THE New York Police Department got an earful from Shira Scheindlin, a federal judge, on the morning of August 12th. In the case of Floyd v City of New York, America’s largest police force was chastised for its “stop and frisk” policy whereby, over the past nine years, 4.4m people were spontaneously stopped and searched on the suspicion "that criminal activity ‘may be afoot’". The federal district court in Manhattan issued a stunningly broad ruling, finding that the NYPD has failed to uphold New Yorkers’ fourth-amendment right against unreasonable searches and, through “indirect” racial profiling of blacks and Hispanics, violated the 14th-amendment guarantee of equal protection. Judge Scheindlin’s decision does not end stop and frisk but calls for broad reforms in the way it is carried out. Among other changes, police training and supervision will be revised and officers will be asked to wear small “body cameras” to record street encounters and increase accountability. An independent monitor, Peter Zimroth, a former prosecutor and defence attorney, will oversee the reforms.

Michael Bloomberg, the city’s outgoing mayor and staunchest defender of the policy, promised to appeal the ruling. "Throughout the trial that just concluded, the judge made it clear she was not at all interested in the crime reductions here or how we achieved them," said Mr Bloomberg. "In fact, nowhere in her 195-page decision does she mention the historic cuts in crime or the number of lives that have been saved."

Putting a finer point on it, Mr Bloomberg called the ruling a “very dangerous decision”. And, as usual, he cited the recent decline in crime to pound home his point. "Think about what that change really means: if murder rates over the last 11 years had been the same as the previous 11 years, more than 7,300 people who today are alive would be dead."

But his reasoning goes awry in two ways. First, there is little evidence that stop and frisk has accomplished all that Mr Bloomberg claims it has. Robert Gangi explained one facet of the mayor’s weak empirical case a year ago in the New York Times:

The misguided emphasis on numbers explains the exponential increase in stop and frisks during Mayor Michael Bloomberg's tenure, a leap of 600 percent, from 97,296 in 2003 to 685,724 last year. Echoing the dubious claims of his police commissioner, Raymond Kelly, Bloomberg defends tactics like stop and frisk by citing crime reduction in the city. But the relevant data hardly serve his argument. The drop in murders in New York City, for example, from 2002 until now has been about 12 percent, from 587 annually to 536. During the same period, the number of murders declined by 43 percent in Washington and by 50 percent in Los Angeles, two cities that have less aggressive stop and frisk tactics.

This comparative context is important, as is the familiar but frequently ignored distinction between correlation and causation: crime in New York City has indeed fallen since stop and frisk was instituted in 2004, but this alone does not establish a causal relationship between the latter and the former. According to the Floyd ruling, guns have been recovered in only 1.5% of stops in which suspects were frisked. The policy has led to many more people being busted for marijuana possession.

But even if we accept all of Mr Bloomberg’s empirical claims regarding the crime-reducing effect of stop and frisk, there is the matter of what forms of policing are consistent with the constitution. As Judge Scheindlin wrote,

[T]his case is not about the effectiveness of stop and frisk in deterring or combating crime. This Court’s mandate is solely to judge the constitutionality of police behavior, not its effectiveness as a law enforcement tool. Many police practices may be useful for fighting crime—preventive detention or coerced confessions, for example—but because they are unconstitutional they cannot be used, no matter how effective.

Here is the point that Mr Bloomberg consistently ignores. I have no doubt of his and Mr Kelly’s sincere motivation to protect New Yorkers from violent crime. I don’t think either man is motivated by racial animus toward black and Hispanic men, the targets of 83% of the 4.4m stops. But both officials come across as callously narrow-minded when confronted with evidence of the toxic effect the policy has had on community relations. They view the stops as basically harmless inconveniences that make everybody safer. In fact, stop and frisk represents a municipal watch programme for minority youth that violates constitutional rights, breeds discontent and suspicion of law enforcement officials and exacerbates racial tensions in the city.

(Photo credit: AFP)