Whoever Fights Monsters: My Twenty Years Tracking Serial Killers for the FBI

Robert K. Ressler, a former FBI Supervisory Special Agent, a senior agent who oversaw investigations, recounts his 20-year career investigating and interviewing serial killers. Ressler traces the development of the FBI's Behavioral Sciences Unit (BSU), the profiling techniques he helped create, and the personal toll of decades spent studying the criminal mind. The book takes its title from a Friedrich Nietzsche quotation warning that those who fight monsters must take care not to become monsters themselves.

Ressler opens with the January 1978 case of Richard Trenton Chase, the "Vampire Killer." A young pregnant woman, Terry Wallin, was found murdered in her Sacramento home with organs removed and evidence of blood consumption. Ressler constructed a profile: a white male in his mid-twenties, thin, mentally ill, and living alone. He bases these conclusions on the crime scene's "disorganized" characteristics, a classification distinguishing methodical killers from those driven by psychotic delusion. After three more murders nearby, Ressler predicted the killer lived within one-half to one mile of the abandoned getaway vehicle, and a former classmate's identification led to Chase's arrest. Ressler stresses that profiles do not catch killers but narrow the search. Ressler interviews Chase on death row, where Chase claimed he killed to replenish blood he believed was turning to powder and described persecution by Nazis connected to UFOs. Chase died in late 1980 from an overdose of hoarded pills.

Ressler traces his path to the FBI. As a nine-year-old in 1946, he became fascinated by the case of William Heirens, a teenager who killed three people in Chicago. This interest persisted through his Army military police service and education at Michigan State University. After joining the FBI in 1970 and completing field assignments, he transferred to Quantico in 1974 to study under profiling pioneers Howard Teten and Pat Mullany. At a British police academy, he coined the term "serial killer" after hearing lecturers discuss "crimes in series," connecting the concept to the killer's compulsion to refine each crime.

Frustrated that the FBI relied on secondhand information, Ressler arranged unauthorized prison interviews in California with agent John Conway in early 1978, interviewing seven convicted killers including Sirhan Sirhan, Charles Manson, and Edmund Kemper. When discovered, he framed the work as a pilot study. His formal proposal for the Criminal Personality Research Project was initially rejected but later approved by new Director William Webster, who insisted on collaboration with universities.

Ressler describes the dangers of interviewing killers. During a solo session with Kemper, imprisoned for multiple murders, the guard failed to respond to the buzzer, and Kemper remarked he could twist Ressler's head off before anyone arrived. Realizing he had fallen prey to Stockholm syndrome, identifying psychologically with a captor, Ressler bluffed through the encounter and subsequently required interviewers to work in pairs. From Manson, Ressler learns how the cult leader built his following by mirroring his followers' desires, concluding that Manson did not directly order the 1969 Tate-La Bianca murders in Los Angeles but created the climate in which his disciples knew what was expected. David Berkowitz, the Son of Sam killer, admitted that his claim about a demon-possessed dog was fabricated and that he returned to crime scenes to relive the murders sexually.

The Criminal Personality Research Project, conducted with Dr. Ann Burgess of Boston University, interviewed 36 incarcerated murderers. The findings challenge popular assumptions: Subjects often grew up in outwardly stable families concealing dysfunction, yet half had mental illness in the immediate family, nearly 70 percent had familial substance abuse, and every subject experienced serious emotional abuse in childhood. Ressler argues that fantasy, not trauma alone, drives the progression to murder. These fantasies fused sexual desire with destructive impulses and escalated through a feedback loop in which unpunished antisocial acts fed increasingly violent scenarios. Precrime stresses, such as the loss of a job or relationship, served as the final trigger.

In the 1983 murder of 13-year-old newsboy Danny Joe Eberle in Bellevue, Nebraska, Ressler profiles the killer as a youthful white male with a chronic sexual problem. After a second boy was murdered, Ressler suggested the killer might be stationed at nearby Offutt Air Force Base. A day-care teacher's alert led police to Airman First Class John Joseph Joubert IV, a 21-year-old radar technician and assistant scoutmaster who fit the profile. Joubert confessed, revealing fantasies of cannibalism dating to age six, and was later connected through bite-mark evidence to an unsolved murder in Maine.

Ressler explains the organized versus disorganized classification that became the BSU's fundamental profiling framework. Organized offenders plan crimes, target strangers, bring and remove weapons, take trophies, and conceal bodies. Disorganized offenders act on psychotic impulse, attack randomly, and make no effort at concealment. He illustrates these types through Gerard Schaefer, a Florida police officer who methodically lured and killed women, and Herbert Mullin, who had paranoid schizophrenia and killed 13 people driven by delusions that human sacrifices would prevent an earthquake.

Several cases demonstrate profiling's practical value. Ressler's profile of Francine Elverson's killer in the Bronx led investigators to Carmine Calabro, a former mental patient in the victim's building. After President Reagan was shot by John Hinckley, Ressler predicted what agents would find in Hinckley's motel room, including evidence of Hinckley's fixation on actress Jodie Foster, for whom Hinckley said he carried out the shooting. Ressler also examines deliberate staging. During a strangulation series in Columbus, Georgia, letters purportedly from white vigilantes claimed to hold a Black woman captive; Ressler determined they came from a single Black male who had already killed the woman, leading to the arrest of William Hance, a soldier at Fort Benning. At the British police college, Ressler declared a tape purportedly from the Yorkshire Ripper a hoax and profiled the actual killer as an introverted truck driver; Peter Sutcliffe, a truck driver, was caught in 1981.

The case of Oregon killer Duane Samples illustrates the dangers of premature release. Samples, a Vietnam veteran, murdered a woman by disemboweling her in 1975. When the governor commuted his sentence based on Samples's claim of combat-related Post-Traumatic Stress Disorder, Ressler discovered that the soldiers Samples said he watched die were both alive and that Samples's records showed no medals for bravery. The governor reversed the commutation.

Ressler recounts the development of the Violent Criminal Apprehension Program (VICAP), a computerized system for linking violent crimes across jurisdictions conceived by Los Angeles detective Pierce Brooks in the 1950s. Ressler convinced Brooks to house the program within the FBI and helped establish the National Center for the Analysis of Violent Crime (NCAVC), announced by President Reagan in 1984. Implementation was hampered by bureaucratic misallocation, but Ressler argues the system could significantly reduce unsolved homicides if participation were mandated.

At the first International Homicide Symposium at Quantico in 1988, Ressler recounts a live satellite broadcast in which 300 law-enforcement officials watched interviews with John Wayne Gacy, a convicted serial killer, and Kemper. Kemper spoke candidly about the role of fantasy in his crimes, while Gacy used his time to argue his innocence.

In the final chapter, Ressler reflects on his broader influence, including outreach to the psychiatric community and serving as a resource for Thomas Harris, whose novels Red Dragon and The Silence of the Lambs draw on BSU materials. After retiring, Ressler testified in the Jeffrey Dahmer case, concluding that Dahmer, who killed 17 males and engaged in cannibalism and necrophilia, represents a "mixed" offender combining dynamics usually seen separately. Ressler argues against the death penalty for serial killers, contending that executions do not deter future murderers and prevent researchers from studying subjects whose insights could help prevent future crimes.