When you meet someone for the first time, you have a tendency to look at certain features first. Some people (very shallow ones) will base their entire interpretation of what a person is going to be like based on this first impression. I know for myself, I have a tendency to look at the eyes first. I remember an advertisement from many years ago where the spokeswoman had amazing grey eyes. I was almost willing to use the product for that reason alone. It has been said that, "The eyes are the window to the soul." Whether that is true or not, I believe that eyes do tell us a great deal about the person they belong to. I have a little kids program on my PDA that allows them to draw faces. It gives them different choices of facial features to choose from, and they can create many different combinations. I have noticed that among the eye choices their is one set that I call the "evil eyes". No matter what goofy mouth, hair, ears, or nose you put on the face, as soon as you add the "Evil Eyes", that face is evil.
People you meet on the street are like this too. They may not be a bad person, and you certainly shouldn't judge them from a passing glance, but often you can see the "Evil" in them, at least at that moment. Maybe they have had a bad day. Maybe they are upset. Maybe they really are a bad person, but for that moment you can see exactly what they are. Some people have written about studies of psychopathic people, and one thing that they note is the lack of feeling and expression in these individuals, and this is why they are so successful at the things they do, no one suspects them, because they can't see the evil in them.
As a teacher, I can often see the guilt, or whatever, in my students long before I can prove anything. I try not to judge them, but they usually prove themselves out through their actions.
Keep your eyes open. I 've got mine on you. Take care.