Few developments in the field of public policy in American have engendered as much controversy as the question of why crime declined so dramatically in New York City in the past two decades.  Berkeley Criminologist Frank Zimring characterized the decline of the past decade  as a “Guiness book of records” achievement, and attributed the drop to an enforcement  practice called “hot spot” policing. Hot spot policing buildings on the police management innovations called “community problem solving policing” and it data driven successor, Compstat, focuses even greater deatPerhaps because many policy analysts in  the field of crime shared David Bayley’s belief, expressed in his book, The Police  of the Future (1994), that the police “cannot prevent crime,” Zimring’s  attribution of the decline to innovative police practices in The City that Became Safe (2012) has to contend with many others: Did crime in New York really decline, or were the numbers fudged?  If it did  decline was  it because the economy improved, the crack epidemic ended, Roe v. Wade changed the demography of cities, more offenders were incarcerated, or lead poisoning from gasoline declined, reducing it harmful effects on the mental conditions associated with criminal behavior? This paper  by a political scientist who has long studied police management, a quantitatively trained policy scholar, and an urban historian specializing in crime and safety in public housing,  using the most extensive data on NYC crime and NYPD  practices available, presents  an analysis of ten years of  hot spot policing in New York, testing “hot spot policing” against the many rival hypotheses,  to solve the mystery of  the New York City crime decline. Of necessity, the evaluation will address controversies surrounding the model of proactive policing that has led to political and legal challenges.