Biosocial Criminology: History, Theory, Research Evidence, and Policy

ABSTRACT

Biological perspectives on criminology were widely accepted in the United States in the late 1800s to early 1900s, but quickly fell out of favor due to eugenicists in the field misusing research and sociocriminologists outside of the field vilifying this avenue of investigation. In recent years, the field has rebounded. This review provides a detailed history of biosocial criminology, exploring its development alongside sociocriminology with a focus on the social and personal histories that contributed to the resurgence of biosocial criminology. A brief and selective literature review follows, providing a general overview of methodologies used in the field, key findings, and policy and practice implications. We conclude by discussing the utility of the biosocial perspective in criminology for studying offending and victimization. We also discuss challenges of applying biosocial research to policy and practice, as well as next steps for the field.

KEYWORDS:

• Biosocial
• biopsychosocial criminology
• history

Biosocial criminology examines interactions between biological and social factors to understand crime (Barnes et al., 2020; Nedelec et al., 2017; Raine, 2013). The application of biology to criminology dates back to the late 1800s with Italian criminologist Cesare Lombroso (Rafter, 1997). Some of Lombroso’s early work described how facial features were associated with criminal behavior. Contemporary biosocial criminology has steered away from such crude explanations of crime (which were often steeped in racist ideas), instead focusing on areas like psychophysiology, neuroimaging, endocrinology, genetics, and nutrition (Portnoy et al., 2018; Raine, 2002a; Raine et al., 2021).

While studying the biological features of criminal behavior is interesting and meaningful work, the policy implications of biosocial criminology are muddied and raise potential moral and ethical concerns. Many fear that eugenics – the process by which unfavorable, heritable traits in the human population are removed by unnatural means (including forced sterilization and sequestering a subset of a given, “unfavorable” population) – is a natural consequence to biosocial research (Hyatt, 1997). After all, the prospect of eliminating crime has been a cornerstone in many ethnic cleansings and widescale sterilizations in human history, including the Holocaust and the eugenics movements in the United States and Sweden (Hyatt, 1997; Rafter, 2004).

Fears of the modern-day application of biopsychosocial criminology, however, must be contextualized with our increased understanding of how heredity, social environment, and neuropsychological functions interact to create human behavior. In order to understand current controversies, findings, and future directions, it is important to understand biosocial criminology’s historical development. The goal of this article is to discuss biosocial criminology’s history as a precursor to present-day research. We first discuss the historical, technological, and sociopolitical contexts surrounding the rise, fall, and resurgence of biosocial criminology, with a focus on the personal and social contexts that drove the development of the field. We then discuss current research that followed early biosocial work within several key domains, including nutrition and hormones, genetics, psychophysiology, brain imaging, and neuroimaging, as well as policy implications within each area. We conclude by identifying broader implications of biosocial research, as well as future directions for the field.

The origin of biosocial theory and its place among American criminology

Biological criminology: 1870s to 1940s

Italian physician Cesare Lombroso is often credited with popularizing the biological theory of crime with his 1876 book Criminal Man (Rafter, 1997; Raine, 2013). Lombroso’s theory was controversial in his native Europe (Wolfgang, 1961) but was popular in the United States. This may be due to concurrent works popular in the United States such as Anatomical Studies upon Brains of Criminals by Moriz Benedickt, published in 1879, and The Jukes: A Study in Crime, Pauperism, Disease and Heredity by Richard Dugdale, published in 1877. These works emboldened champions of the United States’ movement against so-called “feebleminded” individuals who were believed to have a propensity for criminal acts (Rafter, 1997). Lombroso’s theories were in part inspired by Charles Darwin’s On the Origin of Species (published 1859) and The Descent of Man (published 1871), Paul Broca’s work in skull-to-brain ratios, and Franz Gall’s phrenology, arguing that criminals were biological “throwbacks” to earlier versions of man and that this could be observed through what he termed “atavistic” features, such as a pronounced mandible and cheekbones (Rafter, 1997; Wolfgang, 1961). Research failed to support even his more nuanced ideas expressed in his later work, Crime: Its Causes and Remedies (published 1899), which identified social, as well as biological causes of crime (Wolfgang, 1961).

English psychiatrist Charles Goring was an early critic of Lombroso (Driver, 1957; Rafter, 2004). Contrary to Lombroso, Goring found “no such thing as an anthropological criminal type” (Goring, 1913, p. 370) despite his work promoting eugenics, stating that those who were mentally and physically disabled tended to commit more crimes (Beirne, 1988). Goring claimed that Lombroso’s observational methodology was insufficient; rather than describing someone as being above average height or having pronounced cheekbones, Goring felt that actual measurements of these features would be more scientifically rigorous and reproducible (Driver, 1957). In collaboration with statistician Karl Pearson (of the Pearson correlation coefficient), Goring collected anthropometric and conviction data on 3000 incarcerated individuals and non-convicted controls described in The English Convict: A Statistical Study. Goring found that differences in body type were associated with the type of crime the individual committed (Goring, 1913). For example, he argued that convicted individuals measured as much as two inches shorter than controls and weighed up to seven pounds lighter than controls. Goring was one of the first to systematically study and analyze biological traits as they relate to crime, which is unexpected given that he is credited with “closing” the Lombrosian school of thought.

Not to be dissuaded by changing tides, Earnest A. Hooton, a physical anthropologist at Harvard, was largely influenced by Lombroso and Goring and hoped to corroborate differing morphology in criminals (Rafter, 2004). Hooton’s anthropological study of incarcerated people was methodologically flawed, however. The data were inconsistently collected and what was collected was contaminated with opinions and biases of the research staff (Rafter, 2004). Using data collected from over 17,000 participants, Hooton stratified criminals by race, nationality and ethnicity. He expanded upon Lombroso’s idea of a “criminal man” and theorized there must be different types of criminal people, represented by differing morphologies across races. Hooton’s assertion of criminal morphologies among people of all races and his strong condemnation of the Holocaust are cited as reasons why some argue that Hooton was not racist despite being a eugenicist (Rafter, 2004). It was Hooton’s belief that when “low grade” people were negatively impacted by their environment, they committed crime (Hooton, 1939). Thus, the only way to eradicate crime was for these “low grade” individuals to either die (Hooton, 1939) through means of euthanasia or simply not be born through the use of contraceptives and sterilizations (Rafter, 2004). Despite Hooton’s controversial and harmful views, he was, and remains, an influential figure in criminology.

Much of Hooton’s success can be traced to Sheldon Glueck, a former student of the anthropologist. It was Sheldon Glueck who facilitated the professional relationship between Hooton and a Massachusetts State Department of Mental Diseases official, allowing Hooton to gain access to a sample of incarcerated individuals. Hooton too was instrumental in the Gluecks’ relative success,¹ influencing their research of biology and crime (Rafter, 2004). The Gluecks were also influenced by another Hooton mentee: William Sheldon, a psychiatrist and psychologist with an interest in crime (Rafter, 2004). Sheldon popularized somatotyping theory, which argued that human body types caused certain temperaments (Rafter, 2008). The Gluecks corroborated his theory, finding that delinquent children in their Unraveling Juvenile Delinquency study (later expanded on by Robert Sampson and John Laub) tended to be mesomorphic (muscular) rather than ectomorphic (lean; Glueck & Glueck, 1965; Rafter, 2008).

