Brain Abnormalities and the Sexual Murderer

Brain imaging.

Source: Alberto Bocchetta and others/Wikimedia Commons, Creative Commons Attribution 2.0

Brain abnormalities, as discussed here, encompass a manifold of fixed insults relating to functional and biochemical deviation, which may be resultant of genetic or environmental (e.g., sequelae of head injury or infection) origins (Elsevier; Holcomb & Dean, 2011). Anomalous brain functioning has been associated with aggressive and psychopathic (see Bannon et al., 2015; Weber et al., 2008; Aigner et al., 2000 for reviews) dispositions. Existing literature examining the brains of homicide offenders has yielded unsurprising findings. Raine and associates (1997), in their study of 41 murderers, found atypical functioning in brain areas, such as the prefrontal and anterior cingulate cortex. amygdala, thalamus, and medial temporal lobe. In a separate sample of 203 homicide offenders, researchers also highlighted the existence of aberrations in gray matter in the orbitofrontal and ventromedial prefrontal and temporal cortex regions (Sajous-Turner et al., 2020). Deficits or asymmetrical functioning in the above-mentioned areas have been associated with abnormalities in behavioural control, social cognition and appraisals, cognitive flexibility, and decision-making (see Sajous-Turner et al., 2020; Bush et al., 2000). Forensic neuropsychologist John Matthew Fabian, Ph.D., (2010) highlighted that studies of murderers have suggested a high prevalence of head injuries of this group and death-row inmates (all studies cited in Miller, 2002).

Existing research on sexual homicide offenders (SHOs; see Chan & Heide, 2009 for context) has suggested that these crimes are underpinned by both proximal (e.g., occupational, conjugal/relationship, problems) and life-course risk factors (e.g., early victimization, issues in the family system, cognitive distortions; Beauregard & Martineau, 2016; Gannon et al., 2009). Among these, brain abnormalities and head injuries are purported to be a potential neuropsychiatric vulnerability to this atypical form of offending. Wade C. Myers, MD (2001), in an exploratory study of the cases of sixteen juvenile SHOs, found that all offenders were afflicted with neuropsychiatric vulnerabilities. More specifically, these resulted from trauma, a lack of oxygen reaching brain tissues (i.e., anoxia), or infection. Moreover, one-quarter of the sample was determined to have been afflicted with seizures and abnormalities evidenced by electroencephalogram (EEG) findings. In a similar study authored by Myers and Blashfield (1997), it was determined that around half of juvenile offenders were afflicted with learning disabilities (57%), failed at least one school grade (54%), and had been enrolled in special education (46%) at some point in their lives prior to offending. However, the causal link between retrospective head injuries and anomalous brain functioning is not clear as it relates to the present sample.

The high prevalence of sustained head injuries and brain abnormalities among samples of SHOs has been highlighted in the literature examining developmental risk factors for adult sexual homicide offending. Häkkänen-Nyholm, Ph.D., and associates (2009) found in their study of a Finnish sample of SHOs that one of the seventeen offenders (5.9%) had been afflicted with an organic brain disorder (OBD). Interestingly, the researchers also highlighted a similarly high prevalence (10.6%) of OBD among non-sexual homicide offenders. Ron Langevin, Ph.D., and co-authors (1988, 2003, as cited in Beauregard & Martineau, 2016), further noted in a psychosexual examination of so-called “sex killers,” that SHOs underperformed on various neuropsychological test batteries, despite being of average intelligence. Utilizing the Halstead–Reitan and Luria Nebraska Neuropsychological Test Batteries, Langevin and associates noted that sexual murderers had failed both psychometric assessments at a rate of 20% and 17%, respectively. Moreover, around one-third (30%) of a sample of 10 SHOs were ailed by temporal lobe abnormalities.

In the latter study published in 2003, over one-third of the 33 SHOs studied had received a head injury resulting in unconsciousness prior to offending. Of the nearly 20% of offenders who had experienced a neurological diagnosis, authors stated that epilepsy, brain tumours, and tremors were among those documented. Approximately 64% of SHOs failed neuropsychological tests, which was more than double of the three other comparison groups comprising “sexual aggressives,” “sadists,” and “general sex offenders.”

A seminal compendium of studies authored by Peer Briken, M.D., and associates examining 166 SHOs spanning around one decade has also examined brain abnormalities in this considerably large sample, in addition to investigating the prevalence of paraphilias, sexual sadism, and other features pertaining to the crime of sexual murder. Drawing on findings from neurological imaging, including those from EEG results, has suggested a predictably high degree of anomalous brain physiology and functioning (Briken et al., 2006). Background information suggesting underlying dysfunction revealed the prevalence of head injuries resulting in unconsciousness, epilepsy, meningitis, and hydrocephalus (i.e., inordinate build-up of cerebrospinal fluid within the brain), among others. Of the 60 offenders assessed using brain imaging, 28% revealed frontal lobe irregularities and ventricular dilation, and others. Of the subset (n = 134; 80.7%) of offenders whose brains were examined using the EEG, one in five (21.6%) of the offenders produced anomalous findings. Both epileptiform and paroxysmal abnormalities were noted. The existence of patterns suggesting slowing and nonspecific dysfunctions were also highlighted among the pathological results.