You're right, jabber; serial killers look like ordinary people. But there is no set look; remember, this is all going on inside these folks' heads. Even though they are profoundly disturbed, they may be able to function quite well as a 'normal' person and do what they do afterhours. We have all seen too many movies and think these guys -- nearly all men -- look like monsters. They don't, and it's scary.

I don't think it's useful to regard every man as a potential serial killer, but we all should remember that just because people seem nice doesn't mean they are. In fact, some of the best scams are perpetrated by people who pretend to be nice Christians -- and people fall for it because they believe nobody could sound that nice while they're reaching for your wallet. (I friend of mine's father got taken for several thousand dollars by people doing just this. Thank goodness his daughters moved quickly to shore up his finances. He was furious at first, but eventually got what they were saying.)