In the 1940s, Hooton, the Gluecks, and Sheldon were subject to intense criticism. Edwin Sutherland, a prominent sociologist, was arguably the loudest and harshest critic (Laub & Sampson, 1991; Rafter, 2004). Sutherland’s analytic induction approach and criminology’s gravitation toward sociology pushed Sutherland to aggressively dismiss any explanation of crime that suggested individual differences (Laub & Sampson, 1991). Sutherland’s denouncement of biological criminology reinforced its waning popularity in the 1930s and 1940s. Concurrently, the eugenics movement in the United States was dying as federal and state eugenics laws were repealed (Hyatt, 1997). These conditions made it possible for sociological theories of crime to dominate criminology while vilifying biological explanations of crime (Lindesmith & Levin, 1937; Raine, 2002b). Though sociological theories still reign in criminology, biological explanations of crime began to gain popularity again in the mid–late 1900s (Rafter, 2004). This resurgence was made possible by a number of scientific advancements and paradigm-shifting works.

Contemporary biosocial criminology: 1950s to present day

While units of heredity were cited or alluded to in early works, how these units – human DNA – looked was a barrier science had yet to overcome. Nearly 100 years after the discovery of deoxyribose nucleic acid, Franklin, Watson, and Crick discovered the structure of the molecule in 1953, opening the door for more advanced genetic studies (NIH, 2019; Pray, 2008). Just 11 years later, Hans Jürgen Eysenck published the first biopsychosocial theory of crime of the 1900s, described in Crime and Personality (Eysenck, 1964) in which he argued that the traits of neuroticism (N) and extraversion (E), and later psychoticism (P) affect social conditioning, in turn affecting impulses that push an individual away from or towards crime (Rafter, 2006). Neuroticism, extraversion and psychoticism were all theorized to be linked to specific brain pathways. Although his theory inspired other biosocial criminologists such as David Farrington and Adrian Raine, Eysenck was the target of criticism from his contemporary sociocriminologists, among them, Edwin Sutherland (Rafter, 2006). It should also be noted that over 50 of Eysneck’s articles have been retracted since 2021 due to concerns over falsified data and lack of transparency in methods according to Retraction Watch. Many of these articles were coauthored by Ronald Grossarth-Maticek and explored themes in health psychology, suggesting that personality traits could influence cancer outcomes (O’Grady, 2020; Pelosi & Appleby, 1992, 1993). Further, Eysneck perpetuated racist beliefs related to race and IQ, rightfully tarnishing his image and influence among modern-day scholars (Colman, 2016). Later in the century, in their influential 1985 book, Crime and Human Nature, James Q. Wilson (a political scientist) and Richard Herrnstein (a psychologist) reinforced psychology and biology’s role in understanding how individual differences lead to crime. This book was highly influential in the resurgence of biosocial criminology.

Around this same time, some of Eysneck’s assertions went on to be partly corroborated by then PhD student, Adrian Raine, and his mentor, Peter Venables. In their 1981 paper, Raine and Venables found that teenage boys from affluent families who were undersocialized (i.e., less prosocial) were poor conditioners to an auditory stimulus as measured by skin conductance response (consistent with Eysneck’s theory), while undersocialized boys from families with lower SES were better conditioned to the auditory stimulus (Raine & Venables, 1981). Raine’s early work with Venables helped set the stage for Raine’s later pioneering work in contemporary biosocial criminology, though his trajectory to becoming a leader in the field was nonlinear (Dooley, 2016). Upon graduating from his PhD program in 1982, Raine worked in prisons as a psychologist for four years, during which he was rejected from 67 academic jobs, which he later attributed to the perceived unpopularity of his research area. In 1986, however, he attended a conference in which the head of the psychology department at the University of Southern California, Robert Hare, urged him to apply for a faculty position in the United States. This chance encounter led Raine to the University of Southern California in 1987. This coincided with the advent of brain imaging, which revolutionized human neuroscience and pushed biosocial criminology to greater heights (Rudo-Hutt et al., 2014). Starting in 1972, computerized tomography (CT scans) allowed physicians to virtually vivisect patients, aiding in diagnosis and treatment (Bhidé et al., 2021a.). Soon, researchers were using the technology along with contrast to image the body. Positron emission tomography (PET) scans are the best example of this technique, using injectable radiotracers to observe anatomical structure and function (Steiner, 2002). Magnetic resonance imaging (MRI) technology quickly followed, but did not gain popularity in U.S. medicine until 1984 (Bhidé et al., 2021b). Researchers in human neuroscience and psychology soon employed these techniques in their own labs. Raine won a small grant at USC to fund brain imaging research and became the first researcher to use neuroimaging in the form of PET scans to study the brains of murderers (Raine et al., 1997). He found that murderers had decreased brain activity (as suggested by decreased glucose metabolism) in several brain regions, including the prefrontal cortex which is responsible for inhibitory control and decision making. This highly influential early work inspired decades of research into the relationship between criminal behavior and brain structure and function.

Concurrently, genetic research in criminology also made strides. For instance, in 1984, Mednick et al. (1984) found that adopted children’s propensity for violent crime was associated with their biological parents’ behavior. In 2002, Caspi et al. published their seminal article in which they found that the gene encoding for monoamine oxidase A (MAOA) interacted with maltreatment to predict antisocial behavior. This article, which has been cited over 6000 times, led to a new wave of research which both attempted to replicate their original gene-environment (GxE) interaction and sought to identify new candidate genes.

Later, in April 2013, United States President Barack Obama announced the BRAIN (Brain Research Through Advancing Innovative Neurotechnologies) Initiative to support exploratory neuroscientific endeavors. In collaboration with the National Institutes of Health (NIH) and the National Science Foundation, among others, the BRAIN Initiative has funded many projects in neuroscience from the molecular level to the behavioral (NIH, n.d.). Later that month, Raine’s book on biological correlations of antisocial behavior, The Anatomy of Violence, was released. The book was geared toward a non-academic audience, communicating science to the general public. Both the BRAIN Initiative and Raine’s book helped elevate biosocial criminology, especially neurocriminological research, among the masses and in the fields of criminology and criminal justice.

As biosocial research in criminology becomes more widespread, more traditional scholars are seeing its utility. First, biosocial criminology can be applied to a wide range of crimes (Raine, 2002b). With all social factors held constant, some individuals from disadvantaged backgrounds will go on to commit crimes, while others will not, suggesting that individual differences contribute to crime causation. Biosocial criminology also acts as a general theory of crime as individual differences can, in theory, contribute to all crime. In his 2010 American Society of Criminology presidential address, Francis Cullen asserted that criminologists “can no longer pretend that biology is not intimately implicated in human behavior and thus criminal behavior” (Cullen, p. 311, Cullen, 2011). While the controversy surrounding biosocial criminology has not disappeared, the influence of biosocial criminology continues to steadily grow (Rudo-Hutt et al., 2014).

Biosocial criminology: A review of research and policy implications

Biosocial criminology makes use of research techniques across several disciplines (Barnes et al., 2015). The following brief research review will highlight findings in five areas: (1) nutrition and hormones, (2) genetics, (3) psychophysiology, (4) brain injury, and (5) neuroimaging (summarized in table 1). The goal of this selective narrative review is to provide a broad overview of contemporary biosocial research. We selected studies published in the past 15 years that are representative of the contemporary trends in biosocial literature and provide a basis for policy implications, discussed at the end of each research area and more broadly in the next section of this paper. Where necessary to contextualize contemporary findings, we also include earlier work that had a strong historical influence on the field. This is not intended to be a comprehensive or systematic review of the whole field, but rather a sampling of representative studies, providing an introduction for those who are new to biosocial research and a broad overview for those that are familiar with this work.

Table 1. Summary of original research reviewed in order of appearance.

