The incident was over in a matter of minutes. But two weeks after the beating of a black motorist by Los Angeles policemen was videotaped by an eyewitness, it had led to arrests, probes by local, county and federal organizations and a Justice Department review of law-enforcement violence across the nation.
It began with wailing police cars chasing a motorist through the night, cornering his car in a Los Angeles suburb and surrounding the driver as he stepped into the street. A sergeant fired a 50,000-volt Taser stun gun at the unarmed black man, then three officers took turns kicking him...