Three years have passed since a Federal District Court ruled that New York City’s stop-and-frisk program violated constitutional prohibitions against unreasonable search and seizure and discriminated against minority citizens, who were disproportionately and unjustifiably singled out for stops. A court-ordered reform process — overseen by an independent monitor — is off to a promising start. But some of the thorniest and most contentious issues lie ahead.

Under the Fourth Amendment, police officers can legally stop and detain people only when they have a reasonable suspicion that the person is committing, has committed or is about to commit a crime. In New York, however, it became common for police officers to stop mainly minority citizens, with no basis for suspicion, and then make up a reason.

In 2011, at the height of the program, the police stopped people on the streets an astonishing 685,000 times — up from just 97,000 a decade earlier. In practical terms, this meant that individuals in heavily policed neighborhoods could be stopped on the street without cause multiple times within a given year.

Plaintiffs in the case of Floyd v. City of New York, filed in 2008, alleged that the New York City police were stopping people on the basis of race, without justification. A statistical study of nearly 4.5 million stops produced at trial showed that only 6 percent of stops resulted in arrests and 6 percent resulted in summonses — which meant that 88 percent of the people stopped had been doing nothing wrong.