How to Spot Psychopaths

Scenario 3: Your son Max has made a new friend, Steve, and wants to spend the night. You don’t know Steve’s family.

After buying some time, you need to meet the friend’s parents, O’Toole suggests. Even then, if they “seem nice” and have a well-mowed lawn, that doesn’t mean they don’t have unlocked guns lying around, own a pet cobra, text madly while driving, or have creepy Uncle Biff living in the basement. Get to know the parents. Check local registered sex offender lists and dangerous dog registries (the book has a chapter on such resources). Check out family members’ MySpace or Facebook pages. Visit the house; if you see mounted deer heads, that opens the door to ask about hunting and guns.

Scenario 4: A uniformed telephone repairman is at your front door, but you don't have an appointment. The last time you let in a repairman, everything went fine—and you don’t want to seem rude.

O’Toole brings up the case of Joe LaRette, who posed as a telephone repairman to get into women’s homes, whereupon he sexually assaulted and/or murdered them. Among the questions O’Toole suggests asking yourself are: Are you expecting someone? How easy would it be for him to push his way in? Are you alone? If not, is there someone there (like a child), you’d want to protect (making you more vulnerable)? Is there a way to verify the person’s identity without opening the door—for example, by calling the company? Does he have anything in his hands that could be used as a weapon?

She says that we tend to think that other people are like us, not looking to hurt others. That’s not, alas, true. Her bottom line advice: “I would recommend not opening the door at all. Anyone with a legitimate reason to be there will leave a note or follow up with a phone call. Although this might seem rude, consider that your safety is more important than whether the company gets the job done that day.”

Know how your mind works! Profiler Mary Ellen O’Toole lists five common ways you undermine your perception of people:

NORMALIZING: finding an explanation for risky behaviors. Example: Your daughter’s boyfriend complains angrily about his job and has been practicing at a shooting range. You tell yourself he’s just letting off steam.

RATIONALIZING: A strange car is parked in front of your house for hours with a man sitting in it. You decide not to call the police because you don’t want them to think you’re overreacting.

EXPLAINING IT AWAY: The parents of a missing child turned that child’s bedroom into an office shortly after the disappearance, O’Toole says. The police had decided they weren’t suspects and explained it by saying that the house was small, and they needed a “nerve center” to manage the search efforts. (The child, says O’Toole, was never found.)

IGNORING: Denial or willful blindness on the part of parents, for example, whose school-age child is alienated and looking up bomb-making online.

ICON INTIMIDATION: Bernie Madoff looked prosperous and had rich and famous clients who swore by him. A nice suit, good grooming, and a smile, not to mention family connections or a good job, can go a long way toward fooling you.

MORE: When You Go With Your Gut