A federal judge has ruled that the New York City Police Department's controversial "stop-and-frisk" crime-fighting tactics violate the US constitution.
District Judge Shira Scheindlin on Monday ruled in favour of four men who said they were unfairly targeted.
She said the city police adopted a policy of "indirect racial profiling" by targeting racially defined groups for stops.
Police have made about 5 million stops over the past decade, mostly of black and Hispanic men.
The practice has become "a fact of daily life in some New York City neighbourhoods,'' Scheindlin said in her ruling.
The class action was considered the broadest legal challenge to stop-and-frisk, a tactic in which city police stop people they suspect of unlawful activity and frisk those they suspect are carrying weapons.
Scheindlin's decision follows an exhaustive nine-week trial that pitted the NYPD's interest in keeping New York's crime rate down against black and Latino plaintiffs who felt discriminated against.
As part of her ruling, Scheindlin ordered the appointment of an independent monitor to oversee compliance with other remedies she ordered.
The other remedies include the NYPD adopting a written policy specifying circumstances where stops are authorised; adopt a trial programme requiring the use of body-worn cameras in one precinct in each of the city's five boroughs; and to set up a community-based remedial process under a court-appointed facilitator.
Mayor Michael Bloomberg and NYPD Commissioner Raymond Kelly have defended the practice as a life-saving tool, limiting the number of illegal guns being carried on the streets on New York.