Author(s), Year	Biomarker	Key Findings
Nutrition and Hormones
Raine et al., 2015	Omega-3	Children aged 8–16 years had lower externalizing and internalizing behavior as reported by parents after 6 months of omega-3 supplementation.
Jackson, 2016	Nutritional quality	After controlling for genetic and environmental influences, poor nutritional quality during preschool was associated with antisocial behavior in elementary school.
Galler et al., 2012	Nutritional quality	Children’s IQ and home environment partially mediated the association between malnourishment in infancy and conduct problems at ages 11–17 years.
Miyake et al., 2018	Vitamins B9 and B6	Vitamins B9 and B6 intake during pregnancy increased the likelihood of children’s prosocial behavior. B6 was also associated with lower hyperactivity in children. B2 was associated with fewer emotional problems.
Jackson et al., 2018	Food insecurity	Children from food insecure homes had less self-control during early childhood and were more delinquent in late childhood compared with children from food secure homes.
Jackson & Vaughn, 2016	Food insecurity	Food insecurity predicted misconduct in males, but not females.
J. Liu et al., 2012	2D:4D (high prenatal testosterone)	Lower 2D:4D was associated with increased aggression and attention problems in boys, but not girls aged 7–20 years.
Portnoy & Farrington, 2015	2D:4D (high prenatal testosterone) and salivary cortisol	Cortisol reactivity and 2D:4D interacted to predict externalizing behavior in males. Low cortisol reactivity was directly associated with aggression and rule breaking in subjects with low 2D:4D.
Woeckener et al., 2018	Salivary testosterone	Parental rejection and testosterone were associated with antisocial behavior. The association between parental rejection and antisocial behavior was stronger when combined with higher testosterone.
Genetics
Schwartz et al., 2017	Heritability	Subjects with an average amount of self-control had heritability estimates from 43–54%. Subjects with very high or very low self-control had heritability estimates from 6–37%.
Caspi et al., 2002	MAOA gene	Childhood maltreatment x low MAOA allele resulted in higher antisocial behavior in adult males.
Fergusson et al., 2011	MAOA gene	Male subjects who reported childhood abuse and had low MAOA allele were more likely to report offending, conduct problems, and hostility as adults.
Salvatore et al., 2015	GWAS, polygenic risk score (PRS)	PRS for externalizing behavior initially found in adults also predicted externalizing behavior, externalizing disorders, and impulsivity in adolescence and young adulthood after controlling for parents’ externalizing behavior. Adolescent parental monitoring x PRS and peer substance use x PRS predicted externalizing disorders. Single nucleotide polymorphism (SNPs) accounted for 6% of variance in externalizing behavior.
Tielbeek et al., 2017	GWAS, PRS	SNPs accounted for 5% of the variance in antisocial behavior.
Wertz et al., 2018	GWAS, PRS	P for low educational attainment predicted low cognitive ability and low self-control which predicted antisocial behavior.
H. Liu et al., 2021	GWAS, PRS	Participants with low polygenic scores (PS) for educational attainment were more likely to report being involved with the legal system. Further, adolescent legal system involvement x PS for educational attainment predicted actual educational attainment in males.
Ruisch et al., 2020	GWAS, PRS	Dopaminergic, glutamatergic, and neuroendocrine PRS were associated with unemotional scores, explaining 1.33, 2.00, and 1.20% of variance respectively. Dopaminergic PRS x Childhood life events predicted unemotional scores.
Psychophysiology
Zhang & Gao, 2015	Respiratory sinus arrhythmia (RSA)	In a sample of adults, RSA x High social adversity predicted reactive aggression. RSA x Low social adversity was associated with reactive aggression, but negatively associated with proactive aggression.
Fagan et al., 2017	Heart rate (HR)	Low resting HR x Social adversity predicted antisocial behavior in 7–10 year-old boys.
Kochanska et al., 2015	Electrodermal activity/skin conductance	High levels of maternal controlling behavior and low skin conductance predicted higher levels of externalizing behavior in 8–10 year-olds.
Buodo et al., 2013	Electrodermal activity/skin conductance	Children 9–12 years with lower ED reactivity who were also exposed to parenting stress had more externalizing symptoms.
Brain injury
Schofield et al., 2015	Traumatic brain injury (TBI)	TBI was associated with convictions of any kind in males and females. TBI was also associated with violent convictions in males when controlling for genetics (sibling controls).
Ryan et al., 2015	TBI	Pediatric TBI (aged 1–12 years at injury) was associated with externalizing behavior 10 and 16 years post-injury. Externalizing behavior was more frequent in children who had poor adaptive functioning and lower IQ pre-injury.
Silver et al., 2020	TBI	TBIs in adolescence, but not adulthood were associated with more adverse psychological events (e.g., delinquency, bullying, psychopathy, moral disengagement, impulsivity).
Connolly & McCormick, 2019	TBI	TBI was associated with anxiety, depression, aggression, and delinquency 2–2.5 years later.
Vaughn et al., 2014	TBI	TBI was associated with higher impulsivity and negative emotion ratings.
Neuroimaging
Ling et al., 2020	Structural MRI	Girls high in CU traits and boys low in CU had larger right amygdalae.
Kaya et al., 2020	Structural MRI	Participants with antisocial personality disorder had smaller amygdalae and hippocampi than healthy controls.
Kleine Deters et al., 2022	PRS and structural MRI	PRS for antisocial behavior were associated with disruptive behavior disorders, self-reported antisocial behavior and left basolateral amygdala shape.
Glenn et al., 2009	Functional MRI (fMRI)	Participants higher in psychopathy scores has less amygdalae activity during emotional moral decision-making. Individuals high in manipulation, conning, superficiality, and deceitfulness had less activity in the medial prefrontal cortex, posterior cingulate and angular gyrus.
Shenhav & Greene, 2014	fMRI	Amygdala-ventromedial prefrontal cortex connectivity was lowest for pure utilitarian assessments and highest for pure emotional assessments.
Marsh et al., 2013	fMRI	Youths with psychopathic traits had reduced activity in the rostral anterior cingulate cortex, putamen, and amygdala, all of which are brain regions associated with pain empathy.

Nutrition and hormones

Nutrition

The chemical agents that humans consume and endogenously produce have an impact on behavior. Inadequate ingestion of certain micronutrients, trace elements, and highly unsaturated fatty acids (HUFAs) has been linked to sub-optimal brain development and cognitive deficits (Gómez-Pinilla, 2008; Gow & Hibbeln, 2014). Most research to date in the area of nutrition and antisocial behavior has focused on omega-3 high unsaturated fatty acids. For instance, the longitudinal Mauritius Child Health Study found that poor nutrition at age three years predicted antisocial behavior at age 17 years (Raine et al., 2003). This Mauritius study also involved a randomized controlled trial of omega-3 supplementation in a community-based sample of 200 children ages 8–16 years. Children who were randomly assigned to receive omega-3 supplementation showed reductions in caregiver-reported externalizing and internalizing behavior six months post-treatment (Raine et al., 2015). Recent research has built upon this work. A meta-analysis found that omega-3 fatty acid consumption was associated with reduced aggression (Gajos & Beaver, 2016). Conversely, malnutrition in preschoolers was found to be associated with higher levels of antisocial behavior even when controlling for heredity (Jackson, 2016). Research indicates that this relationship between malnutrition and externalizing behavior can start at infancy and continue into adolescence (Galler et al., 2012). These results suggest that poor nutrition may contribute to negative emotionality. Further, it is possible that environmental factors, like food insecurity, may contribute to biological issues resulting from poor nutrition that promote antisocial behavior. Indeed, food insecurity has been linked to concurrent childhood and adolescent misconduct, especially in boys (Jackson & Vaughn, 2017) and low self-control and early delinquency (Jackson et al., 2018).

