WASHINGTON — Murder fell 6.5% in America’s largest cities during the first half of 2007, a sharp contrast with smaller cities, where murders rose 3.2%, according to a preliminary review by the FBI. Overall, murder declined by 1.1% throughout the USA during the first half of 2007, the report released Monday showed. Violent crime fell by nearly 2% nationwide with drops in every major crime category - including rape, robbery and aggravated assault - suggesting that some recent spikes in violence may be short-lived. Some law enforcement experts say one reason for the disparity in murder rates could be varying crime-fighting strategies, such as targeting juvenile offenders. ‘There is continued volatility, but there are cities that have made (enforcement) changes that are having a significant impact,’ says Chuck Wexler of the Police Executive Research Forum, a police advocacy group. ‘The latest numbers from the FBI are encouraging, though preliminary, and subject to change when the final numbers are released later this year,’ Justice Department spokesman Peter Carr said. ‘Some communities, however, continue to face violent crime challenges.’ In cities with populations between 50,000 and 99,999, murder rose 3.2%; in urban counties, murder rose nearly 5%. […]