JOHN DeCARLO: "We had seen crime rates during the eighties that the country had literally never seen before. The violent crime rate and the property crime rate were exceptionally high. Criminologists across the United States had pretty much given up hope that police could have any effect on crime."

That crime wave included the so-called crack wars, the violent competition between drug dealers in the rise of crack cocaine.

FAITH LAPIDUS: In the nineteen nineties, the mayor of New York, Rudolph Giuliani, began a crime reduction program in the city. His first police commissioner, William Bratton, used ideas similar to what James Q. Wilson had been writing about. These included putting more police officers on foot instead of in cars. More attention went into targeting low-level criminals and keeping order in neighborhoods.

Professor DeCarlo says this was the beginning of a new way of operating within a police force.

JOHN DeCARLO: "When Bratton came into New York he concentrated on low-level criminals rather than higher-level criminals, thinking that taking care of the low level criminals would automatically take care of the higher-level criminals because, indeed, they were the same people."

BOB DOUGHTY: In nineteen ninety, New York had more than two thousand killings. That same year, William Bratton arrived as chief of the city's transit police. One of the things he did, says Professor DeCarlo, was to send more police officers into the subway system to arrest people for turnstile jumping. That is jumping over the fare gates without paying for a train ride.