Implications for policy and practice

Policy interventions that focus on providing children with nutritious meals may help decrease antisocial behaviors in adolescence and adulthood as proper nutrition has been shown to improve brain development and behavior (Tanner & Finn-Stevenson, 2002). The United States federal government currently has several programs (Supplemental Nutrition Assistance Program [SNAP], Women, Infants and Children [WIC], School Breakfast and National School Lunch Program; USDA Nutrition) aimed at increasing food security for children. Some school districts in the US provide children with meals when school is not in session. While a harm reduction strategy is helpful in making sure children are fed regardless of the nutritional value of the food, investing more money and resources into providing children with enriched foods or meal supplements through their schools could increase food equity. In addition, it is possible that improved prenatal maternal nutrition could curb antisocial behavior in childhood with research showing that higher folate, vitamin B₆, and vitamin B₂ consumption in pregnancy were associated with an increased likelihood of offspring prosocial behavior (Miyake et al., 2018). Though more research is needed on the effects of maternal prenatal nutrition on child behavioral outcomes, better prenatal nutrition is likely to have wide-ranging beneficial health effects.

Hormones

Hormones are other chemical agents that can impact behavior. Among the many hormones that have been examined in relation to antisocial behavior, testosterone is likely the most widely studied. Testosterone is the end product of the hypothalamic-pituitary-gonadal (HPG) axis and is the primary androgen, the group of steroid hormones responsible for the development and maintenance of masculine traits (Mazur & Booth, 1998). Testosterone is thought to have both organizational effects on behavior through its effects on neurodevelopment during gestation and activational effects that occur through the influence of postnatal circulating testosterone (Breedlove, 2010; Mazur & Booth, 1998). Directly studying the organizational effects of testosterone is difficult as measuring testosterone in-utero requires amniocentesis, which is invasive and potentially risky. Instead, researchers have found that the second-to-fourth digit ratio of the hand (2D:4D) may be a marker of prenatal testosterone levels, with a lower 2D:4D indicating higher exposure to prenatal testosterone relative to estrogen (J. Manning et al., 2014; J. T. Manning et al., 1998). Low 2D:4D has been linked to higher levels of externalizing behavior (J. Liu et al., 2012). However, a meta-analysis of 2D:4D and aggression and violent behavior found that this relationship was significant, but small, raising questions about the usefulness of 2D:4D as a risk factor for aggression (Turanovic et al., 2017). It is possible that 2D:4D interacts with other hormones to predict behavior, with one study finding that testosterone and cortisol interacted to predict aggressive behavior in adolescence (Portnoy & Farrington, 2015). This is consistent with past research, which suggested that while testosterone was associated with dominance, it was more predictive of aggression when considered alongside low serotonin or cortisol (Glenn & Raine, 2008).

In addition to studying 2D:4D, researchers have also examined the relationship between antisocial behavior and circulating levels of testosterone. As with 2D:4D, a meta-analysis found that baseline testosterone was significantly associated with aggression, though this relationship was weak and only significant for males (Geniole et al., 2020). It is possible that social contexts may help to explain heterogeneity in results of studies on testosterone and aggression. One study found that testosterone levels in young adults moderated the relationship between parental rejection and antisocial behavior (Woeckener et al., 2018). Individuals who had low levels of testosterone reported low levels of antisocial behavior regardless of parental rejection, suggesting that low testosterone could be a protective factor against antisocial behavior. Conversely, individuals with high levels of testosterone and high parental rejection reported antisocial behavior at higher levels than those with high testosterone and low parental rejection. The results illustrate how biological factors can set the stage for how social conditions influence behavior.

Implications for policy and practice

While hormones may have large effects on behavior, such as the “roid rage” that results from abusing synthetic testosterone in the form of anabolic steroids (Corrigan, 1996), therapies targeting testosterone have not always been successful or ethical, which may be in part due to the inconsistent relationships between testosterone, offending, and externalizing behavior. Furthermore, treatments that lower testosterone can have serious side effects, including loss of bone mass, diabetes, pulmonary embolism, and depression, all of which could be life threatening and/or debilitating (Stinneford, 2006). An alternative course of treatment could be to target other hormones or neurotransmitters such as serotonin, which has been found to interact with testosterone (Trifu et al., 2020). However, serotonin-focused pharmacological interventions for antisocial behavior have mixed results with some finding serotonin increases aggression and others finding it is protective against aggression and antisocial behavior (Coccaro et al., 2015; Duke et al., 2013; Khalifa et al., 2010). Rather than focusing on pharmacologic interventions, it may be more useful to utilize behavioral or psychosocial interventions that may affect hormone levels, such as mindfulness meditation or cognitive behavioral therapy, though their effects on hormones require additional research (Duke et al., 2013; Manigault et al., 2019).

Genetics

Behavioral genetics – which is a somewhat controversial field due to its historical connection to eugenics – attempts to estimate the degree of heritability of behavior (Berryessa & Cho, 2013). Scientists believe that this jump from genetics to eugenics stems from the general public’s misunderstanding of genes and behavior (Berryessa & Cho, 2013). Many equate genetics with biological determinism, unaware of epigenetic changes to gene expression; others may wrongly assume that all genetic researchers ignore the importance of environmental influences. Research linking behavior to genes has shown that gene-environment interactions are important to understanding behavior (Moffitt, 2005) – nature and nurture are instrumental in development.

Family studies are often used in behavioral genetics research (Berryessa & Cho, 2013). Twin studies are powerful at estimating the extent of environmental versus genetic influences, because monozygotic (identical) twins are genetically identical, while dizygotic (fraternal) twins only share about 50% of their genes. Studies with siblings can also be useful since siblings can be expected to share about half of their genes.² Finally, there are adoption studies in which twins or siblings are adopted into different homes, allowing the effects of nature versus nurture to be determined. Thankfully, these studies are rarely orchestrated the way they were decades ago due to ethical concerns with purposefully splitting up families that could overwise remain united (see, Hoffman & Oppenheim, 2019), though they are still illuminating from a scientific standpoint.

Twin and adoption studies have shown that there is substantial genetic influence on antisocial behavior. In an influential meta-analysis, Rhee and Waldman (2002) found that approximately 41% of the variation in antisocial behavior was attributable to additive and nonadditive genetic influences. A more recent meta-analysis found that 56% of the variance in antisocial personality and behavior could be attributed to genetic influences (Ferguson, 2010). Behavioral genetics studies have also examined constructs thought to be involved in the etiology of criminal behavior. Self-control, which is often negatively associated with delinquency and crime, has been found to have a heritable component. Schwartz et al. (2017) studied monozygotic and dizygotic twins to derive hereditability estimates for self-control. Those who had an average amount of self-control were found to have hereditability estimates between 43% and 54%, meaning genetic influences explained about half of the variation in self-control between individuals in the sample. Those with very high or very low self-control had smaller heritability estimates, ranging from 6% to 37%. These results suggest that low and high self-control may be differentially affected by socialization when compared to average levels of self-control.

Possibly the most reproduced finding in the realm of molecular genetics and criminology is the link between candidate gene monoamine oxidase (MAOA), child adversity, and antisocial behavior (especially in boys and men), initially proposed by Caspi et al. (2002). MAOA has been nicknamed the “warrior gene” as individuals with low variants of this X-chromosome linked gene have been reported to have higher levels of aggression, especially when exposed to childhood adversity (Fergusson et al., 2011). For example, Fergusson et al. (2011) found that men who experienced child abuse and had the low variant of the MAOA gene developed antisocial behaviors that were observable in their 30s. A meta-analysis found that the original GxE interaction reported by Caspi et al. (2002) was replicated in studies of males (Byrd & Manuck, 2014). These behavioral issues may be caused by the lack of neurotransmitter degradation made possible by the MAOA protein, which may be exacerbated in the presence of an adverse social environment.

