Inside the Serial Killer’s Mind: How Modus Operandi Reveals Behavior
The methods serial killers employ to commit their crimes offer us a glimpse into how these individuals plan, think, and exert control over their victims. The serial killer’s modus operandi shows evolutionary behavioral patterns that reflect the experiences gained and refinement of personal preferences throughout their killing series. Methodologies include aspects such as victim selection and surveillance, weapon selection/killing method(s), and body disposal.
Beyond the primary motivation to kill, the interplay of personal characteristics, including an offender’s childhood, age, intelligence quotient, individualized gendered experiences, and socio-cultural identity, shapes the offender’s approach to serial homicide. Examining these interconnections helps law enforcement develop targeted homicide investigative strategies.
Obscurix promotes a holistic interpretation of crime data and recognizes the importance of utilizing inclusive, interdisciplinary approaches to crime analysis. The integration of forensic science, psychology, and criminology within research helps capture modern crime patterns most accurately.
Obscurix remains committed to keeping our audience informed of crime trends. We will likely supplement these findings at a later date when more data becomes available. Please be aware that the following analysis may not fully encompass the methodologies and characteristics of all serial killers within the United States and worldwide.
Most Common Serial Killer Methodologies and Killing Methods (U.S. & Worldwide)
According to a 2023 Annual Report on serial killer statistics published by Radford University in conjunction with Florida Gulf Coast University, the three most common methods of serial killing in the United States were gunshot (43.8 percent), strangulation (20.8 percent), and stabbing (15 percent).
Close-Contact Killings: What Strangulation, Bludgeoning, and Stabbing Reveal About Offenders
Killing methods such as strangulation or bludgeoning require a high degree of proximity as compared to alternative methods. The power and control exhibited by these techniques suggest these killings are more personal to the offender in a manner not as outwardly apparent when other methods are utilized. According to Uncovering Serial Killers, published by the College of Southern Idaho, Ted Bundy’s method included examples of such up-close killing strategies.
Bundy used his strength to physically overpower, subdue, and sexually assault his victims. Offenders who present with sadistic tendencies naturally gravitate toward methods more likely to draw out the killing process because the abuse and systemic torture of their victims facilitates the excitement they seek. The “Toolbox Killers”, Lawrence Bittaker and Roy Norris, exemplified this pattern. According to the Justia Law, Bittaker and Norris tortured their teenage victims with items such as a sledgehammer, an ice pick, and pliers before killing them.
The category of strangulation includes hanging, instrument/ligature, and manual strangulation. This was based on data that encompassed 11,678 American victims of serial killers, further broken down by the following methods of death within the Radford/FGCU Serial Killer Database:
| Primary Method of Death of American Serial Killer Victims (Historically) | ||
|---|---|---|
| Method of Death | Number of Victims | Percent |
| Shot | 5,117 | 43.8 |
| Strangled | 2,427 | 20.8 |
| Stabbed | 1,757 | 15.0 |
| Bludgeoned | 1,158 | 9.9 |
| Poisoned | 748 | 6.4 |
| Axed | 150 | 1.3 |
| Drowned | 112 | 1.0 |
| Smothered | 88 | 0.8 |
| Burned | 68 | 0.6 |
| Ran Over | 25 | 0.2 |
| Drug Overdose | 18 | 0.2 |
| Neglect & Abuse | 10 | 0.1 |
Guns, Distance, and Detachment: The Psychology Behind Serial Shooters
Serial killers who shoot as their killing method demonstrate an element of detachment by physically distancing themselves from their victims. This could be a risk-aversion strategy stemming from insecurity in their own ability to overpower their victims successfully, as a gun can be used to quickly and effectively incapacitate a victim while minimizing risk to the killer. American serial killers utilize firearms to kill their victims far more frequently than serial killers in other countries — 36.7 percent vs. 13.1 percent, comparatively.
In contrast, weapons such as knives may be easier to acquire but require increased proximity to the intended victim.
According to People, Ed Gein, the “Butcher of Plainfield,” shot two of his victims. He also robbed gravesites. Gein’s interests were disturbingly geared toward his macabre use of human remains as household items and decorations, not pre-death antics. This killing method allowed him to effectively neutralize the threat posed by his victims when they were alive, and quickly shift his focus to what he could accomplish after their deaths.
Interestingly, serial killers do not always utilize the same primary killing method for each of their victims. In fact, 36.8 percent of American serial killers employed more than one method across their killing series, in comparison to other countries at 26.8 percent. For example, John Wayne Gacy stabbed his first known victim, but later preferred strangling his victims, as noted in Uncovering Serial Killers. This rendered his first victim an exception to a modus operandi that emerged throughout his series of murders.
