At best, the police goal is to look like they're "doing something". Suppose the police know that a particular criminal drove a green Chevy. If 90% of the green Chevrolets in an area were bought locally, and if the police harass 90% of the owners of locally-purchased green Chevrolets until they come up with alibis, then by liberaLogic, since the police have checked out 81% of the green Chevies, they're 81% of the way toward solving the case. Of course, even if the police tracked down 99% of Chevy owners and 99% of those had alibies that checked out, the police would be 98% through with the case, and yet no closer to actually solving it than before they began.
You are so right and you know it! Let's do nothing until the wacko shoots your children...