Whole-genome studies quantifying individuals’ propensity to exhibit a behavior (e.g., aggression) or behavioral profile (e.g., antisocial behavior, psychopathy) through polygenic risk scores have become more popular in recent years (Beaver et al., 2018). Unlike candidate gene studies, polygenic risk scores describe genetic variants across the genome that have been identified through genome-wide association studies (GWAS) to push someone toward or away from a medical or behavioral outcome. In candidate gene studies, prior knowledge of the gene of interest is needed. Many behaviors, however, are not linked to just one gene. In this way, GWAS can reveal more information about the association between genes and behavior. By summing risk alleles (which have relatively low effect sizes on their own) that are associated with a given behavior, a polygenic risk score can be calculated (Choi et al., 2020). Heritability estimates of antisocial behavior based on polygenic risk score analysis have been reported to be low, but with more research this estimate is expected to rise to 50% (from 5–6%; Salvatore et al., 2015; Tielbeek et al., 2017). Regarding aggression, heritability estimates based on polygenic risk scores have been reported to be up to 50% (Odintsova et al., 2019), reinforcing that estimates of antisocial behavior may grow as researchers conduct more GWAS with larger, more diverse samples.

Some researchers have explored how polygenic risk scores for other social behaviors, namely educational attainment, could predict antisocial behavior or involvement with the criminal legal system. Wertz et al. (2018) found that polygenic risk scores for low educational attainment were associated with low cognitive ability, low self-control, and academic difficulties in two samples in New Zealand. In turn, low cognitive ability and self-control, as well as academic difficulty predicted life course persistent antisocial behavior. Similarly, H. Liu et al. (2021) found that low polygenic risk scores for education attainment predicted adolescent criminal legal system involvement in an American sample. Aside from educational attainment, polygenic risk scores for the glutamatergic, dopaminergic and neuroendocrine systems have also been found to predict antisocial behavior in the form of callous-unemotional traits in Dutch children (Ruisch et al., 2020). Taken together, these results suggest that there may be multiple genetic pathways in terms of polygenic risk scores that can explain why antisocial behavior develops and persists.

Implications for policy and practice

Polygenic risk scores may aid public policy by fostering understanding in the general public (Graham et al., 2021). As Graham et al. (2021) point out, public opinion is the backbone of public policy and the criminal legal system. For instance, in criminal proceedings defendants are judged by a jury of peers, and the prior knowledge of jurors affects their judgments even after expert testimony is heard. In their study, Graham et al. (2021) found that individuals who believed in the mythical “crime gene” also believed that offenders are less capable of change. They also found that those who believed in multiple genes causing crime were more likely to support harsh punishments for offenders in the form of social exclusion post-incarceration, though other studies have indicated that knowing the genetic basis of crime resulted in support for lesser punishment of psychopaths (Aspinwall et al., 2012) and others who have committed crimes (Cheung & Heine, 2015) because genetic factors were seen as mitigating circumstances. More research should be conducted to better understand how other factors (e.g., educational attainment, race, experience with incarceration) interact with the knowledge of the genetic basis of crime to affect opinions regarding genes and behavioral culpability.

While GWAS have the potential to contribute to the equitable treatment of justice-involved individuals, there are also potential negative consequences to such information being widely available, especially to individuals who do not view polygenic risk scores with the nuance they require. For instance, Berryessa and Cho (2013) mention that whole genome sequencing is becoming more available to the public which may affect parents’ decisions about their children with “high” polygenic risk scores for antisocial behavior. Parents may seek unnecessary psychiatric treatment for their children in an effort to prevent antisocial behavior, or they may parent one child differently compared with another child who does not have the same risk scores. Another cause for concern is the military’s potential use of genome wide sequencing in the hopes of creating the best soldier – smart, strong, obedient (Berryessa & Cho, 2013). Conversely, there are applications of genetics that can enhance treatment options. Understanding an individual’s genetic make-up, including family history and genome sequencing, could aid in determining which medications are more likely to resolve psychiatric issues (including but not limited to antisocial tendencies), reducing the trial-and-error that typically occurs when starting a new medication (Kendler, 2006). Genetic testing could also help physicians make diagnoses for psychiatric disorders (Demkow & Wolańczyk, 2017) like oppositional defiant disorder, antisocial personality disorder, and conduct disorder. The extent to which genetic testing will be used to make decisions surrounding antisociality, justice, and crime is unknown, thus individuals in the field are advised to consult bioethicists in their writings and practice.

Psychophysiology

Psychophysiology involves the use of noninvasive measures to assess baseline physiological states and nearly immediate physiological responses to environmental stimuli. Many psychophysiological studies have examined biosocial interactions. Psychophysiological studies have given insight into how environmental conditions can affect a child’s nervous system which can in turn impact behavior. Among the psychophysiological risk factors for antisocial behavior, low resting heart rate is considered the best-replicated (De Looff et al., 2022; Ortiz & Raine, 2004; Portnoy & Farrington, 2015). Cardiac measures have also been widely examined in interaction with social risk factors (Barnes et al., 2020; Van Hazebroek et al., 2019). For example, Zhang and Gao (2015) found that resting respiratory sinus arrhythmia (RSA) and social adversity interacted to predict reactive aggression. Similarly, the interaction of low resting heart rate and social adversity has predicted antisocial behavior in young boys (Fagan et al., 2017). Studying such interactions is important as they more closely represent the social and biological inputs that influence behavior (Barnes et al., 2020).

Low skin conductance reactivity is also associated with a higher risk for antisocial behavior (Ling et al., 2019). In a relatively recent study, Kochanska et al. (2015) found that high levels of maternal controlling behavior over children when coupled with low skin conductance predicted higher levels of externalizing behavior among children aged 8–10 years. Buodo et al. (2013) found further evidence that suggests a relationship between parental stress, skin conductance responses and externalizing behavior in children ages 9–12 years. They found that sympathetic reactivity as measured by skin conductance responses moderated the relationship between externalizing behavior and parental stress; externalizing behavior and parental stress had a positive relationship that was strengthened by lower skin conductance responses. These findings align with the theory that low sympathetic nervous system reactivity is associated with high levels of externalizing problems. The results also reinforce biology-environment interactions as a trigger for criminal risk.

Implications for policy and practice

Policy implications should take into consideration the interactions between psychophysiological risk factors and the environment, as evidence suggests that resting psychophysiological states can be influenced by the social environment, especially in youth (Barnes et al., 2020; Portnoy, Cui et al., 2020; Scarpa, 2003; Van Hazebroek et al., 2019). For example, exposure to violence is theorized to cause physiological desensitization in children, which may facilitate their antisocial behavior in the future by way of sensation seeking behaviors (Scarpa, 2003). Based on this, Scarpa (2003) has suggested the use of parenting programs and home-based nursing programs to support and enrich the family environment, as well as policies that target bullying and firearm safety. Biofeedback programs that teach individuals to identify physiological states associated with externalizing behavior may be an additional policy implication. In their preliminary research, Blankendaal and Bosse (2018) found that a virtual reality aggression de-escalation paradigm helped increase users’ awareness of their emotional states through reporting electrodermal activity in real time. Additionally, programs that encourage physical exercise or activity that temporarily raise heart rate through prosocial means may help to reduce antisocial behavior in children with low resting heart rate.

Brain injury

Traumatic brain injury (TBI) is a medical diagnosis that is over represented among the justice-involved population (Williams et al., 2010). Research indicates that after a TBI, individuals are more likely to engage in antisocial behavior and become involved with the law. A study found that men with TBI were at a higher risk for being convicted of violent offenses while women were not after controlling for genetic influences (Schofield et al., 2015). Another study conducted with juveniles showed that sufferers of pediatric head injuries were at an elevated risk for displaying externalizing behaviors, and this risk was compounded by poor adaptive functioning and lower IQ present before injury (Ryan et al., 2015).

