The stop-and-frisk tactic is as old as policing itself. But it has been a central law enforcement tool in New York since the 1990’s, when the police adopted the “broken windows” approach, clamping down on minor crime and emphasizing preventive measures against lawbreaking.

New York has experienced a dramatic reduction in crime. But as Judge Scheindlin pointed out, there is no conclusive proof that widespread use of stop-and-frisk itself drove down crime. Crime fell in many cities, including those that did not adopt the approach.

There is no dispute that minorities are disproportionately singled out. Blacks and Hispanics make up a little more than half of the city’s population but about 85 percent of the people stopped. Supporters of the program argue that minority men are disproportionately represented among offenders as well. But analyses dating back more than a decade have shown that it is not so simple.

As Judge Scheindlin notes in her opinion, a report by the legal scholar Jeffrey Fagan found that blacks and Latinos were more likely to be stopped at police discretion, not just in high-crime, high-minority areas, but in districts where crime is minimal and populations are mixed.

Police officials say that officers stop people when they have reasonable suspicion of criminal activity. An analysis last year by The Times of street stops in one mainly black Brooklyn neighborhood found that officers listed vague reasons in half the stops, including “furtive movement,” a category that can be used to mask harassment.

The Fagan report found that arrests are made in less than 6 percent of all street stops — a lower rate than if the police simply set up random checkpoints. Less than 1 percent of stops turned up weapons. This suggests that hundreds of thousands of people, mostly minorities, have been stopped for no legitimate reason — or worse, because of the color of their skin.

The Police Department says it has a training program that explains proper arrest procedure and warns officers against racial profiling. But Judge Scheindlin was sharply critical of those efforts, noting that numerous officers did not recall ever receiving such training.

In rejecting the city’s request for dismissal, Judge Scheindlin rightly pointed out that the suit, brought by the Center for Constitutional Rights, raises issues of great public concern. New Yorkers need to know whether the Police Department has failed to properly train and monitor its officers to prevent race-based stops.