The Statistical Debate Behind the Stop-and-Frisk Verdict

As all the world now knows, Judge Shira Scheindlin has ruled that the New York City Police Department’s stop-and-frisk policy amounts to “a policy of indirect racial profiling” that violates the U.S. Constitution. But how did the she reach this conclusion? The answer turns out to be pretty interesting. It involves a number of statistical studies presented to the court by expert witnesses for the plaintiffs (a number of New Yorkers who claimed to have been stopped and frisked without cause) and the defense (the city of New York).

From my reading of Judge Scheindlin’s opinion, which runs to almost two hundred pages, and a brief perusal of some of the expert testimony, the court’s decision seems like the correct one. (Like many New Yorkers, I think the stop-and-frisk policy went way too far and, in some neighborhoods, degenerated into racial harassment.) Still, Judge Scheindlin’s ruling isn’t without its quirks. In one instance, she criticized the conclusions of the plaintiffs’ expert witness; in another, she endorsed the same expert’s work and relied upon it to justify her ruling that stop-and-frisk is indirect racial profiling. If and when the city goes forward with its appeal, the methodology of the studies, and the interpretations that Judge Scheindlin placed upon their conclusions, are sure to be central issues. (For more on Scheindlin, see the piece that Jeffrey Toobin wrote for the magazine about her and the case earlier this year.)

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