Research using data from the Pathways to Desistance Study which followed justice-involved adolescents in Philadelphia and Phoenix, found that youth who experienced TBIs had higher levels of delinquency, bullying, psychopathy, moral disengagement, and impulsivity than participants without TBIs (Silver et al., 2020). TBI has also been linked to poor mental health outcomes like anxiety and depression which may lead to externalizing behaviors like delinquency, bullying and crime (Connolly & McCormick, 2019; Silver et al., 2020). People who experience a TBI in childhood have also been found to have poorer long-term psychological outcomes than those who experience TBIs later in life (Silver et al., 2020). Research from the Pathways to Desistance Study found that TBI was more common among adolescent boys than girls. Further, boys who identified as Black and Hispanic reported TBIs at rates higher than their White counterparts (Vaughn et al., 2014). Given the links between TBI and antisocial outcomes, it could be the case that elevated rates of TBI in part account for higher rates of incarceration among Black and Hispanic males, though this remains speculative.

Implications for policy and practice

While TBI cannot and does not account for all crimes that are perpetrated, the link between TBI and crime is interesting and has implications in better neurorehabilitation after brain injury. For example, otherwise idiopathic aggression, disinhibition and emotional issues, diagnosed as posttraumatic agitation, is a concerning outcome of TBI with few current pharmacological remedies (Oberholzer & Müri, 2019). Research into behavioral and familial interventions that could possibly reduce posttraumatic agitation may help to prevent persistent antisocial behavior. Also implicated in this research is the need to educate parents and children on the behavioral risks, in addition to medical risks, of sustaining a head injury. All 50 states in the US and Washington D.C. currently have laws regarding TBI awareness in school and/or best practices for student athletes post-concussion (NCSL, 2018), but physicians and school officials should also encourage parents and caretakers to monitor children’s personality and behavior after a head injury. Indeed, frequent behavioral evaluations after a TBI are recommended for physician practice, though allied healthcare professionals and social support staff could also administer scales, such as the Richmond Agitation Sedation Scale, to create a multi-prong approach to monitoring and treating TBI-related aggression (Oberholzer & Müri, 2019). With this knowledge, individuals who are exhibiting externalizing behavior as a result of a head injury may be able to receive psychological and/or psychiatric help early on, reducing the severity of antisocial behavior later in life.

Neuroimaging

Structural brain imaging is a commonly used technique to explore neural correlates of antisocial behavior. One brain region that has been examined in relation to antisocial behavior is the amygdala. The amygdalae are almond-shaped brain structures on either brain hemisphere that contribute to emotion, including fear. Kaya et al. (2020) found that individuals with antisocial personality disorder not only had smaller amygdalae, but also smaller hippocampi volumes. More recent research has supported that genetic risk for antisocial behavior is related to amygdalae morphology (Kleine Deters et al., 2022), reinforcing the link between antisociality and the amygdala.

Functional brain imaging, particularly fMRIs, has been used to examine cognition associated with crime (Greely & Farahany, 2018) such as moral attribution. In a 2019 article, Raine outlined his neuromoral theory of antisocial, violent, and psychopathic behavior, identifying the prefrontal cortex, amygdala and the superior and temporal gyri as areas of interest regarding hypoactivation of the brain. Glenn et al. (2009) have found support for this theory, finding that participants with high levels of psychopathy had lower activity in the amygdalae during moral decision making. Shenhav and Greene (2014) also found that amygdala-ventromedial prefrontal cortex connectivity was implicated in moral decision making, though their study revealed that this pathway was more involved in non-utilitarian, emotional moral appraisals. Regarding antisocial populations, perhaps the lack of amygdala activation indicates a lack of empathy. Indeed, in a study with 14-year-old youth, Marsh et al. (2013) found that participants with more psychopathic traits showed reduced activity in the amygdala and other brain regions associated with empathetic pain responses when viewing photos of bodily injuries.

Implications for policy and practice

Brain imaging studies often suffer from small sample sizes due to cost, time to retrieve sample, and/or extensive screening (participants are limited based on past medical procedures, neurotypicality, handedness, etc.; Hanspach et al., 2021). This may limit the generalizability of findings from these studies. Despite these limitations, neuroimaging has implications for policy and practice reducing antisocial behavior. For example, Bufkin and Luttrell (2005) suggested that imaging can be used to inform risk assessment tools. Today, biosocial factors are still not incorporated in risk assessments (Boisvert, 2021) and large neuroimaging studies may be better used as a predictors of crime trends rather than individual risk (Greely & Farahany, 2018) in turn helping medical, psychological, and social services anticipate resource and workforce needs.

Regarding individuals in the legal system, neuroimaging can serve as evidence for mitigating circumstances, insanity, and mental disability (Greely & Farahany, 2018). Using neuroimaging in this way could contribute to equitable sentencing and more appropriate treatment for justice involved individuals. Neuroimaging can also inform treatments to prevent the escalation of antisocial behavior. For example, neuroimaging has been used to examine how pharmacological interventions affect individuals with borderline personality disorder (Cattarinussi et al., 2022). Similarly, research exploring neurochemical pathways in individuals with antisocial behavior could lead to pharmacological interventions that allow individuals to interact with society in a healthy manner that does not put them at risk for incarceration. Neuroimaging also allows for the identification of abnormalities in the brain that are related to maladaptive behavior which can then be targeted for treatment. The prefrontal cortex has consistently been found to be an area of reduced gray matter in those with antisocial behavior (Raine et al., 2000; Yang & Raine, 2009; Yang et al., 2009, 2010). Research has found that stimulation of this area via transcranial direct current stimulation (tDCS) reduces aggressive intentions (Choy et al., 2018; Gilam et al., 2018; Sergiou et al., 2022). While more research should be done on the clinical implications and long-term outcomes of tDCS therapy on antisocial behavior, this treatment could possibly be as successful in reducing antisocial behavior as it has been in treating depression (Palm et al., 2016).

Strengths, limitations, and future biosocial research

While biosocial research has illuminated many mysteries of behavior, it has also sparked more questions about the link between biology, social environment, and resulting behaviors. The extent to which certain biological processes contribute to behavior is unknown, and researchers often disagree. For example, there have been criticisms against functional brain imaging citing shoddy statistics and arbitrary identification of neural networks as reasons to doubt findings published by so-called “blob-ologists” (Hanson, 2022). Critics question whether small differences in activation give much insight into human behavior and cognition. Imaging studies typically cannot determine the effects of other factors that may affect the neural structures of interest, such as the social environment or in-utero environment. Another issue is differences in methodology. For instance, two scales may yield differing outcomes even if the construct they are meant to measure is the same (Barnes et al., 2020). Another methodological issue is that many genetic studies have established zygosity based on questionnaires or appearances even though these techniques are not as reliable as genetic testing (Cutler et al., 2015; Little et al., 2016; Walters & White, 1989). This calls into question how robust twin studies are and how they inform current studies. In addition, biosocial models are vulnerable to misuse in ways other criminological theories and schools of thought are not. Critics are often afraid that biosocial research is one step away from creating more justifications for discrimination under the guise of biology (Miley & Shreve, 2020). After all, European colonization of the Americas was predicated on genocide (by way of the mestizaje, slaughter, displacement and/or biological warfare) and justified by dehumanization on the basis of race.

While biosocial theory is subject to more scrutiny than societal theories of crime, biomarkers are not necessarily more determinant of crime than are social risk factors (Barnes et al., 2020). Social adversity, such as poverty and parental incarceration, is perceived to be something that people can overcome if they are gritty and resilient enough. This, despite that up to 46% of children who experience moderate–to–high levels of poverty grow to be impoverished adults (Wagmiller & Adelman, 2009). Intergenerational incarceration is also common, with children of incarcerated adults being six times more likely to become incarcerated themselves. Despite this, the public tends to see these risk factors as more surmountable than biological risk factors or biomarkers (this is not to say that social risk factors of crime do not carry stigma or cannot be surmounted of course). This misconception is perhaps the largest hurdle biosocial criminologists face. For this reason, biopsychosocial criminological theories may not need to be revised as much as they need to be rebranded to better represent the intentions of researchers in the field and our modern understanding of how nature and nurture interact within individuals. With more research and science outreach, it will be possible to uncover and clarify patterns in human behavior and work toward creating effective responses to crime.

