Scholars have long attempted to identify the biological determinants of crime and violence. Indeed, the historical record indicates that many of the earliest criminologists – including Cesare Lombroso (1835–1909), Raffaele Garofalo (1852–1934) and Enrico Ferri (1856–1929) – believed that certain physical characteristics indicated a “criminal nature” (see discussions in Englander, 2007; Siegel and McCormick, 2006; Ellis, 2005; Fishbein, 2001; Paternoster and Bachman, 2001).
Lombroso’s manuscript L'Uomo Delinquente (The Criminal Man) is perhaps the most famous of these early efforts to draw a direct link between biology and crime (Lombroso, 1876). A professor of medicine at the University of Turin, Lombroso conducted his research in the Italian prison system. As part of his work, he collected detailed anatomical measurements of prisoners and compared them with measurements taken from “ordinary” Italian citizens. According to Lombroso, criminals possessed certain physical characteristics (including long arms and fingers, sharp teeth, abnormal amounts of body hair, extended jaws, etc.) that distinguished them from ordinary citizens. In sum, he argued that criminals were atavists – biological throwbacks to an earlier period of human evolution. He further maintained that these atavists engaged in criminal activity, including violence, because it was instinctive for them to do so. Finally, because they are the product of biological forces, Lombroso felt that criminals lack free will and are thus not morally responsible for their actions.
The work of Lombroso and his contemporaries was largely discounted by modern criminologists. To begin with, many of these early studies were based on small, nonrandom samples and rarely involved adequate control groups. Furthermore, many of the physical traits that these scholars assumed to be genetically determined could have been caused by deprived social conditions, including poor nutrition and health care. Lombroso also failed to consider the many social factors that could lead to criminality. Thus, after being dismissed as methodologically unsound and naive, biocriminology fell out of favour during the early 20th century. During this period, scholars turned their attention to more sociological explanations of criminal behaviour (discussed below).
An interest in the biological correlates of crime, however, was rekindled in 1970s after the publication of Edmund O. Wilson’s book entitled Sociobiology. Wilson (1975) argued that people are biosocial organisms whose behaviours are influenced by both their physical characteristics and the environmental conditions they are faced with. Rather than viewing criminals as people whose behaviours are totally controlled or predetermined by their biological traits, modern biosocial theorists believe that physical, environmental, and social conditions interact in complex ways to produce human behaviour (see Englander, 2007; Ellis, 2005; Fishbein, 2001; Yaralian and Raine, 2001). Biosocial thinkers ask a basic question: When faced with the same environmental stressors, why do some people engage in violence while most people do not? They further maintain that certain biological abnormalities or physical disabilities may make some individuals more prone to violence or aggression than others. The perspective of many sociobiologists was captured by van den Bergle (1974: 779):
What seems no longer tenable at this juncture is any theory of human behaviour which ignores biology and relies exclusively on sociocultural learning. Most scientists have been wrong in their dogmatic rejection and blissful ignorance of the biological parameters of our behaviour
The following sections briefly outline some of the important topics within the bio-criminological tradition. First we will review the biochemical factors believed to affect behaviour. Then we will discuss the alleged relationship between brain function and violence, followed by a discussion of the possible link between genetics and crime. Finally, we will briefly review evolutionary views regarding crime causation.
Some biosocial theorists believe that biochemical conditions – including those acquired through diet – can control or influence violent behaviour. Biochemical factors that might influence aggression range from nutrition to allergies.
Biocriminologists maintain that minimum levels of vitamins and minerals are required for normal brain functioning. Medical research suggests that proper nutrition is especially important during early childhood. Nutritional deficiencies at this stage in child development can result in serious physical, mental and behavioural problems (Liu and Wuerker, 2005; Neisser et al., 1996). Research also suggests that improving diet quality can reduce delinquency and dramatically improve the mental functioning and the academic performance of adolescents (see Schoenthaler and Bier, 2000). Other studies indicate that deficiencies in potassium, calcium, amino acids, sodium, peptides, and other nutrients can lead to depression, mania, and cognitive problems. Such mental health issues can, in turn, significantly increase the probability of violent behaviour. Similarly, studies have found a strong link between anti-social behaviour and insufficient quantities of vitamins B3, B6 and C (Siegel and McCormick, 2006; Liu and Wuerker, 2005; Krassner, 1986).
