Joan Arehart-Treichel is an award-winning science writer who, over the years, was on the staff of Science News Magazine; has written articles about scientific advances for New York Magazine, Glamour, Harper’s Bazaar, Psychology Today, Sexology, The Washington Post, and other consumer publications; and has written four previous books about scientific advances for the public, notably Biotypes: The Critical Link Between Your Personality and Your Health, which was published by Times Books (The New York Times book publishing company) and sold in the United States, Canada, England, and France.

For 15 years, she worked as a senior staff writer for Psychiatric News, a newspaper published by the American Psychiatric Association for psychiatrists throughout the United States. During this period, she covered research advances in various domains of psychiatry, including forensic psychiatry. And during her coverage of forensic psychiatry, she came to know a number of leading authorities on evildoers, many of whom are prime sources in Warding Off Evildoers. She also had face-to-face contact with some individuals who had committed grisly deeds. Her book is thus based on what she has learned about evildoers during this time period—information that she believes is not just provocative, or frightening, but that could help people shield themselves from such individuals.