10 Misconceptions About Serial Killers

Serial killers are thought to be exceptionally intelligent. But how smart do you really need to be to get away with murder?
On the hunt for serial killers.
On the hunt for serial killers. / Jeremy Hogan/Photodisc/Getty Images
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If you’re obsessed with true crime but want to know the real facts about serial killers, we’re setting the record straight on certain stereotypes associated with this horrifying category. From whether they’re really more intelligent than the average person, to if they’re truly loners, to the facts about criminal profiling as seen in shows like Mindhunter, we’ll reveal the truth in a list adapted from an episode of Misconceptions on YouTube.

1. Misconception: All serial killers are incredibly smart.

The media often portrays serial killers as evil geniuses, tricking their victims and evading law enforcement for years, all without arousing suspicion from the people around them. But how smart do you really need to be to get away with murder? Is the IQ of the average serial killer really higher than that of the rest of the population?

IQ tests administered in serial murder cases have found that the perpetrators of these crimes aren’t any smarter than the general population. The average serial killer IQ falls around 95, while anything between 90 and 110 is considered typical. Murderers who are able to cover up their crimes are usually driven by an obsessive nature, but that isn’t necessarily a marker of intelligence. This myth about superior intelligence may have contributed to the idea that serial killers only get caught “because they want to.” But that’s probably not quite right, either. According to the FBI’s website, “As serial killers continue to offend without being captured, they can become empowered, feeling they will never be identified. As the series continues, the killers may begin to take shortcuts when committing their crimes. This often causes the killers to take more chances, leading to identification by law enforcement. It is not that serial killers want to get caught; they feel that they can’t get caught.”

Certain kinds of serial killers tend to be smarter than others. According to one analysis, murderers who used explosives had an average IQ of 140, which is considered superior intelligence. Perpetrators who used the more direct approach of bludgeoning came out below the national average at 79 points. 

2. Misconception: All serial killers have dozens of victims.

When you hear the term serial killer, you likely think of a long Wikipedia page and a victim count in the double digits. But while murderers who check those boxes get the most attention, they’re far from typical. According the FBI’s definition, criminals need to kill a minimum of two people to be considered serial murderers. It doesn’t matter if the victims were unlucky hitchhikers or rival gang members—the killings just need to be two separate incidents, and there has to be a “cooling off” period between them. By this definition, there are a lot more serial killers out there than people may assume—they’re just not prolific or idiosyncratic enough to warrant a creepy nickname or their own Netflix series. 

3. Misconception: All serial killers are mentally ill.

When the general public hears about a person who commits multiple murders, they’re apt to say the culprit is mentally disturbed. That may be true in the colloquial sense, but it isn’t the same thing as legally being declared clinically insane. And it risks painting people who suffer from mental illness with an unfair and misleading brush. 

There are a few different tests for the insanity defense to hold up in court, but the most famous is if the defendant is determined to have been mentally incapable of understanding the gravity of their actions when committing the crime. Under this strict definition, very few murderers qualify as legally insane. When serial killers do have mental disorders, they rarely suffer from the psychotic conditions that pop culture conflates with violent behavior, such as schizophrenia. As Scientific American explains, “Serial killers are much more likely to exhibit antisocial personality disorders such as sociopathy or psychopathy, which are not considered to be mental illnesses by the American Psychiatric Association.” People with these conditions may exhibit a lack of empathy or remorse, but they’re still intellectually capable of distinguishing right from wrong. These disorders can also be difficult for outside observers to spot, as many people with personality-related disorders are high-functioning and adept at performing socially accepted behaviors. 

And, of course, not everyone diagnosed with serious mental illness commits violent crime. Studies have found that patients with severe mental illnesses only show significantly higher rates of violence in connection to substance abuse. This suggests that the comorbidity of drugs and alcohol with mental illness is a better predictor of violent crime than the conditions alone. A fact that you may not have heard is that people with schizophrenia are much more likely to fall victim to violence than the general population, and the stigma around this disorder may contribute to that troubling trend.

4. Misconception: Serial killers can’t stop killing.

The act of serial killing is often portrayed as an addiction in popular media. Once the perpetrator gets a taste for murder, you would think they were incapable of stopping. In reality, some serial killers have been known to quit their criminal habits. The FBI cites Dennis Rader, or the BTK killer, as an example. After killing 10 people between 1974 and 1991, he seems to have stopped. Rader was arrested in 2005, 14 years after his last murder. Sometimes a change in circumstances, like a move or a marriage, can interrupt a serial killer’s life of crime. In other instances, they’re able to find an outlet for potentially violent compulsions in consensual or solitary sexual activities. 