Diets high in sugar and carbohydrates have also been linked to violence, aggression and other behavioural issues (Gans, 1991). One experiment with incarcerated youths, for example, found that reducing sweet foods and drinks in the prison diet produced a 45 per cent decline in institutional violence (Schoenthaler and Doraz, 1983). However, more recent studies suggest that most people with high sugar/carbohydrate diets never engage in serious violence and that, for some individuals, sugar actually has a calming effect that reduces aggression (Gray, 1986; Wolraich et al., 1994).
Other studies indicate that how the brain metabolizes glucose may determine whether sugar causes anti-social behaviour. Hypoglycemia, for example, is a condition that causes glucose to fall below the level needed to maintain normal brain functioning (the brain is the only organ that obtains all of its energy from glucose). Symptoms of hypoglycemia include anxiety, depression, insomnia, nervousness, mood swings, phobias and temper tantrums. A number of important studies have found a significant relationship between hypoglycemia and violence – including assault, homicide and rape. Furthermore, studies of prison populations have found higher than normal rates of hypoglycemia among habitually violent inmates (Seigel and McCormick, 2006; Virkkunen, 1986).
In his manuscript entitled The Moral Sense, renowned criminologist James Q. Wilson argues that hormones and neurotransmitters may explain gender differences in violent behaviour. He maintains that gender differences in exposure to androgens (male sex hormones) explain why males are naturally more violent than females and why females are more nurturing and empathetic (Wilson, 1993). Hormone levels have also been purported to explain the aging out of violence. In other words, some scholars feel that the decrease in violent behaviour with age is directly related to age-related declines in androgen levels. Many have observed that both violence and androgen production in males peak during adolescence (Gove, 1985; Booth and Osgoode, 1993; Piquero and Brezina, 2001). Others have argued that artificially increasing the level of male hormone within the body – through steroid use – can contribute to explosive episodes of violence, often referred to as “roid rage” Recent studies have provided limited support for this hypothesis (see Pedersen et al., 2001; Isacsson et al., 1998).
A number of biosocial theorists are currently exploring the relationship between hormone levels and violent behaviour. Indeed, several studies have produced findings that suggest that abnormally high androgen levels are, in fact, correlated with aggressive behaviour (see Ellis, 2005; Raine, 2002; Fishbein, 2001; Rappaport and Thomas, 2004). Testosterone is the most abundant androgen. Research suggests that prenatal exposure to high levels of testosterone – sometimes as a result of medical intervention – can sometimes result in higher levels of aggression in female children. By contrast, during fetal development, males who are exposed to drugs that lower androgen levels display lower levels of aggression through childhood and adolescence (see Reiss and Roth, 1993). Studies of inmate populations have also found that testosterone levels are significantly higher among offenders convicted of violent offences than among those convicted of property crimes (Kreuz and Rose, 1972).
In a thorough meta-analysis of the research literature, researchers from Queen’s University in Ontario found a small but statistically significant relationship between testosterone levels and violence. However, this study also found that the influence of androgens varies dramatically from study to study and from culture to culture. Furthermore, researchers have yet to determine causality. For example, although some argue that testosterone levels cause violence, new evidence suggests that engaging in or observing violent behaviour can actually cause a dramatic increase in testosterone levels (see Book et al., 2001).
High testosterone levels are thought to increase the probability of violent behaviour in three distinct ways. First of all, the presence of male sex hormone is thought to decrease an individual’s sensitivity to adverse environmental stimuli. Those with high testosterone levels are thus more likely to take risks, more likely to seek excess stimulation and more capable of tolerating pain in their quest for thrills. Secondly, androgens are also linked to brain seizures that, under stressful situations, can result in emotional volatility. Finally, androgen exposure causes neocortical functioning to be less concentrated in the left hemisphere of the brain. The left hemisphere of the neocortex, of course, is the part of the brain that determines sympathetic feelings for others. Thus, these three factors, alone or in combination, may help explain the apparent relationship between male hormone levels and violent behaviour (Ellis, 2005).
