simple. It was based on a quirk in the American legal system.
The Fourth Amendment to the U.S. Constitution protects citizens from “unreasonable searches and seizures.” That’s why the police cannot search your home without a warrant. On the street, similarly, a police officer must have a good reason—“reasonable suspicion”—to frisk you.2 But if you’re in your car, that standard is not at all hard for a police officer to meet. Traffic codes in the U.S. (and in fact in most countries) give police officers literally hundreds of reasons to stop a motorist.
“There are moving violations: speeding, running a red light. There are equipment violations: a light that doesn’t work, a tire not quite right,” legal scholar David Harris writes.
And then there are catch-all provisions: rules that allow police to stop drivers for conduct that complies with all the rules on the books, but that officers consider “imprudent” or “unreasonable” under the circumstances, or that describe the offense in language so broad as to make a violation virtually coextensive with the officer’s unreviewable personal judgment.
There was even a Supreme Court case in which a police officer in North Carolina stopped what he thought was a suspicious driver, using the pretext that one of the car’s brake lights was out. As it turns out, it’s perfectly permissible in North Carolina to drive with one brake light out, so long as the other one works. So what happened after the driver of the car sued, claiming he had been stopped illegally? The Supreme Court ruled in favor of the officer. It was enough that he thought driving with only one brake light seemed like an infraction. In other words, police officers in the United States not only have at their disposal a virtually limitless list of legal reasons to stop a motorist; they are also free to add any other reasons they might dream up, as long as they seem reasonable. And once they’ve stopped a motorist, police officers are allowed, under the law, to search the car, so long as they have reason to believe the motorist might be armed or dangerous.
Kansas City decided to take advantage of this latitude. Sherman’s proposal was for the police department to detail four officers, in two squad cars. Their beat would be District 144. They were told not to stray outside the area’s 0.64 square miles. They were freed from all other law-enforcement obligations. They didn’t have to answer radio calls or rush to accident scenes. Their instructions were clear: watch out for what you think are suspicious-looking drivers. Use whatever pretext you can find in the traffic code to pull them over. If you’re still suspicious, search the car and confiscate any weapon you find. The officers worked every night from 7 p.m. to 1 a.m., seven days a week, for 200 consecutive days. And what happened? Outside District 144, where police business was conducted as usual, crime remained as bad as ever. But inside 144? All of the new focused police work cut gun crimes—shootings, murders, woundings—in half.
Remember, the police had all but given up by that point. Hotline? Nobody calls it. Concealed-weapons detection? A crew from 20/20 comes down and twice goes home empty-handed. Lee Brown, up in New York City, was mourning the powerlessness of the police to do anything serious about violent crime. Everyone remembered the previous Kansas City experiment, which had plunged the law-enforcement community into twenty years of despair. But now the same city had come back, and this time they were declaring victory. “I don’t know why it didn’t occur to us to really focus on guns,” the Kansas City police chief said after the results came in. He was as stunned as everyone else at what just two extra patrol cars had accomplished. “We usually focus on getting the bad guys after a crime. Maybe going after guns was too simplistic for us.”
The first Kansas City experiment said that preventive patrol was useless, that having more police cars driving around made no difference. The second Kansas City experiment amended that position. Actually, extra patrol cars did make a difference—so long as officers took the initiative and stopped anyone they thought suspicious, got out of their cars as much as possible, and went out of their way to look for weapons. Patrol worked if the officers were busy. The statistics from the final report on the experiment were eye-opening. Over the seven months, each patrol car issued an average of 5.45 traffic citations per shift. They averaged