Sexual Serial Killers

Infamous Sexual
Serial Killers
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Ted Bundy, a sadistic
sociopath serial killer[24]

Serial killing is defined by the FBI as the act of committing at least three killings on separate occasions over a certain period of time.[9] This heinous crime is committed with varying aspects and elements, from the type of targets a killer pursues to the manner in which the actual crime is committed. As such, serial killing is not a crime that is consistent and continuous in all aspects; instead it is accompanied with different characteristics including those that involve some sexual activity. Much research has been done as an attempt to demystify this incomprehensible behavior. However, it is clear that unlike the mechanics of memory, killing behaviors cannot be analyzed using an fMRI as the act is being committed. Accordingly, most research has been aimed instead at analyzing the traces that these sexual serial killers leave behind in crime scenes.[33] Because of this, there have been different classifications suggested to categorize sexual serial killers. Research has found the presence of psychopathy, neurological impairments, and sadism in these kinds of criminals.[33] Once captured, these criminals can be interviewed and scanned for brain abnormalities for further examination.

1 Development of a Sexual Serial Killer

1.1 Associated Brain Abnormalities

Brain Abnormality
as a Predisposition, not a Cause
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Neuroscientist Jim Fallon's PET scan
on right resembling those
found in murderers[42]

Although there are no specific researches focusing on brain abnormalities in sexual serial killers, there have been researches aimed at brain function abnormalities related to sexual behaviour (see sex and the brain) and also at violent and lethally aggressive behavior. It is important to note that the findings seen in these fMRI brain scans do not guarantee the individual showing antisocial and/or psychopathic behavior, instead abnormalities in these regions lead to a predisposition to these types of behaviors. In fact, not all following findings are consistent in all sexual serial killers, with some showing no pathological cause, and those with defects showing varying degrees of severity.[38] The frontal and temporal lobes have been seen to have involvement in sexual behavior, while only the frontal lobe has been implicated in violent, aggressive behaviour.[6]

1.1.1 Sexual Behaviour

Many researches and studies have demonstrated the roles of the frontal and temporal lobes in sexual behaviour, especially in many animal studies and only recently, in human studies due to the initial lack of research in human sexual behavior.[6] In animal studies, it has been shown that interfering with the temporal lobe and its structures can either elicit or eliminate sexual behavior depending on the type of manipulation done.[9, 11, 36, 37] Increased sexual activity was observed following the stimulation of deep temporal lobe structures.[7, 22, 23, 37] In lesion studies, the amygdala and hippocampus were proven important in the act of copulation. [13, 14, 34] In addition, testosterone was of significant value to copulation as well.[14, 15, 21] An influential study by Kluver and Bucy in 1939 further implicated the importance of the temporal lobes in sexual activity, which lead to the discovery of a syndrome, named after the researchers, Kluver-Bucy syndrome. Following the removal of both temporal lobes, certain behaviors were observed in these animal models, including decreased anger and fear, an excessive tendency to pay attention to all stimuli, the necessity to put everything in their mouths, the lost ability to recognize objects and finally an increase in conspicuous sexual behaviour.[17] Together with these findings and another study, researches speculated that these overt sexual behaviors, which lead to the animal models mounting both animate and inanimate objects, accounted for an inability to recognize suitable sexual partners.[8] The medial portion of the temporal lobe was particularly accountable for these observed behaviors, both physiological and libidinous (sexual desire).[8]

PET Brain Scan
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Control on the top & murderer on the bottom 
showing reduced orbitofrontal cortex (ORB)
 and anterior temporal lobes (AT)[4]

The consequences of temporal lobe abnormalities were further recognized in human subjects that suffered from temporal lobe epilepsy.[8] Researchers observed hypo-sexuality, a loss of sexual interest along with decreased genital arousal, followed the seizures. Along with hypo-sexuality, other atypical sexual behaviors were observed including paraphilia, fetishism, transvestism, voyeurism, sadism, masochism, frotteurism and genital self-mutilation.[5] In fact, administration of drugs preventing these temporal lobe seizures restores normal sexual behavior, and subjects showed sexual desire and ability.[2, 3] Studies in temporal lobe epilepsy have implied excessive activation of temporal lobe and its structures lead to inhibitory effects while under-activation of the same structures exhibit excitatory effects.[6] Additionally, abnormalities in the right temporal horn were likely to be seen in sadists.[19]