It must be stressed that androgens are not the only hormonal risk factor associated with violent behaviour. It has long been suspected, for example, that the onset of the menstrual cycle often triggers the release of excessive amounts of female sex hormones (estrogen and progesterone). This rise in female hormone levels may, in turn, contribute to an increase in anti-social behaviour. This phenomenon is commonly known as Premenstrual Syndrome (PMS). The possible link between PMS and violence was first documented in England, where studies identified that women were more likely to commit suicide or engage in other aggressive behaviours just before or during menstruation (see Dalton, 1971; Horney, 1978). More recently, Diana Fishbein, a leading biocriminologist, documented that a disproportionate number of incarcerated females committed their crimes during the premenstrual phase (see Fishbein, 2001; Fishbein, 1996).
In sum, although some research suggests that there may be a moderately strong relationship between hormone levels and violence, criminologists remain cautious about the explanatory power of this correlation. After all, the vast majority of males with high testosterone levels never engage in serious violence. Likewise, the overwhelming majority of women experience their menstruation cycle every month and never engage in aggressive behaviour. Future research, therefore, must better identify under what circumstances hormonal levels may increase the probability of violent behaviour.
Allergies refer to reactions of the body to foreign substances (Seigel and McCormick, 2006). Cerebral allergies cause a reaction in the brain. Neuroallergies affect the nervous system. Both cerebral allergies and neuroallergies have been linked to mental, emotional, and behavioural problems. A growing body of research suggests that there is also a link between allergies and depression, hyperactivity, aggressiveness, and violence (Liu and Wuerker, 2005; Raine, 2002; Marshall, 1993). Most cerebral allergies and neuroallergies are caused by exposure to certain types of food – including milk, wheat, eggs, nuts and chocolate. Corn, for example, is a suspected cerebral allergen that has been linked to countries with higher than average homicide rates (Mawson and Jacobs, 1978). The argument is not that allergies directly cause violence. Rather, those suffering from the stress of a painful allergic reaction may be more likely to act violently when presented with negative stimuli.
Sociobiological scholars have also drawn a connection between exposure to dangerous contaminants – including copper, mercury, chlorine, artificial colouring, food dyes, etc. – and both aggressive and anti-social behaviour (see Rappaport, 2004; Ellis, 2005). A great deal of recent research has focused on the possible relationship between lead poisoning and violence. One study, for example, found that communities with the highest concentrations of lead in the air also reported the highest levels of homicide and other forms of violence (Stretesky and Lynch, 2001). A number of studies have also found that lead poisoning is one of the most significant predictors of male delinquency and persistent adult criminality (see Denno, 1996; McCall and Land, 2004). Needleman (1996), for example, tracked several hundred boys from ages seven through eleven and found that those with high concentrations of lead in their bones were much more likely to demonstrate attention deficit problems, poor language skills, delinquency, and aggression. High lead ingestion is also linked to lower IQ scores – a factor that can contribute to youth violence (Neisser et al., 1996).
Some academics believe that neurological and physical abnormalities acquired early in life – even as early as the fetal stage – impact behaviour throughout the lifespan (see Arseneault et al., 2000; Moffit et al., 1994; Moffit, 1990). Particular focus has been placed on how the impairment of basic brain functions (abstract reasoning, problem-solving skills, motor skills, etc.) may increase the probability of criminal and violent behaviour.
One of the most important measures of normal neurological functioning is the electroencephalograph (EEG). An EEG refers to the electrical impulses given off by brain waves. These impulses can be recorded by electrodes placed on the scalp (Seigel and McCormick, 2006: 165). Several studies have found that violent criminals – including murderers – have much higher EEG recordings than non-violent criminals have (see review in Rowe, 2001). Furthermore, studies suggest that 50 to 60 per cent of habitually violent adolescents have abnormal EEG readings, compared with only five to fifteen per cent of the general population (Rowe, 2001). Research also suggests that psychiatric patients with EEG abnormalities are highly combative and frequently suffer from periodic manifestations of extreme rage (Rowe, 2001). In some studies, researchers using brainwave data have predicted within 95 per cent accuracy the recidivism of violent offenders (see Yaralian and Raine, 2001). In sum, EEG analysis demonstrates that measures of abnormal brain activity are significantly associated with anti-social and violent behaviour. The exact reason for this association, however, has yet to be discovered.
