When I began researching my new book, which features a team of FBI agents hunting a serial killer, I had to dig into the real story behind the FBI’s famous Behavioral Analysis Unit. There have been many fictionalized accounts of these agents and the work they do, beginning with Thomas Harris’s The Silence of the Lambs in 1988. Newer incarnations include several movies and television shows.

To create a fresh take on this type of criminal investigation for my novel, I pulled together a hybrid FBI team that does not actually exist. Writing fiction, however, demands that even the highest flight of fancy on the part of the author must be grounded firmly in fact. With that thought, I put my nose to the grindstone and used my law enforcement background to do hundreds of hours of research.

I started at the beginning, looking into the writings of those who began the program, which actually didn’t officially become a standing unit for more than ten years. The idea behind this kind of criminal profiling had its inception around 1960 when Agent Howard Teten became convinced he could figure out suspects’ personalities by examining the scenes of their crimes. He began reviewing police reports of homicides from around the country. After an arrest, he would compare the predicted personality traits to those of the actual perpetrator, continuously honing his skills. He eventually teamed up with Agent Patrick Mullany, who was an expert in abnormal psychology, to teach these concepts to others in law enforcement.

In 1972, Agents Robert Ressler and John Douglas added their own efforts to understanding what drove violent killers to repeatedly commit their crimes. Simply saying, “Well, they’re obviously insane,” wasn’t good enough. If the psyche of the offender could be grasped, then it might prove possible to predict the patterns and practices of future offenders—and to apprehend them faster.

This monumental task began with a series of interviews of incarcerated murderers. It is Agent Ressler, in fact, who is credited with coining the term “serial killer.” Agents Ressler and Douglas would go to penitentiaries around the country and ask to speak to these killers in person. So much more can be gleaned from direct contact that is lost when reading written statements. The only caveat was that these offenders had to be willing to talk. Fortunately, most were.

What those pioneering agents discovered was nothing short of fascinating. They were able to break criminal behaviors down into categories. At first, broad groupings such as “organized” and “disorganized,” then eventually into more categories such as power and control, visionary, mission-oriented, and hedonistic. These classifications continue to be refined to this day.

The agents pored over their interviews after going back to Quantico (where the BAU was called the BSU and used to be housed in the basement) and created a database to help law enforcement officials from around the world narrow down their suspect pools and solve cases.

One of the most daunting issues in solving an ongoing series of crimes—especially ones that grab headlines—is the tremendous volume of potential suspects. The public often mistakenly believes that coming up with a suspect is the biggest hurdle. Often, the opposite is true, and winnowing down the list is what will garner the most effective results and avoid wasting thousands of personnel hours and taxpayer dollars chasing down leads and researching alibis. Behavioral analysis offers an efficient method to take hundreds of suspects and pare them down to a manageable number quickly.

Several years ago, I went to Quantico to attend a class on serial killers designed for law enforcement investigators. The class was a 40-hour, one-week crash course. The instructors were seasoned FBI profilers. By this time, I had several years on the job and had seen my share of dead bodies, some in appalling condition. I was not so much repulsed by the visual images of carnage as by the twisted minds behind the grisly scenes and macabre rituals.

It was a disturbing exposé of man’s inhumanity to man.

During the class, we reviewed scores of the worst cases from some of the most prolific and deranged killers in our nation. After a while, I kept coming back to one question: How could someone do that to another human being? I found that my outrage slowly morphed into numb disbelief.

This is why the FBI criminal profilers, those we call mind hunters, are my heroes. They not only examine scenes; they put themselves into the mind of the killer. Equally important, they must also put themselves in the mind of each victim. To catch a killer, it’s critical to know how he interacts with his victim and how his victim interacts with him. In order to do that, the profiler must be willing to immerse themselves into the depravity of a killer and the agony of a victim.

Over and over again.

I was not surprised to learn that it often takes a toll on their private lives and their families. Some of them develop a form of what I will call “PTSD by proxy.” They may not have been the direct victims of the perpetrator, but they absorbed every aspect of the crime from both the victim’s and the killer’s perspective. What may have taken a perpetrator fifteen minutes to do, a profiler will spend hundreds of hours examining in excruciating detail.

The job of a mind hunter is not glamorous. It’s a grueling, often thankless task that will have no end as long as human beings walk the earth. We can all be grateful, however, that there are those men and women who are uniquely called to perform this service at great personal cost. Today, I honor them.