only on the fifth day does crime start to creep back up,” he said. “What it tells us is we went 13 minutes one time four days ago and it’s still having an effect ... so don’t let them go cold for more than four days in a row. Nobody else in the world has found this. We are the first ones to look for this.”

Mr Barnes said as the force moved into the digital age there would be nothing stopping officers from filing reports from the road, rather than returning to their stations.

“Why not park up at a hotspot ... spend those 15 minutes typing up your report, but being highly visible,” he said.

The results of this trial have been presented to Police Commissioner Chris Dawson. The EBP team has up to 10 projects on the go, looking for innovative, scientifically-tested crime solutions.