As previously mentioned, the frontal lobe was found to be involved in abnormal sexual behavior.[6] More specifically, studies have pointed to the possibility of the frontal lobe’s involvement in developing personality, intelligence and verbal and overt behavior. In fact, studies have shown that damage to this region can induce behaviors of impulsivity, a lack of concern as well as a lack of inhibition, which are all attributes seen in many killers. [38] A study in 1985 demonstrated orbitofrontal region damage lead to changes in sexual behavior. [5] In a later study, damage to the same region (OFC) showed lowered moral and ethical standards, feelings of euphoria, coarse language, along with excessive and disinhibited sexual desires that lead to engaging in forceful sex with partners. Thus researches up to date have attributed the orbitofrontal lobe as having an important role in disinhibited, impulsive behavior, promiscuous sexual behavior and a general lack of understanding of social mannerisms. [2, 3]

1.1.2 Violent Behaviour

PET Brain Scan
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Normal control on the left & murderer on right showing low PFC activity[26]

Lethally violent and aggressive behaviors have often been associated with antisocial personality (see ASPD) and psychopathy. In fact, in a majority of sexual serial killers, antisocial behavior has often been demonstrated.[29] Deficits in many brain regions have been implicated in antisocial behavior, specifically the prefrontal lobe, temporal lobe, amygdala, the hippocampus, insula and the cingulate gyrus.[1, 16, 28] Out of these brain regions affected in antisocial personality, the prefrontal lobe has been proven to be the most damaged structurally and functionally. In a meta-analysis of studies that focused on antisocial, psychopathy and violent behavior, localized defects were seen in particular brain regions including the right orbitofrontal cortex, the left dorsolateral prefrontal cortex and the right anterior cingulate cortex. [29] In this analysis, findings pointed to the prominence of a right-sided prefrontal pathology, particularly in a study by Tranel where unilateral lesions in the right OFC caused dysfunctional social conduct, decision-making, emotional processing and personality. [35] Unilateral lesion in the left OFC, on the other hand, exhibited normal social behavior. Lesions in the right ACC were seen to have negatively affected inhibitory control and emotional processing along with impairments to higher cognitive and self-regulatory processes with left dorsolateral PFC lesions. [35]

Overall, lesion studies collectively have pointed to the fact that reduction in the right prefrontal region, particularly the orbitofrontal and anterior cingulate cortex, lead to deficits in emotional processing and decision-making. Lesions in the left dorsolateral prefrontal cortex, on the other hand, lead to defective behavior and impulsivity control seen in many antisocial individuals. In addition, criminal psychopaths tended to have a decreased activation in the right hemisphere, particularly in the temporal lobe along with the amygdala and the hippocampus. [27] Temporal lobe defects may predispose an individual to antisocial behavior such as deficient moral judgment and social obedience, while frontal lobe defects target mostly impulsivity, decision-making, and emotional processing. [40]

1.1.3 Case Study: Ted Bundy

"I've lived in prison for a long time now and I've met a lot of men
who were motivated to commit violence just like me. And without exception,
every one of them was deeply involved in pornography."

Ted Bundy, showcasing his ability to have lead a normal life,
fitting into society, providing minimal to no signs of his psychopathic,
sadistic nature. In his last few hours, Ted Bundy discusses his young life,
his path to sexual addiction and the development of his sexually lethal behaviour.

2 Sexual Homicide Classifications

2.1 Types of Crime Scenes

Investigators over the years have noticed distinguishing features in the crime scenes that sexual killers leave behind and have narrowed it down to two classifications: organized and disorganized crime scenes. [30] Using the prominent features found in these types of crime scenes, researchers have also been able to associate these features to possible characteristics of organized and disorganized sexual murderers.

