Female serial killers often times go under the radar. They’re a more unique breed, only representing about 16.7% of serial killers. But even more so, the image of a serial killer may be surprising when it comes to females.
“It’s going to be not who you think it is,” Marissa Harrison, a professor of psychology at Penn State University at Harrisburg, told Newsweek. “It’s probably a nurse, a grandmother, a mother, somebody you wouldn’t expect.”
Serial killer Lucy Letby, 34, was a former neonatal nurse in England who murdered seven infants and attempted to murder six others between June 2015 and June 2016. She was charged in 2020 with eight counts of murder and 10 counts of attempted murder.
Her methods, which were revealed during a 10-month trial, included injecting the infants with air or insulin, overfeeding them and physically abusing them with medical tools. On Aug. 21, 2023, Letby was sentenced to life imprisonment.
“Would you think that a trained skilled nurse would be capable of neglect let alone that this woman brutalized one of the babies so much in the abdomen that the pathologist testified that the injuries were tantamount so that the baby looks like they got hit by a truck,” Harrison said.
Many would call Letby’s case a “one-off,” and while serial murder in general is rare, Letby still fits this “typical” female serial profile.
Harrison, who wrote “Just as Deadly: The Psychology of Female Serial Killers,” said this unassuming aspect of female serial killers’ identities is oftentimes why they “can get away with it” for longer than male serial killers. In fact, 39% of female serial killers work in health-related positions just like Letby.
“It’s usually somebody you would never expect to hurt somebody else,” Harrison said. “Our idea of nurse is not killer, or our idea of mother is not killer. The other thing is somebody who harms others is not in our schema of women. People just don’t think that women can do this.”
An FBI investigator even once famously said there was no such thing as a female serial killer.
“That’s not true,” Harrison said.
Harrison and her team wrote the first paper that she is aware of that compares the demographics, motives, methods and mental health characteristics of male and female serial killers.
Female serial killers were typically white, educated, married and in a caregiving role. In all cases that Harrison studied, female serial killers targeted at least one victim who was a child, elderly or infirm – people who had “little chance of fighting back.”
Criminal psychologist Rachel Toles said before the 1900s, serial killers were about 50-50 female and male because women would killer their children, oftentimes due to the lack of birth control or abortion opportunities back then.
“It’s a genetic component,” Toles told Newsweek. We’re unfortunately so behind in our field though.”
Enzo Yaksic, who runs the Atypical Homicide Research Group, added that female serial killers are “undercounted and sidelined.”
“They have traditionally been ignored by researchers having been discounted as being too weak and fragile to commit multiple killings,” Yaksic told Newsweek. “But many female serial murderers have been able to hide behind the attributes of trustworthiness and kindness typically ascribed to them to become more efficient and methodical killers.”
Postpartum issues and a history of mental illness also play into this, like with Andrea Yates who confessed to drowning her five children in their bath in 2001. She exhibited severe postpartum depression, postpartum psychosis and schizophrenia. In 2006, a jury retrial found Yates not guilty by insanity.
“It’s rare, but it happens,” Harrison said. “The babies and the mother are in danger.”
Nearly 40% though have some form of a mental illness. This is not as drastic as data on male serial killers, but Harrison also believes there is missing data available.
“There is a large mental illness component here and for people saying there’s not they’re doing a huge disservice,” Harrison said. “We must pay attention to mental health in this country.”
Harrison urged everyday people to pay attention to those going through mental health crises or “raising red flags.”
“Don’t be afraid to ask questions,” Harrison said.
The female serial killer’s most common motive for killing was financial and power gain, according to Harrison. Yaksic also noted that there has been a significant increase in revenge-motivated murders among female serial killers over the past decade, representing 50% of cases.
One prime example is serial killer Aileen Wuornos, who was nicknamed “Damsel of Death.” Wuornos was convicted of murdering six men in Florida while engaging in sex work between 1989 and 1990. She would rob her male clients and shoot them dead. She claimed that her clients raped – or attempted to – her and that the homicides were in self-defense.
Wuornos originally traded sexual favors at her elementary school for cigarettes and other treats. She went on to become a sex worker. She was arrested in 1986 when one of her customers told police she had pulled a gun on him in the car and demanded money.
Wuornos was executed by lethal injection in 2002 at 46-years-old. The film “Monster,” starring Charlize Theron, highlights Wuornos’s first murder through her execution.
‘Traditionally difficult to apprehend’
Their most common method was poisoning.
Kristen Gilbert is a serial killer from Massachusetts who was convicted of four murders and two attempted murders of patients admitted to the Veterans Affairs Medical Center. She would induce cardiac arrest in her patients by injecting their intravenous therapy bags with lethal doses of epinephrine. She responded to the coded emergency, often resuscitating the patients herself. Prosecutors said she was on duty at the hospital for about half of the 350 deaths that occurred while she worked there.
The different methods, motives and targets also use to make female serial killers “traditionally difficult to apprehend,” Yaksic told Newsweek.
“Today, female serial murderers are far more likely to be apprehended due to a personal relationship with their victim,” Yaksic said. “71% of the 28 female serial murderers active between 2010 and 2024 were arrested after killing their own children, patients under their care, acquaintances, or romantic partners.”
For men, they are more likely to target women solely. They are also far more likely to commit sexual crimes and stalk their victims who are strangers, Harrison said. Dr. Robert Schug, forensic psychologist and criminology professor, told Newsweek the murders could be used for male serial killers to hide the sexual obsessions in a way. This is especially true for alleged serial killers like Rex Heuermann who focus on sex workers that are considered “lesser.”
In his book “Female Serial Killers: How and Why Women Become Monsters,” Peter Vronsky shows male and female serial killers have different “signatures.” He notes women often do not tend to sexually assault or physically mutilate their victims.
Toles said women don’t tend to live in this same “fantasy world” as male serial killers.
“Male serial killers are like hunters, so they stalk, and they keep records and pick out who they are going to kill,” Harrison said. “Women are gathering, gathering the people around them. They’re going to gather profits or power from their crimes.”
Uncommon Knowledge
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Newsweek is committed to challenging conventional wisdom and finding connections in the search for common ground.
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