Fetal Alcohol Syndrome (FAS) develops when fetuses are exposed to high levels of alcohol in the womb. These children subsequently demonstrate developmental delays and deviant behaviour – including violence. Common cognitive problems associated with FAS include learning difficulties, poor impulse control, a need for immediate gratification, speech problems and the inability to consider the long-term consequences of one’s actions. Research also suggests that a high proportion of FAS children ultimately demonstrate aggressive behaviour (see review in Fishbein, 2001).
It is estimated that only one per cent of all children are born with Fetal Alcohol Syndrome. However, studies also suggest that between 40 and 80 per cent of all children in foster care are stricken with this disability. Studies also estimate that at least half of all young offenders who appear in provincial or territorial courts had mothers who drank heavily during pregnancy (Gideon et al., 2003).
Minimal Brain Dysfunction (MBD) is related to abnormalities in cerebral structure. In its most serious form, MDB is associated with severe anti-social behaviour, including hyperactivity, poor attention span, temper tantrums and aggressiveness. MDB has also been linked to episodes of explosive rage and has often been viewed as a significant predictor of both suicide and motiveless homicide. Some studies have found that up to 60 per cent of prison inmates exhibit symptoms of Minimal Brain Dysfunction (Seigel and McCormick, 2006; Monroe, 1978).
Medical estimates suggest that between three and five per cent of children, most often males, suffer from Attention Deficit/Hyperactivity Disorder (AD/HD). In fact, AD/HD is the most common reason that children are referred to mental health clinics. The suspected causes of this disability include neurological damage, prenatal stress, food allergies and genetics. Research has also found a strong relationship between AD/HD and poor school performance, bullying, and a lack of response to punishment (Faraone, 1993). There is also a strong association between AD/HD and the early onset of chronic delinquency and persistent violent behaviour (Weiss and Murray, 2003; Moffit and Silva, 1988; Hart et al., 1994).
Brain tumours have been linked to severe psychological problems, including hallucinations and psychotic episodes. People with brain tumours are more vulnerable to depression, irritability, temper tantrums and homicidal behaviour. Furthermore, research suggests that normally calm, peaceful individuals can become extremely violent after developing a tumour. When tumours are removed, however, normal behaviour patterns can resume. Studies also indicate that head injuries caused by accidents can dramatically increase violent behaviour and aggressiveness among normally passive individuals (Ellis, 2005). One study of Montreal youth also found that fetal brain damage greatly increased the risk of violence in boys once they reached 16 and 17 years of age (Tremblay et al., 2002). Finally, a wide variety of central nervous system diseases – including epilepsy, cerebral arteriosclerosis, senile dementia and Huntington’s chorea – can also lead to affective disturbances, including episodes of rage and anger (Fishbein, 2001; Rowe, 2001).
Neurotransmitters are chemical compounds that influence brain activity. Research suggests that abnormal levels of some neurotransmitters – including dopamine, serotonin, and monoamine oxidase – are related to aggression and violence. For example, people with a history of impulsive violence often have a reduction in the function of the serotonin system (Badaway, 2003). Studies of habitually violent Finnish offenders, for example, show that low serotonin levels are related to hyperactivity and aggression (Virkkunen et al., 1989). Research also suggests that individuals with a low supply of monoamine oxidase (MAO) are more likely to engage in sensation-seeking activities – including violent behaviour. It is interesting to note that females generally have much higher levels of MAO than males do, a fact that could help explain gender differences in aggression (Huizinga et al., 2006; Ellis, 1991).
