A man charged with a string of murders in western Canada this past October was described as “a normal guy” by those who knew him. It’s hardly the first time a dangerous person has seemed normal to acquaintances.

People typically trust their guts about those they meet. Unfortunately, our guts are not as good at evaluating people as we think they are. They’re overly influenced by…

Superficial details that suggest normalcy. If someone dresses well and has a nice home and an easy smile, your gut is likely to tell you that this must be a decent person.

Your outlook on life. If you’re naturally extroverted and optimistic, you are predisposed to believe that those you meet are well-meaning even when they’re not. If you’re naturally introverted and pessimistic, you’re predisposed to sense that new acquaintances have bad intentions even when they don’t.

Opinions of the new acquaintance shared with you by people you know. When people you know share their opinions of someone you don’t yet know, you’re likely to believe their assessments even if you have little or no evidence to back them up.

WARNING SIGNS

The following behaviors could be red flags that someone is dangerous and best avoided. Do not overreact to a single event—anyone can have an out-of-character moment. But be wary of patterns and recurrences of…

Inappropriate anger. Be extremely concerned if you witness outbursts of anger from a new acquaintance. Example: A coworker you carpool with but don’t know well screams at other drivers.

People generally do their best to control their anger when they’re around those they don’t know well. If this person cannot rein in his anger around you now, his anger might reach dangerous levels later, when he knows you better.

Publicly embarrassing others. Someone who dresses down another person in public could lack sufficient empathy to truly care about anyone else—including you. Example: A new acquaintance berates a waiter for a mistake so loudly that other tables hear.

Reducing people to groups and referring to those groups negatively. Those who make sweeping, negative statements about large groups of people—such as races, genders or specific social circles—usually are bad news even if you’re not a member of a group they bad-mouth. People who think this way tend to be equal-opportunity haters. Allow them into your life, and they will likely find a reason to hate you, too.

Impulsivity. On its own, impulsivity is not necessarily a bad trait, but when it’s paired with anger or arrogance, the result can be extremely dangerous. Example: An angry person might yell at another driver on the highway…an angry and impulsive person might try to cut that other driver off at 70 miles per hour.

Collecting perceived injustices. Some people see their lives as a never-ending string of wrongs being done to them. They never forget any perceived sleights, and on occasion, they lash out with retaliations that seem totally out of scale with the situation. In their minds, their retaliations are justified because they are in response to many wrongs, not just the most recent one. Avoid people who chronically complain about a litany of wrongs that have been inflicted upon them. You don’t want to be around when these people lash out. Example: After someone parks in her parking space, a coworker goes on a long diatribe about how no one respects her.

Psychopathic tendencies. Psychopaths are pathological liars. They’re demanding, impulsive and thrill-seeking. They do not take responsibility for their actions—they lack feelings for others and have no conscience. Yet they often are extremely glib and charming. It can be very difficult to identify a psychopath, particularly if you don’t spend much time around this person. But if you start to see a pattern that matches this description, the safe course is to stay away.

CUTTING TIES

If someone in your life is potentially dangerous, you need to distance yourself from him/her—without causing offense. This might be as simple as no longer socializing with this person, but in some cases, cutting ties is complicated. Here’s what to do when the potentially dangerous person is…

Your neighbor (or someone else you cannot completely remove from your life). Avoid contact with this person when you can, and minimize the interaction when you cannot. Your inclination might be to confront a problem neighbor about his misbehavior or try to help him with his problems, but the wiser course is to offer a polite greeting when you happen to see this person—then walk away as soon as you can without being rude. If this neighbor’s behavior becomes unbearable, go to a legitimate entity that can intervene on your behalf, such as a homeowners association or even the police, if necessary.

Warning: Do not band together with other neighbors to confront a problem neighbor as a group. That could put the group spokesperson in danger.

A household worker. Pay for any work that has already been done without any criticism or negative comment. Come up with an explanation for why you do not require this person’s continued services that does not demean this person. Example: A man I hired to mow my lawn destroyed my expensive landscaping lights. The anger I saw from this man told me that he was potentially dangerous, so rather than confront him about the terrible work he did, I paid his bill and casually told him that I had decided to cut my grass myself in the future. I even sent him a note thanking him.

Driving a car you’re riding in, such as in a carpool. If you fear for your safety, come up with an excuse why you need to get out of the car immediately. Example: “I’m feeling carsick. I don’t want to ruin your upholstery. Pull over quick.” Once you’re out of the car, say that you’ll walk to your destination or arrange another ride.

Your coworker. Contact human resources, the employee assistance department or your immediate supervisor and describe your concerns. Ask that your name be kept out of it if the company pursues the matter with the employee.

An employee you need to fire. Treat the employee with respect. Never be derogatory or insulting. Go out of your way to make him feel cared for—pay severance and pay for a job-finding service, if possible. Some type of follow-up action also is important. Check in on the former employee to address any concerns he may have.

Stalking you. If you have repeatedly asked this person to leave you alone, yet he persists, it’s time to stop speaking to him. The natural inclination is to tell this person to leave you alone again, but to a stalker, even this negative attention still is more welcome than no attention. If the stalker approaches you at a business, such as your gym or a restaurant, walk away without a word.

Important: If the stalker’s behavior continues and/or appears to be escalating or becomes more erratic and/or strange, this requires law-enforcement intervention. The law-enforcement expert will discuss strategies with the victim, including a restraining order. However, the victim must understand that restraining orders do not intimidate some stalkers. Victims and their families and friends need to keep records of any and all communications. Throw nothing away. This is the kind of record that will become essential if the case goes to court.

Source: Mary Ellen O’Toole, PhD, a recently retired FBI profiler who now teaches at the FBI National Academy, Quantico, Virginia. While with the FBI, she worked on many high-profile cases, including the Unabomber and Green River Killer cases. She is author of Dangerous Instincts: How Gut Feelings Betray Us (Hudson Street). www.DangerousInstincts.com