Applications, concerns, and future steps of biosocial research

After examining the past and current state of the field, we now turn our attention to the implications of biosocial criminological research and future steps for researchers. In this section, we discuss broad applications of biosocial criminology to crime prevention (i.e., offending) and victimization. We also focus on two especially concerning unintended consequences of doing work in this field: eugenics and miscarriages of justice. We conclude with recommendations for researchers in the field in the hopes that history can inform the future.

Implications for crime prevention and mitigation

In the previous sections, we provided specific policy recommendations based on research in each of the domains reviewed. In this section, we discuss broader implications of biosocial criminology as a whole for preventing offending and antisocial behavior. Research has illustrated time and again that biology is changeable. The social environment works in tandem with the body to create individuals that are, in theory, well adapted to their environments. This biological adaptation and plasticity peaks in childhood, making early-life prevention and promoting typical, healthy biological development the most important policy implications to come from biosocial criminology (Rocque et al., 2012; Vaughn, 2016). The nervous system changes in response to the environment. Once certain maladaptive patterns are set, it can be difficult to break out of them in adolescence and adulthood (Moffitt, 1993). Adverse childhood experiences can mold a child to be adaptive in an abusive environment, but once that child grows up, their once adaptive callousness and blunted nervous system reactivity can lead to antisocial behaviors, and even crime. Indeed, childhood maltreatment has been associated with an increased risk of juvenile and adult crime (Fitton et al., 2020; Widom, 2017). Possible solutions may include mental health and emotional support services to help parents manage life stressors (O’Reilly et al., 2010) or programs such as the Nurse-Family Partnership, which has resulted in lasting improvements for child emotional development by providing families with prenatal and postnatal support (Olds, 2006). Besides parents, other trusted adults in children’s lives can be educated on the risks of antisocial and criminogenic behaviors in children in order to intervene early. If children are flagged for behaviors that are predictive of antisocial behavior like bed wetting, animal cruelty, fire-starting (Parfitt & Alleyne, 2018) and/or lack of empathy (Frick & Kemp, 2021), they can be assessed and treated for antisocial behavior. Research suggests that understanding an individual’s physiology can aid in creating individualized treatment plans (Barnes et al., 2020). Those with low physiological reactivity have been found to be more resistant to interventions against antisociality, suggesting that distinct therapeutic approaches for people with differing baseline levels of activation may be needed (Barnes et al., 2020). Thus, biomarkers can help create targeted treatments and interventions for children and adolescents, and also adults who were not able to get treatment at a younger age. Other possible treatments include teaching self-regulation techniques and effortful control, decreasing negative emotionality, and increasing empathy through cognitive behavioral therapy (Vaughn, 2016). Another treatment that could be explored is omega-3 supplementation to reduce antisocial behavior in children and adults (Portnoy et al., 2018; Raine et al., 2021). These treatments exemplify that biosocial work not only supports early life interventions, but can also inform treatment throughout the life course.

Implications for victimization

Often, victims and offenders are not distinct classes (Berg & Mulford, 2020; Hosser et al., 2007; Jennings et al., 2012). This overlap may occur when individuals who engage in crime associate themselves with individuals who in turn could victimize them. Though the victim-offender overlap varies based on offense (for example, about half of homicide victims have a prior arrest history), most research on the victim-offender overlap finds at least some support for the phenomenon (Jennings et al., 2012). Victimization (Baldwin et al., 2018; Trotta et al., 2021) and exposure to violence at a young age (Rasmussen et al., 2020) have been associated with inflammatory biomarkers, as have impulsivity (Gassen et al., 2019) and aggression (Manchia et al., 2019), suggesting that victimization and offending may manifest in similar ways biologically. Psychosocial risk factors for victimization also have a large overlap with risk factors for offending, such as adverse childhood experiences (Beckley et al., 2018), and impulsivity (Connolly et al., 2020). Thus, efforts to decrease biological and social risk factors for offending may not only reduce the incidence of offending, but also victimization.

Biosocial criminological research goes beyond explaining the victim-offender overlap, having implications for the identification and treatment of victims. For example, victims of intimate partner violence strangulation have been found to be at a higher risk of experiencing subsequent stroke and cognitive delays (Patch et al., 2018). Despite this, very few victims of intimate partner violence seek medical help after being victimized, in part because victims may not know the risks. Fewer even are asked about strangulation injuries, with the most popular abuse screening tool, the Abuse Assessment Screen, still not including choking despite calls for its revision (Laughon et al., 2008). A better understanding of biological and psychological outcomes of intimate partner violence can help criminologists, social workers, and medical providers communicate with victims about seemingly innocuous injuries, encouraging them to seek medical attention when it is a safe option. Screening tools can also be improved with an increased understanding biological risk factors for abuse perpetration. For instance, victims can be probed on whether their partner has suffered from head injuries, alcoholism, and drug addiction (CDC, 2021). Interdisciplinary research in victimization, neurobiology, and cognition has also yielded treatments for victims who have experienced traumas. In their study, Holmes et al. (2009) found that playing Tetris for 10 minutes after an acute trauma reduced the incidence of flashbacks one week later. This finding has since been replicated with victims in emergency departments seeing reduced flashbacks at one-month post-treatment (Iyadurai et al., 2018). By flooding the brain with images that require visuospatial attention, victims of traumatic events are able to interrupt the encoding of images related to their traumatic experience. This is just one example of the ways that understanding biological processes related to victimization can lead to effective treatments.

Misuse of biosocial criminology and unresolved questions

Currently there are no official programs or policies that use biology as a crime control measure, but there have been reports of forced sterilization among incarcerated people, an example of modern-day eugenics (Johnson, 2013; Medosch, 2021). Women in the United States justice system, as well as ICE internment camps have reported being intimidated, coerced, or deceived into giving consent for hysterectomies and tubal ligations (Johnson, 2013; Medosch, 2021). One physician explained that he wanted to alleviate the burden that these women have on the welfare system by providing these unwanted reproductive services, but his actions appear to be an independent revival of the eugenics movement (Johnson, 2013). This case exemplifies the valid concerns many hold regarding research that examines biological correlates of behavior, especially undesirable behaviors. Eugenics has inspired forced sterilization and sexual selection to breed out unwanted traits, like crime (Hyatt, 1997). A eugenics movement occurred in Sweden starting in the 1930s that specifically targeted those with a “sub-standard” intellect, poor eye sight, and an “unhealthy sexual appetite.” In the early 1900s in the United States, the eugenics movement tried to purge society of disease, crime, and poverty. Both Sweden and the United States used forced sterilization in an attempt to meet this goal until the laws were repealed about 40 years after the start of the movement (1979 in Sweden and around 1940 in the United States; Hyatt, 1997). Eugenics fell out of favor as victims of these forced sterilizations began to speak out about the injustice they faced at the hands of their own government. Today, it is important to educate the public on biological disinformation as one step in preventing a resurgence of eugenics movements. Biosocial researchers should also be aware of the potential for misuse of their research and make active efforts to explain in an easily understood way why their research should not be used toward this end.

Concerns for judicial practice

There continue to be controversial applications of biosocial criminological research, and more broadly, the use of biometrics in the criminal legal system. The recent capture of the Golden State Killer has raised ethical questions regarding mass surveillance and the forensic use of genealogical data (e.g., Ancestry, 23andMe; Guerrini et al., 2018). Though many submit their DNA with the intentions of finding relatives, discovering their ethnic background, or exploring health markers, long user agreements obfuscate the reality that genetic information is purchasable, and family trees on these websites are often public by default. This issue could be remedied by requiring customers to provide consent for their genealogical data to be used forensically, though the lack of governmental oversight of these companies makes this solution difficult to be implemented in the United States.

