Why There Are Fewer Female Serial Killers Than Males in the U.S.

Americans have long been obsessed with serial killers. From televised trials and true-crime podcasts to feature films and documentaries, the public fascination with the darkest side of humanity shows no sign of ebbing.

But while much of the media fascination has focused on male serial killers like Ted Bundy, Jeffrey Dahmer and John Wayne Gacy, female serial killers should not be underestimated. They may be less common in the United States than their male counterparts, but they can be just as lethal. And because they often use methods that are harder to detect, they can be tougher to catch.

Peter Vronsky, a filmmaker and crime historian who wrote Female Serial Killers: How and Why Women Become Monsters, tells A&E Crime + Investigation, “We are slow to recognize the prevalence of female serial killers because we are still saddled with old societal tropes, in which females are seen as passive and nurturing mother figures and primarily as victims when it comes to serial murder.”

Jana Monroe, who became one of the first female agents with the FBI’s Behavioral Science Unit in the 1980s, credits the fact that female serial killers are significantly rarer than males to “a complex interplay of psychological, biological and sociological factors.”

“Men tend to express aggression outwardly, while women are more likely to internalize aggression, leading to self-harm, depression, or relational manipulation rather than physical violence,” Monroe, whose work as a serial profiler inspired the Clarice Sterling character portrayed in The Silence of the Lambs, tells A&E Crime + Investigation. “Testosterone plays a major role in aggression, dominance behavior and risk taking. Estrogen and oxytocin, by contrast, are associated with bonding, empathy and caretaking behaviors, which act as protective factors against extreme violence.”

The subtle ways in which women kill can make it harder for investigators to recognize a female serial killer may be at work. According to Penn State psychologist Marissa Harrison, author of Justice Deadly: Psychology of Female Serial Killers, “Men kill overtly; they leave more brutal evidence behind. Female serial killers kill covertly and use means that are not as readily detectible. Police won't likely know it's homicide until they string together a series of deaths that are statistically unlikely—a hospital setting, numerous dead spouses, many dead children.”

The FBI considers serial murder to be the killing of three or more people, with a cooling-off period of at least a week between killings. However, the FBI did not even recognize the existence of female serial killers until the 1990s, and as recently as 1998, one (male) profiler claimed they didn’t exist at all. As of 2023, it was estimated that 8% of all reported serial murders in the U.S. are committed by women.

Harrison’s research has found that a female serial killer is likely to be white, in her 20s or 30s, middle class, of average intelligence and of average or above-average attractiveness. She may have been physically or sexually abused when younger, had traumatic issues with her parents and have a history of mental health issues. She’s likely to kill in a suburban area.

“Male serial killers are often driven by sexual or domination-based fantasies,” observes Monroe, “whereas female killers tend to kill for practical reasons: financial gain, revenge or perceived mercy.” The latter group, who often work in the caregiving industry, are often labeled as “angels of death.”

Additionally, says Harrison, “Men are much more likely to kill strangers; women are more likely to kill people they know or who are related.”

In fact, researchers found that male serial killers were nearly six times as likely to kill someone they didn't know, while female serial killers were approximately twice as inclined to murder a person they already knew. Male and female serial killers approaches also differ: 65.4% of male serial killers stalked their victims, while only 3.6% of female ones did.

Harrison believes the contrasting approaches of male and female serial killers can be traced back to ancestral times, when men would hunt animals as prey, while women stayed close to home and gathered nearby resources. “Male serial killers are hunters,” she says. “They stalk, they keep trophies from their kills, while female serial killers gather their victims around them.”

Unlike men, who often kill up close and personal, women are more strategic and cunning, often using sex and manipulation to lure their victims.

“Female serial killers are called ‘quiet’ because they don’t attract public and media attention the way male serial murderers often do,” Vronsky offers. “They don’t leave bodies of their victims by the roadside or send taunting notes to police or the media.”

Women also favor harder-to-detect methods such as poison or asphyxiation, which can further disguise their crimes. “Often authorities don’t even realize a murder has occurred because female perpetrators sometimes are employed in environments where people die a ‘natural death,’ like in hospitals or old age care homes,” Vronsky states.

In fact, Harrison notes that almost 40% of female serial killers works as nurses or health care professionals. “They use that as a cover to harm people, because nobody expects that someone who took a life oath to heal people would kill them,” he adds.

In the case of nurses who kill, power, not profit, tends to be the motive. “If a woman had an exceptionally adverse childhood experience, she may be seeking to regain some of the power she feels she lost,” Harrison observes.

Aileen Wuornos, dubbed the "Queen of the Serial Killers," was just such a woman: she craved revenge and power. A prostitute who worked the Florida highways, she was executed in 2002 after being convicted of the murder of seven men who’d paid her for sex. She was abused from an early age and grew up with a hatred of men.

“The No. 1 reason men and women kill is for control,” Monroe says, “and Aileen was exhibiting control over her victims.”

Wuornos has often been described as America’s first female serial killer, likely because of her fame and notoriety. More to the point, Wuornos was an outlier. There was nothing subtle about her methodology; her crimes mirrored the patterns of a male serial killer. Going forward, Monroe hopes that investigators develop more advanced methods of recognizing female serial killers. By doing so, they might turn out to be more prevalent than first thought.

“Historically, profiling and investigative frameworks have been written from a male perspective,” she says. “The offender is assumed to be male. Investigators must actively challenge that cognitive bias by asking, ‘Could a woman have committed this crime?’ early in the case and not as an afterthought.”

Monroe suggests incorporating behavioral analysts, medical examiners and forensic psychologists early in suspicious death reviews to surface patterns missed by “purely traditional, evidence-based policing.”

“To truly give credence to the possibility of a female serial killer,” she concludes, “they must look at the quiet manipulator, the person hiding in plain sight, whose methods are less cinematic but equally lethal.”