Modern Wisdom1 In 6 Serial Killers Are Women, Here's Why - Dr Marissa Harrison
CHAPTERS
- 0:00 – 1:31
Why female serial killers are overlooked (and how they differ from men)
Chris and Dr. Marissa Harrison open by challenging the default “serial killer = male sexual predator” stereotype. Harrison explains that female serial killers tend to be less sensational, often using methods like poisoning and pursuing motives such as money and power rather than sex.
- •Public schema of serial killers is dominated by infamous male examples (Bundy, Kemper)
- •Female serial killers often operate "low-key" and are therefore harder to notice
- •Common sex differences: women more likely poison; men more likely sexual violence
- •Motives differ: women more often money/power; men more often sex
- •Under-detection is partly driven by cultural assumptions about women as caregivers
- 1:31 – 2:39
“Grandma wouldn’t do that”: stereotypes that help women hide in plain sight
Harrison illustrates how caregiver stereotypes can prevent suspicion, using the “Giggling Granny” case to show the mismatch between appearance and behavior. The chapter frames why detection and attribution are slower when the offender fits a nurturing archetype.
- •Caregiver stereotypes reduce suspicion and delay investigation
- •Example: Nannie Doss (“Giggling Granny”) contradicts the "grandma" schema
- •Female offenders can resemble trusted community figures
- •Biases affect both reporting and law enforcement suspicion
- •Theme introduced: female serial killers often conceal wrongdoing behind normalcy
- 2:39 – 6:48
Backlash and criticism: the Lucy Letby case and public denial
Harrison describes the hostile responses she received after commenting on Lucy Letby, including ad hominem attacks and conspiratorial accusations. She emphasizes her evidence-based approach (court records, academic data) and wonders whether a male researcher would face the same reaction.
- •Lucy Letby used as a modern reference point for female serial murder
- •Criticism includes personal insults, accent mockery, and conspiracy claims
- •Harrison grounds her stance in trial evidence and established offender patterns
- •People double down when beliefs are challenged (motivated reasoning)
- •Open question: gendered reception of expert commentary
- 6:48 – 11:41
Why society is obsessed with serial killers—and the ethical line in true crime
From an evolutionary perspective, Harrison links morbid curiosity to protective vigilance: humans attend to threats to learn how to avoid them. The conversation then shifts to ethics—how true crime can become exploitative when it glamorizes violence and disregards victims and families.
- •Morbid curiosity as an evolved attentional bias toward threat
- •Interest is often unconscious (not literal self-protection planning)
- •True crime can blur fact and fiction through dramatization
- •Critique of treating murder as entertainment ("morbid museum")
- •Emphasis on empathy for victims and co-victims
- 11:41 – 13:32
How common are female serial killers? Prevalence estimates and rarity in practice
Harrison shares the headline estimate that roughly one in six U.S. serial killers are women, while stressing uncertainty and undercounting. She also notes how rare contemporary cases feel in practice—only a handful have crossed her radar in the last decade.
- •Estimated proportion: ~1 in 6 (U.S.), but true rate is uncertain
- •Serial murder itself is rare; female serial murder is rarer still
- •Recent examples discussed: Lucy Letby, Reta Mays, and others
- •Some cases never reach arrest/trial (including suicide pre-arrest)
- •Distinction between prevalence estimates and observed case frequency
- 13:32 – 16:42
Profile and demographics: what the data shows about female serial killers
Drawing from a 2015 study of 64 U.S. female serial killers, Harrison outlines common demographic and lifestyle patterns. The profile often contradicts pop-culture expectations: employed, suburban, sometimes married, frequently in caregiving roles, and often targeting vulnerable people.
- •Study basis: 64 U.S. female serial killers across U.S. history
- •Typical descriptors: white, middle class, suburban, Christian, employed
- •High caregiving-role prevalence, especially healthcare (nurses/aides)
- •Targets often vulnerable people under the offender’s care
- •Primary motive coding: money first, power second (with caveats about overlap)
- 16:42 – 19:33
Sex differences beyond stereotypes: education, mental illness, and “hunting vs gathering”
Chris and Harrison compare male vs female serial killers across education, victim familiarity, and mental illness rates—while noting measurement limitations across time. Harrison also introduces work on trophy-taking and discusses how different behavioral patterns can appear across sexes.
- •Men more likely target strangers; women more likely target familiar victims
- •Education: women often have some college; men more often under-educated
- •Mental illness: reported higher for men than women, but diagnostics vary historically
- •Trophy-keeping: more common in men, but women may also keep items (definition matters)
- •Substance abuse discussed as potentially downstream of deeper pathology rather than a driver
- 19:33 – 25:36
From nurturing to killing: caregiving instincts “gone awry” and nurse-offender puzzles
The conversation explores how someone in a caregiving identity (mother, nurse) could commit repeated killings. Harrison uses an evolutionary “bell curve” framing—most people cluster around normal caregiving, while extremes include neglect and violence—and notes uncertainty about whether the field attracts controlling personalities or changes them.
- •Caregiving is widespread, but traits vary across a distribution (bell curve)
- •Extreme tail: neglect/abuse can include filicide in rare cases
- •Nursing cases raise questions of control, access, and personality selection
- •“Angel of mercy” narratives often function as justification rather than truth
- •Strong caveat: the vast majority of caregivers never harm anyone
- 25:36 – 27:21
Marriage as cover and opportunity: why more female serial killers are married
Harrison explains how marriage can be instrumental—spouses may become victims, and repeated marriages can provide repeated access to insurance/inheritance. She returns to the broader theme that social normalcy (churchgoing, family life) can function as camouflage.