5. Misconception: Serial killers are only motivated by sex.

Mug shots of serial killer Jeffrey Dahmer.
Mug shots of serial killer Jeffrey Dahmer. / Ralf-Finn Hestoft/GettyImages

That brings us to our next misconception: All serial killers are driven by sexual urges. This idea comes from the fact that many of the most famous serial killers sexually abused their victims, including Albert Fish, Ted Bundy, and Jeffrey Dahmer. There is indeed a sexual component to many serial killings, but sex isn’t the only reason these crimes happen. Greed is another common motive. H.H. Holmes, the serial killer who operated in Chicago in the late 19th century, amassed wealth through his murders by taking out insurance policies on his victims and stealing their property.

Some killers seek excitement or an outlet for anger. This was likely a factor in the D.C. sniper killings of 2002, during which John Allen Muhammad and Lee Boyd Malvo shot 13 victims, killing 10 of them.

6. Misconception: All serial killers are loners.

It’s easy to see why serial killers are so often painted as social outcasts. If someone is capable of breaking a taboo as serious as murder, it’s hard to imagine them functioning as a normal member of society. But many serial killers lead apparently normal lives before they’re apprehended—apparent being the key word. The FBI writes in its report on serial murder that “the majority of serial killers are not reclusive, social misfits who live alone.” Many of them have families, neighbors, and coworkers who would never suspect them of violence. The ability of many serial killers to lead apparently normal lives sometimes explains how they’re able to get away with their crimes long enough to kill multiple times. 

When it comes to their criminal activity, most repeat murderers do like to fly solo. But not every serial killer is a lone wolf by definition. Approximately 10 percent of these offenders kill in groups of two people or more. So even when the well-adjusted façade is down, a significant number of killers prefer collaboration over isolation.

7. Misconception: Only men can be serial killers.

It’s true that serial murder is a male-dominated field—and one that most women presumably aren’t eager to break into. Nearly all of the most famous criminals in this category from the past century-and-a-half are men. But that doesn’t mean female serial killers are nonexistent, or even that rare. According to a 2015 report from experts at Florida State University and the California School of Forensic Studies, roughly 16 percent of America’s serial killers are women. According to Scientific American, women are responsible for about 10 percent of all murders. That means “women represent a larger percentage of serial murders than all other homicide cases in the U.S.”

Female serial killers are more likely to poison their victims. A greater proportion of them work in health care, where they kill by giving lethal overdoses to patients. And the women who commit serial murders more commonly work as part of a pair or team, unlike the “lone wolf” killers the media likes to endlessly discuss and, at times, even glorify.

8. Misconception: Criminal profiling is an effective way to identify serial killers.

There’s an entire genre of crime television that relies on the misconception that criminal profiling works. In such shows, investigators are able to determine personal details about a serial killer—from their age to their relationship with their parents—just by analyzing a murder scene. This process makes for good TV, but it may be a waste of time in real life. 

According to a 2007 meta-analysis published in the journal Criminal Justice and Behavior, criminal profilers are just marginally better at guessing “offender characteristics” than non-professionals. Even when profilers do come up with accurate predictions, it doesn’t tend to make much of an impact on the case. Criminal profiling rarely, if ever, provides a direct lead to a wanted killer. Between its vague nature and the lack of research supporting its validity, criminal profiling has been criticized as a reckless misuse of police time and resources. That doesn’t mean you can’t still enjoy Mindhunter, but you may have to work a little harder to suspend your disbelief. 

9. Misconception: A serial killer’s M.O. never changes. 

When dealing with serial murder, investigators pay close attention to the killer’s M.O., or modus operandi. In criminology, an M.O. describes the method an offender uses to commit their crimes. Identifying the M.O. can be useful in solving multiple murders committed by the same person, but it would be a mistake to assume a killer’s M.O. never changes. According to FBI agent and behavioral analyst John Douglas, a serial murderer’s M.O. should be viewed as a work-in-progress that evolves the longer he’s active. He told Mental Floss in 2019, “when a criminal starts perpetrating crimes, if something doesn’t go right, he’s got to perfect the M.O.”

It’s also a mistake to use M.O. and signature interchangeably. While an M.O. refers specifically to the murder method, a killer’s signature is a ritual that isn’t necessary to commit the crime. If a serial killer collects the same garment from each of their victims as a trophy, that does nothing to aid them in their crime—in fact, it could make them easier to catch. M.O. and signature are both important pieces of information in serial killer cases, and understanding how they work and differ is vital to the investigators’ success.

10. Misconception: Serial killers pose a serious threat to the average person.

Consume enough true crime content and you’ll start to suspect that serial killers are lurking around every corner. The truth is that serial killers pose a much smaller threat to the average person than our culture’s obsession with them would have you believe. According to the FBI, serial killers are responsible for less than 1 percent of all murders in the U.S. Just 30 people fell victim to serial murderers in 2015. The reality is that the 24,576 homicide victims who were murdered in the U.S. in 2020, for example, were much more likely to be targeted by someone they knew than a random person who was out for blood—but those cases don’t always make for exciting podcast fodder.