Age and Evolution: How a Serial Killer’s Methods Change Over Time
The Radford/FGCU conducted an age analysis on 5,252 serial killers by compiling data on age at the time of first kill. Of this sample, 3,579 offenders were from the United States, and the remaining 1,673 offenders were from other countries. Their findings indicated that, on average, serial killers were 28.1 years old when they committed their first murder and 33.6 years old at the end of their killing series. The median age of serial killers at the time of their first kill was 26 years old, with a standard deviation of 9.4 years. The oldest age at the beginning of a killing series was 72, with the youngest being 6 years old.
Variation in impulse control and psychological development may explain why younger serial killers gravitate toward different killing methods than their older counterparts. The killers who were youngest during their first kill, generally between the ages of 25 and 26, were more likely to employ stabbing/shooting methods (both elements present, average age of 25.2). Younger killers were also more likely to use bludgeoning/stabbing techniques (both elements present, average age of 26.2) or just shooting (average age of 26.5 years old).
Older serial killers tended towards strangulation (average age of 29.6), poisoning (average age of 34.8), and bombing (average age of 37.6) for their first killing.
Victimology profiles indicated that serial killers who targeted elderly victims had the highest average age at the start of their killing series at 31.2 years old, compared to offenders who target younger demographics.
How Serial Killers’ Age and Motive Type Correlate
Serial killers motivated by their involvement in criminal enterprise and gang-related activities were, on average, the youngest offenders across motive categories at the time of their first kill, 23.6 years old. Hedonistically motivated serial killers, categorized under enjoyment (element of rape present), were older at the initiation of their killing series, at age 28.9, compared to those with other primary motives for serial homicide. Additionally, serial killers who engaged in mutilation, torture, and necrophilia were, on average, only 2 years older than offenders who did not engage in these unusual behaviors.
| Average Age of Serial Killer Per Killing Method(Based on a dataset of 5,252 serial killers, 3,579 from the United States, 1,673 from other countries) | |
|---|---|
| Method of Killing (May Contain Multiple Components) | Average Age of Serial Killer |
| Stab/Shoot | 25.2 years old |
| Bludgeon/Stab | 26.2 years old |
| Shoot | 26.5 years old |
| Strangle/Shoot | 27.5 years old |
| Bludgeon/Shoot | 27.6 years old |
| Stab | 27.1 years old |
| Strangle/Bludgeon | 28.5 years old |
| Strangle/Stab | 28.0 years old |
| Bludgeon | 29.2 years old |
| Strangle | 29.6 years old |
| Poison | 34.8 years old |
| Bomb | 37.6 years old |
Gendered Differences In Killing Methods In the United States (Historically–2023)
In the United States, male serial killers are more likely to shoot or strangle than female serial killers. Female offenders use poisoning as their primary killing method significantly more than their male counterparts, observed in 54.5 percent of killings vs. 2.4 percent, comparatively. At the start of their serial killing series, male serial killers were an average of 4 years younger than their female counterparts at the time of their first kill.
| Killing Methods Used By Males and Females - Overall Percentage(United States, Historically–2023) | ||
|---|---|---|
| Killing Method | Male Offenders | Female Offenders |
| Shoot | 35.2 Percent | 19.1 Percent |
| Strangle | 15.3 Percent | 4.5 Percent |
| Stab | 11.3 Percent | 7.8 Percent |
| Stab/Shoot | 7.7 Percent | 3.5 Percent |
| Bludgeon | 7.6 Percent | 3.8 Percent |
| Strangle/Stab | 4.8 Percent | 1.0 Percent |
| Bludgeon/Stab | 4.7 Percent | 3.3 Percent |
| Bludgeon/Shoot | 3.9 Percent | 1.3 Percent |
| Strangle/Bludgeon | 4.0 Percent | 0.5 Percent |
| Strangle/Shoot | 2.9 Percent | 0.8 Percent |
| Poison | 2.4 Percent | 54.5 Percent |
| Bomb | 0.2 Percent | 0.0 Percent |
The IQ of Serial Killers: Intelligence, Motive, and Method Selection
The Radford/FGCU researchers obtained publicly available IQ scores on 323 serial killers, 298 of whom were from the United States and 25 were from other countries. Clearly, this is a limited sample size, and Obscurix recognizes the limitation of not having access to IQ data on all serial killers in the United States and worldwide. We also recognize that IQ fluctuates within individuals and lower IQ scores are easily faked.
In the general population, the “normal” IQ range is considered to be between 85 and 115, based on a mean IQ score of 100 and a standard deviation of 15 points. Based on known IQ data on serial killers, “the average IQ for a serial killer is 92.7 with a median of 85 and a standard deviation of 24.4.” This indicates that the typical IQ score of serial killers falls within the normal IQ range, contrary to mainstream portrayals of serial killers often possessing unusually high IQs.