- •Marriage can supply both access to victims and financial payoff
- •Serial pattern can include multiple husbands (insurance/inheritance)
- •Historical example: Lydia Sherman (“Derby Poisoner”)
- •“Not who you’d suspect” reinforces delayed detection
- •Normal social roles can provide concealment and credibility
- 27:21 – 35:16
Does abuse create serial killers? Trauma, CSA, and altered threat reactivity
Harrison details frequent patterns of severe childhood abuse—especially childhood sexual abuse (CSA)—across both male and female serial killers, while emphasizing that most abused individuals do not become violent. Chris probes the implication: CSA may not dictate sexual motives, but may reshape aggression, threat perception, and nervous-system reactivity.
- •Higher-than-chance rates of physical/sexual/emotional abuse in histories
- •CSA described as a cross-sex common denominator in many cases
- •Neuroscience framing: trauma can recalibrate nervous system sensitivity
- •Important distinction: CSA is not destiny; base rates matter
- •Case illustration: John Wayne Gacy’s childhood narrative vs later crimes
- 35:16 – 38:56
Victim selection and detection: why women target the vulnerable (and how cases get missed)
Harrison explains that female serial killers often target those least able to resist—infants, elderly, disabled, or hospitalized people—because deaths can be attributed to natural causes. The chapter highlights a key investigative asymmetry: male serial killers often must be “caught,” while female serial killers often must be “detected” via anomaly recognition.
- •Female serial killers commonly have mixed-sex victims; men more often target women
- •Vulnerable victim groups: infants, elderly, ill, disabled, dependent persons
- •Deaths in hospitals/illness contexts can be explained away, reducing suspicion
- •Rare instances of female sexualized behavior discussed (e.g., Jane Toppan rumors)
- •Memorable framing: “catch” male offenders vs “detect” female offenders
- 38:56 – 44:31
Children as victims: serial filicide, Munchausen by proxy, and attention dynamics
The discussion quantifies child-only victim patterns as far more common among female serial killers than male. Harrison explains how serial definitions apply to repeated child killings over time and describes a prominent case (Mary Beth Tinning) where attention and medical-system fragmentation may have enabled repetition.
- •Child-only victims: far higher proportion in female serial killers (data shared)
- •Serial definition used: 3+ victims with a cooling-off period (often 1+ week)
- •Factitious disorder imposed on another (Munchausen by proxy) as a pathway
- •Case study: Mary Beth Tinning and suspected killing of multiple children
- •System factors: non-centralized records historically enabled pattern concealment
- 44:31 – 49:06
Motives through an evolutionary lens: sperm/eggs, resources, and hunter–gatherer patterns
Harrison links sex differences in motives to reproductive asymmetries and mate selection pressures: men’s higher average sex drive aligns with sexual motives, while women’s resource needs in ancestral environments align with financial motives. She also presents the hunter–gatherer hypothesis: men “hunt” strangers; women “gather” victims within their social orbit and gather profits.
- •Evolutionary framing: reproductive constraints differ for men vs women
- •Predicted motive alignment: men seek sex; women seek resources (money/power)
- •Hunter–gatherer hypothesis of serial murder (men hunt; women gather)
- •Behavioral correlates: stranger targeting, travel, trophy-keeping (men) vs familiar targets (women)
- •Acknowledgment of multi-factor causation beyond evolution (development, culture, history)
- 49:06 – 54:42
Weapons and methods: poisoning, pharmaceuticals, and caregiver access
Harrison details poisoning as the most common method and explains how toxins and medications can mimic natural causes (GI illness, heart attack). The conversation emphasizes opportunity: healthcare settings provide both access to lethal means and plausible cover for death.
- •Most common method: poisoning (including arsenic and other toxins)
- •Pharmaceutical poisoning: insulin or medication misuse to induce fatal events
- •Poisoning can mimic natural disease, complicating detection
- •Caregiver roles provide both access and plausible deniability
- •Healthcare knowledge increases ability to evade suspicion
- 54:42 – 1:00:55
Does modern society deter serial killers? Forensics, social media, and shrinking opportunity
Chris and Harrison discuss why classic serial-killer eras feel less common today: improved forensics, centralized records, and pervasive surveillance raise the odds of early detection. They also note that determined offenders may shift methods, but sustaining a serial pattern is harder in an interconnected world.
- •Modern toxicology/forensics can reveal poisoning quickly
- •Social media, cameras, and digital traces reduce anonymity
- •Serial criteria require repeated success; modern systems interrupt patterns earlier
- •Internet “crowd detectives” accelerate identification
- •Caveat: motivated offenders may still find alternative means (e.g., arson, stabbing)
- 1:00:55 – 1:02:58
Stopping crime upstream: why psychology and resources matter
Harrison closes by arguing that prevention requires both better-funded investigative capabilities and earlier psychological intervention for trauma. She frames many serial trajectories as potentially alterable with timely support—without minimizing accountability or victim harm.
- •Real investigations require funding; CSI-style speed is unrealistic
- •Need more resources for labs, testing, and detective work
- •Need more psychologists for early trauma intervention
- •Earlier intervention generally improves trauma outcomes
- •Goal: prevent escalation rather than only punish after the fact
- 1:02:58 – 1:03:32
Where to follow Dr. Marissa Harrison and her book
Chris wraps up by asking where listeners can find Harrison’s work. She points to her Penn State Harrisburg faculty page and her book "Just as Deadly: The Psychology of Female Serial Killers" (Cambridge University Press).
- •Penn State Harrisburg faculty webpage
- •Book: "Just as Deadly" (Cambridge University Press, 2023)
- •Paperback edition mentioned as upcoming
- •Available through major retailers
- •Episode outro and recommendations