According to Arousal Theory, peoples’ brains function differently in response to environmental input. In general, people attempt to maintain an optimal level of arousal. Too much stimulation causes anxiety and fear, while too little stimulation leads to boredom and depression. However, individuals also differ dramatically with respect to their cognitive ability to process environmental stimuli. In other words, some people feel comfortable with very little stimulation, while others require a high level of environmental input. These “sensation-seekers” or “thrill-seekers” are much more likely to engage in a wide variety of risky activities – including violent behaviour. Unfortunately, all the factors that determine an individual’s optimal level of arousal have not yet been determined. Possible sources include brain chemistry (including serotonin levels) and brain structure (see reviews in Raine et al., 1997; Ellis, 2005; Fishbein, 2001; Ellis, 1996).
The first criminologists, including Lombroso, often believed that anti-social behaviour had a genetic basis. In other words, they believed that some people are “born criminals.” As discussed above, this early work has been thoroughly discredited by enlightened thinkers. In the 1960s, however, the debate over genetics and violence emerged once again. Much of this revival centred on the famous “XYY” controversy. XY is the normal chromosomal pattern for males. However, some males in the general population have an extra Y chromosome. Many came to believe that these XYY males were much more aggressive than “normal” males and often engaged in serious violence – including homicide. This led to suggestions that XYY males should be identified at birth and thoroughly monitored by the state in order to prevent violence. However, research eventually found that most violent offenders – including the majority of serial killers – did not have an extra Y chromosome. Interest in XYY theory subsequently diminished (Sarbin and Miller, 1970). Nonetheless, a number of contemporary scholars remain highly interested in genetics. Some biosocial theorists, for example, have gone so far as to state that certain violent personality traits – including psychopathy – may be inherited (Carey and DiLalla, 1994).
Twin studies have become one of the most popular methods for examining a possible genetic basis for aggression. If inherited traits actually cause behaviour, twins should be quite similar in their propensity for violence. However, since twins are most often brought up in the same social environment, determining whether their behaviour is the product of biology or social conditions is quite difficult to determine. Researchers have tried to overcome this obstacle by comparing identical (MZ) twins with fraternal (DZ) twins of the same gender. MZ twins are genetically identical, while fraternal twins only share half their genes. Thus, if genes actually impact aggression, identical twins should be more similar in their violent behaviour than fraternal twins are. A number of studies have produced findings that are consistent with this hypothesis (Seigel and McCormick, 2006; Rowe, 1986). Mednick and Christiansen (1977), for example, studied over 3,000 twin pairs and found a 52 per cent correspondence in the aggressive behaviour of identical twins, compared with a correspondence rate of only 22 per cent for fraternal twins. Other researchers have concluded that people who share genes also share similar personality traits, regardless of the social environment in which they were raised (100). This has led some biosocial experts to conclude that identical twins may share genetic characteristics that increase – or decrease – their probability of engaging in violent and/or criminal behaviour (see Rowe, 1995).
Other studies, however, have found very little evidence that identical twins are more similar in criminal behaviour than fraternal twins or non-twin siblings are. The authors of these reports maintain that siblings often share similar social environments and that it is the social environment, not genes, that produces similarities in violent behaviour (Carey, 1992). Contagion theory, for example, holds that siblings, especially twins, often behave in a similar fashion because they are raised in the same families and are exposed to the same social and economic conditions. Furthermore, most siblings, especially twins, develop a close emotional relationship and frequently develop similar interests. Thus, because of their emotional closeness, twins are more likely to influence each other’s behaviours than other siblings are. This hypothesis is also supported by research that suggests that identical twins behave more similarly in early childhood and as adults than they do during adolescence. During adolescence, youth often try to break away from the family and establish their own identities. This explains why, during the teenage years, youth are more influenced by their peers than by family members (Jones and Jones, 2000; Fishbein, 2001).
Nonetheless, support for a genetic explanation for violence has also received some support from adoption studies. Logic holds that genetic explanations for crime would be supported when a young person’s behaviour is more similar to that of the biological parents than it is to that of the adoptive parents. On the other hand, social explanations would be supported when a young person’s behaviour is more similar to that of the adoptive parents than it is to that of the biological parents. A number of European studies have found that the criminality of biological parents is a significant predictor of youth violence, even after controlling for the behaviour of adoptive parents and other environmental variables. However, the evidence also suggests that the social environment found in the adoptive home has a very significant impact. For example, rates of violence are lowest when both biological and adoptive parents are non-violent. However, rates of violence among adopted youth increase when either the biological or the adoptive parents have histories of violent behaviour. Finally, the highest levels of violence among adopted children are produced when both the biological and adoptive parents have a criminal past (Walters, 1992). Such findings indicate that genetic and social conditions may interact in complex ways to either increase or decrease the probability of violence and criminal behaviour.
