the point is that it's not a useful indicator for stopping random people. "Oh, to catch the thief we are going to stop 100000 people" sounds absurd, after all.

the point is that it's not a useful indicator for stopping random people. "Oh, to catch the thief we are going to stop 100000 people" sounds absurd, after all. Of course you can use the clue to exclude a bunch of people, but were you going to go around arresting random people on the street without this? Of course not, so why do it after.