If you're working in a high-crime neighborhood, and you see...

If you're working in a high-crime neighborhood, and you see a person on a street corner hitching his belt up in a way that he would if he were concealing a handgun, you would want to examine that situation more closely. Or if you were patrolling a known drug-sales zone at three in the morning and saw somebody on their cell phone, you would want to look into that. But if you get to the fifth or sixth situation, and everybody that you have come across to this point has been black, you're going to second-guess yourself.