Kansas City Preventive Patrol Experiment: Is It Working?

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This article is an excerpt from the Shortform summary of "Talking to Strangers" by Malcolm Gladwell. Shortform has the world's best summaries of books you should be reading.

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What was the Kansas City preventive patrol experiment? Why was it so groundbreaking? Why have we failed to replicate it successfully across the country?

We’ll cover what the Kansas City experiment was, how it used the theory of coupled behaviors, or coupling theory, and why it was so successful. Then, we’ll look at why it hasn’t been particularly successful in other parts of the country.

The Kansas City Experiment + Coupled Behaviors

A person’s likelihood to commit a crime is coupled with their context—like their personal history, their geographic location, or their access to guns. The Kansas City Police Department completed an experiment that proved this theory. This was the Kansas City preventive patrol experiment, or simply the Kansas City experiment.

In the early 1990’s, the Kansas City Police Department decided to study how to deploy extra police officers in an effort to reduce crime in the city. They hired criminologist Lawrence Sherman and gave him free rein to make changes in the department and head the Kansas City patrol experiment. 

Sherman was sure that the high number of guns in Kansas City was a direct cause of the city’s high level of violence and crime. So he decided to focus his experiment specifically on guns in the 144th patrol district of Kansas City, one of the most dangerous areas in the city. Sherman’s experiment was a relatively simple one that made use of a loophole in the American legal system. 

The loophole: The U.S. Constitution requires police officers to have a reasonable suspicion in order to search a citizen, which is a relatively difficult standard to meet when the citizen is at home or walking down the street. However, when the citizen is driving a car, the standards for reasonable suspicion are much lower. Police can stop a driver for hundreds of legal reasons, such as running a red light or driving with a brake light that’s out. And once they have stopped a driver, police are allowed by law to search the car for any reason they believe might be suspicious. 

Strategy of the Kansas City Preventive Patrol Experiment

Sherman chose to take advantage of this loophole by deploying four officers in two cars to patrol District 144 at night. He told these four officers to watch out for any suspicious-looking drivers and pull them over for any reason they could justify by law. Sherman told the officers to search as many cars that fit the specific requirements and confiscate as many guns as possible. These officers were effectively searching for a needle in a haystack. The ultimate goal was to find a gun or drugs. 

Sherman was careful to warn police leaders about the dangers of aggressive preventative patrol. He knew that overly suspicious (and therefore aggressive) police officers could create distrust between the police and the public. That’s why the four officers in Sherman’s experiment went through specialized training and only worked in District 144 at night—Sherman wanted to make sure that they knew how to target the right kind of traffic stops, in the right kind of locations, at the right times, that led to the right kind of searches.

Results of the Kansas City Preventive Patrol Experiment

The four officers deployed by Sherman worked from 7 p.m. to 1 a.m. every night for 200 consecutive nights in District 144. During that time, Sherman’s officers issued 1,090 traffic citations, stopped 948 vehicles, arrested 616 people, and seized 29 guns. They averaged one stop every 40 minutes. And the result of the Kansas City preventive patrol experiment? Gun crime was cut in half in District 144 over those 200 days. 

Sherman was able to prevent violent crime with only four officers, simply by keeping the officers extremely busy searching for guns. The experiment was successful because it made crime-fighting strategies more focused—it targeted one aspect of the coupled behavior (guns) in order to prevent the other coupled behavior (crime). 

Reaction to the Kansas City Experiment

Sherman’s success in District 144 with the Kansas City preventive patrol experiment inspired law enforcement officials. Police departments across the country asked Sherman how they could achieve the same results, and Sherman shared the technique with them. 

In the years following the second experiment in Kansas City, police departments across the nation began to follow Sherman’s model of the Kansas City patrol experiment. For example: 

  • North Carolina Highway Patrol doubled the number of traffic stops made per year from 400,000 to 800,000 over the course of seven years. 
  • The American Drug Enforcement Agency began to teach courses on how to use traffic stops to catch drug mules. 
  • Immigration officials used traffic stops to apprehend illegal immigrants. 

Police officers in America today stop around 20 million drivers per year (approximately 55,000 stops per day), all in an effort to replicate Sherman’s success in Kansas City. However, one of the most crucial elements of Sherman’s technique has been lost—the focus on coupled behaviors. For example, when North Carolina Highway Patrol doubled their stops made per year, they did not focus on suspicious-looking drivers likely to commit crime in a particular area at a particular time—they just stopped as many drivers as they could.  

Police Training Post-Kansas City Experiment

After Sherman’s success in the Kansas City preventive patrol experiment, police training began to change. The new brand of police officer is supposed to be highly suspicious—always on the lookout for any small behavior that could indicate criminal intent. In other words, police officers are being trained to not default to truth. 

Police officers are taught that savvy criminals would be careful not to make any obvious infractions. So they learn how to use creative tactics to catch criminals in the act. Here are some examples:

  • Look for air fresheners in the car—they could indicate that the driver is trying to hide the smell of drugs. 
  • Park your squad car in a suspicious location and wait for drivers to make an illegal stop when they see the car. 
  • Look for fast food in the car—this could indicate that the driver is unwilling to leave the car for long periods of time because of expensive cargo, like drugs. 
  • When going through a routine traffic stop, draw out the interaction for as long as possible. Ask a lot of questions and watch to see if the driver slips up and gives inconsistent answers. 

It’s important to note that most drivers who have air fresheners or who stutter when talking aren’t criminals. But post-Kansas City preventive patrol experiment, police were told that in order to be successful, they had to operate as though every civilian they came across was a suspect. They had to break their default to truth. 

Police post-Kansas City are also trained to strongly assume transparency—to operate under the assumption that guilty-seeming behavior was an accurate indication of guilt. For example, the Reid Technique, which is used in police training in two-thirds of all American states, instructs police officers to use eye contact to gauge a person’s innocence. If the person breaks eye contact, the Reid Technique says that they are probably guilty. 

The law enforcement community at large missed the real lesson of Sherman’s success—that preventative patrol only works if it is focused on behaviors or places that are specifically coupled with crime. That is an understandable human error on the part of law enforcement officials. For some reason, the idea of coupled behaviors is difficult for most people to grasp.  When you combine that with broken default to truth and absolute assumption of transparency (like post-Kansas City police are trained), you get tragic interactions—like Sandra Bland and Brian Encinia.

Kansas City Preventive Patrol Experiment: Is It Working?

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Amanda Penn

Amanda Penn is a writer and reading specialist. She’s published dozens of articles and book reviews spanning a wide range of topics, including health, relationships, psychology, science, and much more. Amanda was a Fulbright Scholar and has taught in schools in the US and South Africa. Amanda received her Master's Degree in Education from the University of Pennsylvania.

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