Ex-FBI supremo Clarence Kelley knew that one of the secrets of good decision-making is to admit what you don’t know. What can we learn from him? Access our full decision science guide for police leaders here.

In 1961, a man named Clarence Kelley retired from the FBI and took up the job of leading the Kansas City Police Department. He joined the department at a tricky time. Crime had started to tick upwards across the United States, and as the decade progressed, Kansas and other police forces had to respond accordingly: with more police and more patrols, particular vehicle patrols.
In 1972, however, once he had firmly established his reputation and relationships in the city of his birth, Kelley went out on a limb and made a confession. As he put it, “Many of us in the department had the feeling we were training, equipping, and deploying men to do a job neither we, nor anyone else, knew very much about”. Working with the independent research body the Police Foundation, Kelley decided to do something about this. He embarked on one of the boldest experiments in criminal justice history. Over the course of a year, researchers tracked what happened when he entirely eliminated vehicle patrols from 5 districts, doubled them in five other districts, and left them the same in the remaining five areas.
Researchers were tasked with closely tracking what was happening to crime – and they introduced surveys of residents to augment the data recorded by the police. This data was intended to allow Kelley to reintroduce patrols if neglected areas collapsed into chaos. But, for two reasons, he never had to. First, Kelley had been poached to be the new FBI Director after J. Edgar Hoover’s precipitous fall from grace in the wake of the Watergate scandal. Kelley was replaced by Joseph McNamara, who agreed to carry on the experiment. Second, crime did not soar. In fact, the results were startling in their lack of drama. In the areas with double patrols, the areas with no patrols and those with stable patrols, crime trends were broadly the same. Vehicle patrols were not making the difference to crime rates most had hoped.
The easy conclusion to draw was that the police weren’t making a difference to crime. But in fact they do – as the wider experiments I share in my book Criminal reveal. What the experiment instead showed was that this particular mode of police activity – random vehicle patrols – was grossly ineffective. The results of the experiment therefore helped to encourage police departments in the US and internationally to gradually start following their own mantra: ‘Sir, madam. Get out of the vehicle’. And though it took several decades, the trial encouraged police to become more embedded in communities and more focused on targeted patrolling of specific crime hotspots.
The style of leadership exhibited by Kelley and McNamara is one that is open about the limits of our knowledge about ‘what works’; willing to experiment and take risks; eager to collaborate with those outside policing; and not in thrall to conventional wisdom. And their approach, championed by George Kelling of the Police Foundation and by several other police leaders and academics has slowly but surely led to the development of the evidence-based policing movement, and the continual evolution of police practice across the world.
Creating experiments in policing – both to test what reduces crime, what works in improving victim and witness satisfaction for crime, and even in management approaches is challenging. But these issues are relatively easily overcome with the right support and expertise. Indeed, it is now possible to harness real time data to create an experimental ecosystem that is continually testing what works and informing decisions. The truth is that the hardest part of what Kelley did is to admit ignorance and to question whether what he was already doing was working.
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This is a version of an article produced for Police Oracle.
The full story on where and how police activities affect crime rates is found in chapter eight of CRIMINAL: THE TRUTH ABOUT WHY PEOPLE DO BAD THINGS, available here.