This misconception, the psychologists warn, is a "deadly mistake". They point out that one in six serial killers are female. Their crimes tend to go undetected for longer than their male counterparts, likely in part because "our culture is in denial of women's proclivity for aggression."
Harrison and her team have profiled 64 US female serial killers active between the years 1821 to 2008. The researchers used the murderpedia.org website to identify these killers and they verified the cases they found using reputable news sources.
The female serial killers had murdered between them at least 331 victims (making an average of 6 victims each). Their victims are of both sexes, but disproportionately male. The women had an average age of 32 at the time of their first killing, and poisoning was the most common method. However, between them, the women used a range of murderous techniques, as the researchers explained:
"Contrary to preconceived notions about women being incapable of these extreme crimes, the women in our study poisoned, smothered, burned, choked, shot, bludgeoned, and shot newborns, children, elderly, and ill people as well as healthy adults; most often those who knew and likely trusted them."Many of the homicidal women had stereotypically female professions, including being nurses and baby-sitters. They tended to be above average in physical attractiveness, which may have helped to engender trust in their victims.
As to motives, the most common was "hedonistic", a category in forensic psychology that refers to killing for financial gain, lust or thrill, with nearly half the sample fitting this category. The next most common motive was "power-seeking", which includes killing people in one's care.
The researchers urge caution regarding the factors that contributed to these women becoming serial killers. Apart from anything else, the historical records are incomplete and the absence of information does not mean that a given factor was not contributory. Nonetheless, Harrison and her team highlight several noticeable patterns in the data: a greater proportion of the women, as compared with the general population, had: a history of having been physically or sexually abused; drug or alcohol problems; and a diagnosis or signs of mental illness.
Quotes from some of the killers hint at their psychopathological thinking:
"They [the children] bothered me, so I decided to kill them."A striking contrast with male serial killers is the relative absence of sexual violence and deviance. Two exceptions were a female serial killer who was a rapist, and another who reportedly barked like a dog during sex. But overall, the researchers highlighted how the women in their study primarily killed for resources, while their male counterparts kill for sex. This follows evolutionary theory, Harrison and her co-authors explained, in the sense that men are said to be motivated more by seeking multiple sexual opportunities, while women are motivated to find a committed partner with sufficient resources. "However," they added, "although an evolutionary framework can offer understanding, we stress that these heinous acts are a vicious extension of unconscious drives and are not therefore 'normal' or 'excused' ... ".
"I like to attend funerals. I'm happy when someone is dying."
"That is my ambition, to have killed more people – more helpless people – than any man or woman who has ever lived."
The new analysis points to a worrying trend: a 150 per cent increase in the number of reported cases of female serial killers since 1975. This study has obvious limitations, most obviously the reliance on historical records and news reports, and its exclusive focus on US killers. However, it makes a valuable contribution to a neglected topic.
The researchers concluded: "Increasing our understanding of serial killers may minimise the number of victims potentially lost in the future while maximising the effectiveness of interventions to prevent vulnerable individuals from taking a killing path."
Harrison, M., Murphy, E., Ho, L., Bowers, T., & Flaherty, C. (2015). Female serial killers in the United States: means, motives, and makings The Journal of Forensic Psychiatry & Psychology, 1-24 DOI: 10.1080/14789949.2015.1007516
Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.