Please note that the large standard deviation observed within this dataset likely stems from reporting biases of unusually high or low offender IQ scores due to public sensationalization of murder trials. The “average” serial killer’s IQ is underreported and publicly underrepresented in known data sources.
IQ Differences Among Serial Killers
Based on existing data on serial killer IQ scores, Radford researchers identified several notable findings. Generally, the greater the number of serial homicides committed by the offender, the higher their IQ. Female and male serial killers were found to have similar IQ scores. After the age of 20, the older the offenders were when they committed their first kill in a series, the higher their IQ was found to be.
Hedonistic serial killers who were primarily motivated by financial gain presented with the lowest IQ scores of the dataset (87.2), whereas hedonistic serial killers motivated by enjoyment (no element of rape present) presented with the highest average IQ scores (105.7). Additionally, the highest average IQ scores were those of White serial killers (IQ score of 101.3), followed by Asian serial killers (IQ score of 95.5), with the lowest average IQ scores observed in Black serial killers (IQ score of 79.1). Killers with higher IQ scores tended to strangle their victims, whereas offenders with lower IQ scores tended to bludgeon their victims.
The racial differences in IQ scores are likely tied to socioeconomic and environmental factors known to affect IQ. According to Ethnic differences in children's intelligence test scores: role of economic deprivation, home environment, and maternal characteristics, adjusting for these factors eliminated racial IQ differences within the general population.
Education Levels of Serial Killers in the United States (Historically–2020)
Of the 1,398-offender sample on which Radford and FGCU researchers compiled education data, 58.9 percent of serial killers did not graduate from high school. At the time of their first killing, the highest education level of offenders was as follows: 26.9 percent held a high school diploma, 3.2 percent had a GED, and 0.9 percent had a nursing degree (RN, LPN). Further, 1.2 percent held an associate degree, 5.4 percent held a bachelor's degree, 1.4 percent had a master's degree, and 3.5 percent possessed a doctorate.
How Differences in Serial Killing Methods Statistically Differ by Race and Ethnicity (United States, Historically-2023)
Black serial killers were found to be more likely to shoot their victims than White serial killers, while White serial killers used poison more often than their Black counterparts. White serial killers were more likely to mutilate their victims’ bodies after death and to engage in torture than Black serial killers.
Instances of necrophilia, cannibalism, and blood consumption, while relatively rare, are activities more often found in White serial killers than Black serial killers. Black serial killers were, on average, the youngest at the time of their first kill (25.5 years old), followed by Hispanic killers (27.5 years old), White killers (29.3 years old), and Asian serial killers (31.2 years old).
| Killing Methods Used By Black and White Serial Killers - Overall Percentage(United States, Historically–2023) | ||
|---|---|---|
| Killing Method | White Offenders | Black Offenders |
| Shoot | 26.1 Percent | 49.7 Percent |
| Strangle | 14.3 Percent | 12.4 Percent |
| Stab | 12.1 Percent | 7.6 Percent |
| Poison | 10.9 Percent | 0.4 Percent |
| Bludgeon | 7.9 Percent | 4.5 Percent |
| Stab/Shoot | 6.8 Percent | 9.4 Percent |
| Bludgeon/Stab | 5.3 Percent | 2.6 Percent |
| Strangle/Stab | 5.2 Percent | 3.3 Percent |
| Bludgeon/Shoot | 4.1 Percent | 4.3 Percent |
| Strangle/Bludgeon | 3.9 Percent | 3.5 Percent |
| Strangle/Shoot | 3.1 Percent | 2.4 Percent |
| Bomb | 0.4 Percent | 0.0 Percent |
Serial Killer Childhoods: Abuse and Early Behavioral Patterns (United States, Historically)
An average of 73.2 percent of serial killers reported abuse in their childhoods. Of these, physical abuse was most commonly (48.9 percent), followed by psychological abuse (48.7 percent), and sexual abuse, reported in 26.4 percent of these cases.
Compared to the general population in the United States, the 88 percent of serial killers raised by one or both birth parents was similar to the 87 percent observed in non-serial killers. Also, compared to the U.S. population in general, serial killers were “less likely to be only children” and “more likely to be middle-born children”.
Conclusion – Understanding Serial Killer Methodologies Through Data and Psychology
Patterns in serial killer methodology demonstrate how environmental and social influences may converge to shape the serial killer’s modus operandi. Identifying the interplay between an offender’s personal characteristics and their chosen methods of killing provides criminal justice practitioners with valuable insights into the situational, psychological, and social factors that drive serial homicide. To effectively confront the darkest corners of criminal behavior, we must gain insight into the madness from a place of curiosity, rather than one based on fear.