NEW YORK - July 11, 2010 - When night falls, police officers blanket some eight odd blocks of Brownsville, Brooklyn. Squad cars with flashing lights cruise along the main avenues: Livonia to Powell to Sutter to Rockaway.

On the inner streets, dozens of officers, many fresh out of the police academy, walk in pairs or linger on corners. Others, deeper within the urban grid, navigate a maze of public housing complexes, patrolling the stairwells and hallways.

This small army of officers, night after night, spends much of its energy pursuing the controversial Police Department tactic known as “Stop, Question, Frisk,” and it does so at a rate unmatched anywhere else in the city.

The officers stop people they think might be carrying guns; they stop and question people who merely enter the public housing project buildings without a key; they ask for identification from, and run warrant checks on, young people halted for riding bicycles on the sidewalk.

One night, 20 officers surrounded a man outside the Brownsville Houses after he would not let an officer smell the contents of his orange juice container.

Between January 2006 and March 2010, the police made nearly 52,000 stops on these blocks and in these buildings, according to a New York Times analysis of data provided by the Police Department and two organizations, the Center for Constitutional Rights and the New York Civil Liberties Union. In each of those encounters, officers logged the names of those stopped - whether they were arrested or not - into a police database that the police say is valuable in helping solve future crimes.