2.1.1 Disorganized Crime Scenes

Disorganized crime scenes involve lack of planning as the name might already suggest. As such, weapons may be carelessly left at the scene. Other features may not be as apparent, such as positioning the dead body, performing sexual acts on the dead body, depersonalizing the body, and keeping the dead body. [30] Disorganized crime scenes also are likely to be committed without the use of a vehicle, which further emphasizes the lack of planning and impulsiveness of the crime. [30] These features are likely to be exhibited by sexual killers that come from an unstable home where they were possibly treated with hostility as a child. As well, they might be sexually inhibited or ignorant, have sexual aversions, which all may stem from the parents having sexual problems themselves. [30] At the time of the crime, the disorganized killer is more likely to be frightened and confused that causes leaving traces of evidence. The killer may also personally know the victim, live alone, and commit crimes near their place of work or home. [30]

2.1.2 Organized Crime Scenes

Murder Kit
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Ted Bundy's Murder Kit
found in his Volkswagen following
his first arrest by Salt Lake
City Police in 1975[31]

Organized crime scenes, on the other hand, exhibit some type of planning. An organized killer is more likely to demonstrate a desire to control the victim by the use of restraints perhaps.[30] Unlike the disorganized killer, the organized type would be more likely to commit sexual acts with the victim still alive. A vehicle is also more likely to be used.[30] As the features of the crime scene may already suggest, the organized killer would be more likely to be intelligent, knowing to plan the crime ahead of time. This type of killer would have the capability to hold a steady job, even being skilled in their profession; they are socially competent which would contribute to diminishing any suspicions about their character.[30] They may have sources of stress that have provoking effects, and thus at the time of the crime, they may be angry or depressed. These types of killers are structured, and careful about not getting caught and are more likely to follow crime events in the media.[30]

Although there are two distinguished types of crime scenes, they are not completely exclusive. For instance, a killer that exhibits the characteristics of the disorganized type may use a vehicle or restraints, features that are usually seen in organized killers.[33] The organized/disorganized typology has remained as one of the most influential models used to develop profiles of serial sexual killers during crime investigations.

2.2 Types of Sexual Killers

Another proposed and more recent model involves distinguishing between the sexual killers omitting dissection of the crime scenes altogether. Although crime scenes are not included in the discussion, this model realizes that sexual offenders are rarely specialists and acknowledges the variety of crimes they may commit along with sexual homicide. When sexual homicide is analyzed as part of the wide variety of antisocial behaviors killers may commit, three categories distinguish them as either competitively disadvantaged, psychopathic, or sadistic.[33]

2.2.1 Competitively Disadvantaged Killers

The competitively disadvantaged category focuses on one of the more heavily stated pathways to criminal behavior, neurodevelopmental insults. A study involving 10 killers were scanned for brain abnormalities and found temporal lobe irregularities in some sexual killers but absolutely none in non-sexual killers.[19] Along with a temporal lobe abnormality, sexual killers also showed elevated levels of testosterone.[19] The temporal lobe and testosterone levels, as previously mentioned, are important in sexual behavior. These developmental insults lead to cognitive deficits early in life, which may impede the individual’s abilities involved in problem solving, learning and memory.[33] Consequently these insults create the path for antisocial behavior. These defects are often seen to be associated with antisocial behaviors from their parents and impoverished neighborhoods, which further increases the likelihood of developing violent and aggressive behaviors.[12] All these insults collectively put these affected individuals at a disadvantage when competing with others for sexual partners, social status and resources.[33] These individuals may not have the mental capacity to decipher social sexual signals or lack thereof from the opposite sex. The inevitable antisocial behavior exhibited by these affected individuals eventually lead to a sexually coercive behavior, which develops initially by practicing short-term mating strategies that require only little investment in the many sexual partners they encounter.[18] This strategy proves to be inefficient in attaining willing partners, which may cause the frustrated individual to react with aggressive sexual behavior, to the point of committing sexual homicide.[33]

