Andrew Faas, a former senior executive with Canada's two largest retail organizations, found this out the hard way when he blew the whistle on a corrupt colleague, and subsequently had his phone and email hacked, and even received an anonymous death threat.
To help others, Faas says in his new book, "The Bully's Trap," that any worker being hired or promoted in a supervisory position should be required to take a psychological test.
What would it test for? The 20 signs listed in the Hare Psychopathy Checklist as developed by renowned psychologist Robert Hare.
A psychopath may not show all the signs, but they will likely demonstrate at least some of them, Faas says.
Here are nine signs that one of your coworkers may be a psychopath: