Under Giuliani NYC had WWB (Walking While Black/Brown) for males from their mid teen into their early thirties. This actually did have a huge effect on gun crime. The arrests were routinely tossed by the courts, but you didn't get your gun back, and those things are expensive, especially in NYC where handguns are virtually unobtainable through legal means. So folks started avoiding carrying guns unless they believed they would be likely to use them - lots less impulsive gun violence.

One of the UK's major initiatives in fighting the IRA during the 80's was the so called "Ring of steel" around the city of London. Vehicles entering the city could be stopped and searched. Guess what colour people made up the vast majority (In excess of 90%) of the arrests were that resulted from this policy.

Any idiot can face a crisis - it's day to day living that wears you out.