2.2.2 Psychopathic Killers

Psychopathy (see psychopathy) displays almost opposite characteristics to the competitively disadvantaged. In the psychopathic killer, there is no evidence of competitive disadvantage, in fact it has been shown that psychopathy is not pathological and is negatively associated with neurodevelopmental insults.[12] Instead, neurodevelopmental insults were found to only associate with violent behavior, as seen in the competitively disadvantaged.[12] Psychopaths are intelligent, exhibiting the ability to easily manipulate and take advantage of those around them. They are selfish, and unremorseful, giving no regard for others except for themselves.[33] As well, they display sexual promiscuity, impulsiveness and the constant need for extreme thrill and excitement.[33] The psychopathic killer's criminal career typically starts at a young age when sexual coercion and aggressive behavior emerges[32]As they age and enter adulthood, their criminal background is highly versatile stemming from their participation in methodical, goal-oriented crimes involving violence and aggression (see Ted Bundy).[33] Psychopathic sexual killers are likely to use a strategy of high mating effort, pursuing and aiming for a high number of sexual encounters, with little investment in each partner (as seen in the competitively disadvantaged). This strategy promotes sexual promiscuity and impulsiveness, which in turn satisfies their constant craving for extreme thrill and excitement. Interestingly, psychopaths have been found to focus on targets that are reproductively viable when compared to other types of sexual offenders.[12]

2.2.3 Sadistic Killers

Sadistic killers, unlike the competitively disadvantaged and the psychopathic, are less likely to have a life long criminal career.[33] They are able to hold a steady employment, have stable marital relationships and thus appear to have normal lives. However, they may exhibit antisocial behavior as well, mostly of the sexual nature. Sadistic killers will have constant, recurring fantasies about humiliating and torturing others. The physical and psychological suffering of others triggers arousal, accounting for their attraction to sexually aggressive behavior, particularly sadistic rape. These types of killers desire complete domination of their partner or victim, which forms an unhealthy strong connection between their sexual desire and the act of sex. Their desire for sadistic acts become overwhelming, which eventually leads as a motivation to kill[18], where they use excessive force and torture to satisfy as sexual stimulation.[25] As mentioned, they spend many hours fantasizing the sadistic act in crucial detail that when they actually commit the crime, they exhibit methodical and meticulous behavior that causes them to be attentive criminals.[33] As well, due to their fantasizing, they may keep some type of trophy or souvenir of the victim and the crime.[33]

2.3 Test of Two Typologies

Variables used in Sewall et Al.
analysis of 82 sexual serial killers[33]
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A recently published article by Lindsay Sewall, Daniel Krupp and Martin L. Lalumiere aimed to determine how efficient the disorganized/organized and the three-path (competitively disadvantaged/psychopathic/sadistic) models fare when used to classify real sexual homicide cases. They collected biographies of male serial sexual killers for their sample, using TruTV biographies, along with Wikipedia and the Encyclopedia of Serial Killers to support the information collected from TruTV, but with TruTV still taking precedence when information conflicted. To be included in the study, the researcher chose sexual homicide offenders that had demonstrated sexual activity before, during or after the death of at least one victim. They defined serial killing as the FBI had, as committing at least three homicides over a period of time. The sample of sexual serial killers was then coded on variable that related to the two different models, disorganized/organized model and the three-path model. A total of 33 variables were used shown on the right. The 33 variables were further reduced to the 5 following components: slashing, sadistic, instrumentality/ order, poor school performance, and anti-sociality. The analyses divided the offenders into 4 distinct clusters:

  • Cluster 1: high scores on sadistic and instrumentality/ ordered components
  • Cluster 2: high scores on antisocial personality disorder and poor school performance
  • Cluster 3: high scores on slashing and low scores on instrumentality/ order and anti-sociality
  • Cluster 4: average scores on instrumentality/ order and anti-social personality disorder & low scores on the remaining components.

The researchers found the results to completely support neither typology, showing varied support for each. Thus, they encourage future research to focus testing other models of classifying sexual homicide but also prepare for the possibility that any typology will prove to be insufficient in classifying sexual homicide due to heterogeneity found in these crimes. [33]

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Written by Karen Abogadil from the University of Toronto, HMB300H1 S 2013

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