The New York Police Department's "stop and frisk" tactic, under which millions of mostly black and Hispanic people have been questioned by police over the past decade, has violated constitutional rights, a federal judge ruled Monday.
The judge, Shira Scheindlin of Manhattan federal court, ordered an independent monitor to oversee the program. She pointedly did not order an end to the tactic.
Four men had sued the city, saying that they were unfairly targeted by police. The judge ruled that their Fourth and 14th Amendment rights had been violated. The Fourth protects against unreasonable searches, and the 14th guarantees equal protection under the law.
Scheindlin found that the police had used the tactic 4.4 million times between 2004 and 2012, and that 80 percent of the stops were of blacks and Hispanics.
"The City's highest officials have turned a blind eye to the evidence that officers are conducting stops in a racially discriminatory manner," the judge wrote. "In their zeal to defend a policy that they believe to be effective, they have willfully ignored overwhelming proof that the policy of targeting 'the right people' is racially discriminatory and therefore violates the United States Constitution."
To stop someone, the judge wrote, the police need more than an "unparticularized suspicion or hunch." And to proceed to a frisk, the officer must reasonably suspect that the person is armed and dangerous, she wrote.
The judge noted that the overwhelming majority of the stops - 88 percent - result in no arrests or tickets. But she emphasized that she was making no ruling about the effectiveness of the tactic in fighting crime, only on its constitutionality.
"Many police practices may be useful for fighting crime - preventive detention or coerced confessions, for example," she wrote, "but because they are unconstitutional they cannot be used, no matter how effective."
There was no immediate reaction from the city. Michael Bloomberg, the outgoing mayor, has forcefully defended the tactic.
"There is no doubt that stops are a vitally important reason why so many fewer gun murders happen in New York than in other major cities - and why we are the safest big city in America," he said in a speech in April.
Scheindlin stressed that she was not halting the "stop and frisk" practice, only trying to make sure that it was carried out in a way that protects the liberties and rights of New Yorkers.
She appointed an outside lawyer to study the program and report back to the court, and to issue public reports every six months.
The White House had no immediate comment on the ruling.