Actually, a large part of Guillani's statistical success was created by adopting methods similar to Great Britian, and other European Nations. They simply re-defined crimes! By re-defining what it took to be classified as a felony, the felony murder rate dropped. Unintentional homicide, and accidental deaths rose. They did the same with felony assaults, reclassifying many as simple misdemenor assaults, and domestic disturbances.
The FBI even has a disclaimer posted with their stats now, because of "differences" in the manner crimes are now classified and reported by different states and cities.