The differences between male and female serial killers

In what's set to be something of a groundbreaking new documentary series, some of the world's foremost forensic psychologists and psychiatrists share their insights into the unique psychologies of some of history's most notorious murderers. The series, exclusive to Crime+Investigation, is called Making a Monster and it delves deep into just what creates the uniquely barbaric mindset of a serial killer. 

Aileen Wuornos

Among those profiled are two of history's most infamous and reviled female serial killers, Aileen Wuornos and Rosemary West. As viewers will discover, there are often quite noticeable differences in the way that male and female serial killers operate. 

Let’s investigate some of the biggest contrasts, shall we? We’ll do so by focusing on the psychological elements specifically…

Motive

Perhaps the biggest contrast between the two sexes when it comes to repeat murderers is motivation. 

The single biggest driver for male serial killers is sexual compulsion. That’s not to say that all male serial murderers rape their victims, far from it. But on some level there is generally a sexual element, even if it’s purely psychological. Male multiple murderers are often compelled to kill. An innate urge drives them to take the lives of others. Often - profile aside - the identity of the victim isn’t even that important.

Compare that to female serial killers and we see a polar opposite. When a woman kills, there’s usually ‘a reason’. There’s pragmatism and justification (at least in the killer’s mind, anyway).

The reason behind the killings may be money or convenience. It could be to benefit from a will, for instance. Often, it’s to get a male spouse or partner out of the way - again, for either money or convenience. Or the motive might well be revenge; an act of violence as catharsis. 

Sometimes, a woman will kill a close family member (such as a child) in order to garner sympathy and attention from friends, family and the wider community. This is not a motive often seen amongst male killers. In fact, it’s exceptionally rare.

Modus Operandi

Let’s get down to the brass tacks of the thing… the murdering part. In this context, it’s where the most fundamental and obvious differences between the sexes exist. On the whole, women serial killers are far more low key than their male counterparts.

Studies looking at the MO of women that kill have found that they’re much more likely to kill by poisoning, drowning or suffocating. Whereas men are happier using brute force and more violent means such as shooting, stabbing, strangling, bludgeoning or beating to death. 

A suggested reason behind this could be practicality. Strangling someone or bashing their brain in takes a test of strength - an area where men generally have an advantage. But from a psychological viewpoint, it could be seen as though women killers are more inclined towards subtlety and cunning. Often, the more violent a murder, the more evidence is created and the greater the chance of getting caught.

Male killers are nearly six times as likely to kill a stranger.

Research into the differences between the sexes in serial killing has found that male killers are nearly six times as likely to kill a stranger, whereas female serial killers are almost twice as likely to kill a person that they’re already familiar with.

On top of that, some 65.4% of male serial killers - to one degree or another - stalked their victims before murdering them, compared to just 3.6% of female serial killers.

Deadly Duos

The archetype of the serial killer is generally thought of as a lone wolf. For the most part, that’s true. But serial killing partnerships are not as rare as you may imagine. True, the most famous duos are men (Henry Lee Lucas & Otis Toole, The Hillside Stranglers, Leonard Lake And Charles Ng...), but mixed sex serial killing couples aren’t unheard of.

When a man and woman embark on a killing spree together, as with any partnership, there will usually be a dominant and a submissive. To varying degrees. When the killers are male and female, the man will generally be the dominant driving force behind the crimes.

A useful example of this phenomenon comes in the shape of Gerald and Charlene Gallego. Between 1978 and 1980, the married couple kidnapped, raped and killed ten young women. ‘The Love Slave Killers’ would keep the women as sex slaves before murdering them. It was clear to police that, as with almost all other depraved joint ventures of this kind, that the man was the one in control.

After thirteen years in jail, Charlene was eventually released. In an interview she gave while a free woman she summarised the two year death spree like this: "There were victims who died, and there were victims who lived. It's taken me a hell of a long time to realize that I'm one of the ones who lived.

An Evolutionary Explanation

What’s behind this different approach? One very interesting theory suggests that evolution may be behind it.

Associate professor of psychology at Penn State Harrisburg Marissa Harrison has carried out extensive research into the area and believes that gender-specific roles throughout history may well inform behaviour now. Essentially, the idea is that tens of thousands of years of gender roles have imprinted onto our brains.

The different approach could be down to something as basic as the notions of men traditionally being ‘hunters’ and women ‘gatherers’. The data seems to back that idea up. As we’ve mentioned, the research shows that male serial killers are far more inclined to kill strangers, while female serial killers generally murder those they know. 

'Historically, men hunted animals as prey and women gathered nearby resources, like grains and plants, for food,' says Harrison in her paper on the subject. 'As an evolutionary psychologist, I wonder if something left over from these old roles could be affecting how male and female serial killers choose their victims.'

'Evolution doesn't mean you're predetermined to do certain things or act a certain way. It means that it may be possible to make predictions about behavior based on our evolutionary past. In this case, I do believe that these behaviors are reminiscent of sex-specific behaviors or assignments in the ancestral environment. And perhaps we can understand this better through an evolutionary lens.'

The Exceptions That Prove the Rule

Having read this article to this point you may well be thinking, ‘interesting… that kinda makes sense. But this doesn’t sound like how Rose West or Aileen Wuornos operated.’ And you’d be right.

The fact is, female serial killers that behave to type (which is generally most of them) aren’t quite as ‘interesting’ to everyone. After all - which stands out to you? The woman cruising the freeways and highways of America, blasting holes through seven mens’ heads? Or the woman that poisons her husband's casserole in order to benefit from their wills? 

It’s the very fact that two women could attack, brutalise, torture and kill in the ways that West and Wuornos did that makes them so endlessly fascinating and worthy of attention and study. They are, effectively, exceptions that prove the rule.

Wuornos killed outside the home, out of anger and with violence. West stalked and lured women before sexually assaulting and killing them. Both killed ‘like men’.

Male and female serial killers may - for the most part - act differently from one another, but there’s one thing that’s certain... Regardless of sex, or any other differentiating factor, monsters are made. And learning how they’re made is hugely compelling.