Another issue overlapping biometrics and the criminal legal system is the use of biomarkers (i.e., heart rate, nervous system reactivity, genetics, neuroimaging) in determining punishment (Boisvert, 2021). While the integration of biomarkers in risk assessments has been promoted by the National Institute of Justice (NIJ; Boisvert, 2021), using biomarkers to determine treatment while individuals are incarcerated could be problematic. Some biomarkers, such as resting heart rate, have been found to vary by race (Portnoy, Jennings et al., 2020) or activity level (Boyett et al., 2013) creating an opportunity for inequitable treatment recommendations. Another concern is that incarcerated individuals may not be able to consent to treatment informed by biomarkers either because it is mandated by a judge or because they feel coerced by virtue of being incarcerated. Instead, we recommend reserving biomarker-informed treatments for individuals who have not been adjudicated, but may be on the trajectory of legal system involvement, such as juveniles with conduct disorders. This approach allows parental consent and child assent to be freely given and withdrawn without the fear of legal repercussions, in turn limiting the opportunity for biological data to be misused in a legal context.

Lastly, there are questions about how biosocial research should be used in the courtroom. For example, the diagnosis of chronic traumatic encephalopathy (CTE) poses interesting legal questions. CTE is an advanced form of TBI that currently can only be diagnosed through post mortem brain autopsies (Lindsley, 2017). The disease is similar to Alzheimer’s dementia: both are characterized by poor memory, aggressive and violent behavior/outbursts, and the accumulation of tau proteins in the brain. Other characteristics of CTE include issues with impulse control and decision making. Given all of the criminally-associated behavioral features of CTE, CTE could likely serve as a mitigating circumstance in a court of law. In the case of Aaron Hernandez, a football player for the New England Patriots who was arrested and charged with the death of Odin Lloyd, his soon to be brother-in-law, his erratic behavior and history of TBI served as evidence in the court of public opinion that he was not completely responsible for his violent behavior (Gregory, 2020). Upon Hernandez’s death by suicide, an autopsy was performed which confirmed the suspicions of many – Hernandez had a very advanced case of CTE (Belson, 2017). As the disease is better understood, it may become a valid legal defense; as of now, however, CTE is arguably an inappropriate piece of evidence to tout in a court of law as the lines between disease and personal responsibility are blurred.

It is also important to consider that while TBI and aggression are associated with one another, it is likely that some aggressive people put themselves in risky situations that result in them having a TBI. In other words, individuals with CTE may have already been at risk for violent behavior, but head injuries exacerbated the aggression, rather than causing it. In that case, the individuals would still be responsible for their actions, head injured or not. As of 2018, 10–12% of murder trials in the United States and 25% of death penalty trials have introduced neurological evidence with the goal of reducing the harshness of the sentence (Greely & Farahany, 2018). Neurological evidence has also been used in assault, drug, robbery, rape, and fraud trials, among others. The ethical ramifications for some of these defenses are gray. Neuroscience cannot help a jury determine what was on the mind of the defendant at the time of the crime, but it can contextualize why a defendant (re)acted in a particular way. In extreme cases like tumors, and degenerative brain diseases that lead to crime, neuroscience could be used to advocate for medical treatment of an individual and a lesser sentence (Greely & Farahany, 2018). However, if a brain bleed is found after a crime is committed, it would be difficult to determine whether the brain bleed was present before the crime and whether the brain bleed influenced the crime. Surely as our knowledge of neurobiological influences on crime increases, our application of neuroscience to the law will improve as well.

There are times in which using biological factors as mitigating circumstances in a court of law is clearly appropriate. When considering juveniles, for example, their underdeveloped brains need to be taken into consideration. Because children and adolescents do not have fully developed limbic systems, their emotions are often amplified and under-regulated when compared to that of a neurotypical adult (Casey et al., 2008). Further, because of their under developed prefrontal cortex, juveniles tend to make decisions without forethought and have a difficult time with impulse control when compared to a neurotypical adult (Cauffman, 2012). Juveniles are often reformed and treated more easily than adults and yet the United States continues to incarcerate children, sometimes even trying them as adults (MacArthur Foundation, 2015). Ideally, a child’s typical biopsychosocial development should not be halted for the sake of “justice.” Like science, policy making is a dynamic process that changes as time goes on and more information is gathered. As research in biopsychosocial criminology develops, policies will hopefully evolve and improve alongside it.

Future steps for biosocial criminologists

The biopsychosocial perspective is powerful in that it attempts to quantify the biological, psychological and sociology complexities that shape human beings. This earnest attempt to understand the human condition as it relates to crime is often undermined by 20^th century eugenics and beliefs that the field perpetuates biological determinism. To correct these misunderstandings biosocial criminologists should consider the following recommendations. First, biosocial criminology should provide the public with strong, sound research that explicitly confronts racist, ableist, and homophobic concerns. By explicitly stating what our research is not (i.e., not a license to stigmatize or discriminate) we can mitigate the risk of individuals misrepresenting biosocial research and using it to fit their narratives. By familiarizing themselves with the (often problematic) histories and modern-day concerns of the field, biopsychosocial researchers are better positioned to understand the implications of their research. Second, biopsychosocial researchers must make a greater effort to communicate their science to individuals within and outside of the field, at all levels of education and comprehension. Providing the public with a greater understanding of the biological and social risk factors for offending may help foster greater public support for early prevention programs, as well as a more holistic approach to treating offenders and supporting victims. Third, the biopsychosocial perspective goes beyond criminology, making it easier to collaborate with scientists in other fields – we cannot underestimate this privilege. Biopsychosocial criminologists should aim to recruit trainees of diverse educational (i.e., STEM and humanities) and marginalized backgrounds. Cross-disciplinary collaboration furthers advances our understanding of not only crime, but other human behaviors. By bridging the gap between the social/behavioral sciences, the natural sciences and medicine, we are able to better educate students across disciplines. In turn, by working with students with different backgrounds, we enrich the intentions and interpretations of our work.

Conclusion

The goal of this article was to discuss the historical development of biosocial criminology, review key findings and their related policy implications, and discuss broader controversies and future directions for the field. B iosocial criminologists must continue to reckon with the past in order to chart a more purposeful path forward. Research on the biological and social components of crime has uncovered many risk factors associated with crime, but more research needs to be conducted in this area. Our biology affects the way we interact with our environment, and the way the environment interacts with us. For example, someone with “natural” intelligence may be more nurtured in academic settings and may find more success in mainstream school than someone who is perceived to be lazy or inadequate at a young age. Understanding innate differences in how individuals operate within their environments can lead to tailored treatment and intervention programs to curb the development of psychopathology and criminal behavior. Treatment and prevention programs can be informed by findings of biosocial research (Portnoy et al., 2017; Raine et al., 2021) and guided by developmental principles such as neuroplasticity, which peaks in childhood. The new era of biosocial research is contributing to a better understanding of how individual differences and the environment converge to help shape behavior. If used correctly, this improved understanding of human behavior will be crucial in guiding treatment and prevention programs, as well as influencing the criminal legal system, ideally leading to more equitable and just outcomes.

Disclosure statement

No potential conflict of interest was reported by the author.

Notes

1. We use the term “relative” because despite their employment at Harvard, the Gluecks were shunned due to their multidisciplinary training and research approach. Eleanor was treated the most egregiously – employed as a research assistant for over 20 years despite having a doctorate degree (Laub & Sampson, 1991).

2. About 99.9% of humans’ genetic makeup is identical from person to person. When geneticists talk about differences between individuals, they are referring to variations in the ~0.1% portion of the human genome that is expected to be different from person to person (NIH, 2007).