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. And again…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 LZczdiberties 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.