The final biosocial theory to consider is based on ideas about human evolution. Experts in this field argue that, as human beings evolved, certain traits, emotions and characteristics became genetically ingrained. Jealousy, for example, is a human emotion that may have evolved in order to keep families together and increase the probability of reproduction (see Seigel and McCormick, 2006).
Evolutionary theory has most often been used to explain gender differences in both violent behaviour and sexual activity. According to some evolutionary theorists, in order to ensure their genetic legacy, it is advantageous for males to mate with as many females as possible. On the other hand, because of the physical toll of a long gestation period, it is advantageous for females to mate with only a few males – especially those who are thought to be nurturing or carry the best genetic material. Because of these different mating strategies, it has been argued that the most aggressive males have historically been able to mate with the largest number of women. From an evolutionary perspective, violence is thought to have developed as a male reproductive strategy because it can: 1) eliminate or deter genetic competition (i.e., prevent rival males from getting the opportunity to mate); 2) serve as a method for displaying physical strength (genetic superiority) and attracting females; and 3) deter females from leaving and mating with other males. In our distant past, therefore, male aggression may have frequently led to reproductive success. If so, aggressive traits would be more likely than passive traits to be passed on to the next generation of males. Thus, it is often assumed by biosocial experts that the descendants of aggressive males account for the fact that, even in modern society, men continue to be more violent than women (Ellis and Walsh, 1997).
It should be noted that other much more theoretically complex versions of evolutionary theory have emerged in recent years (see Seigel and McCormick, 2006, for example, for a detailed discussion of R/K Selection Theory and Cheater Theory). Nonetheless, at the core of all evolutionary theories is the idea that violent, aggressive behaviour has been maintained within human cultures because it has proven to be a successful reproductive strategy – especially for males.
Biosocial theorists face a number of serious criticisms (Englander, 2007; Walters and White, 1989; Ellis, 2005; Fishbein, 2001; Seigel and McCormick, 2006). First of all, biosocial research is often fraught with methodological problems. Many studies, for example, are based on small, unrepresentative samples and do not adequately control for the impact of social variables. Biosocial theories also fail to explain regional and temporal differences in violent crime rates. For example, biosocial theories cannot begin to address why the Western Canadian provinces have much higher homicide rates than the Eastern provinces. Nor can they address why the United States has a much higher rate of violent crime than that of Canada or most European countries. Furthermore, biosocial theories cannot totally account for changes in violent behaviour over time. For example, in North America, the violent crime rate increased significantly between the 1950s and 1990s. Starting in the 1990s, however, the violent crime rate began to decline. How can sociobiological theories – by themselves – account for such significant geographical and longitudinal changes? Are people in British Columbia genetically different from people in Nova Scotia? Did the basic biological makeup of human beings change between the 1990s and the 1950s?
Some biosocial criminologists have also been accused of racial and class bias (Roberts and Gabor, 1990). If, for example, biology can explain violent crime, and poor people and racial minorities commit a disproportionate number of violent acts, then by implication these types of people are inherently inferior or flawed. Critics argue that it would be much more productive – and empirically accurate – to focus on the social factors (oppression, racism, social exclusion, economic strain, etc.) that produce racial and class differences in violent behaviour than to spend our efforts trying to uncover the genetic basis for criminality. Such scholars, however, warn that biosocial theories may be attractive to some because they can be used to justify social inequality and deflect attention from crime prevention efforts that might challenge the status quo.
A number of biologically based medical treatments or interventions have been used to treat violent offenders (see Englander, 2007; Ellis, 2005). Prevention programs, for example, have sometimes focused on improving the diets of at-risk youth. Other initiatives have treated specific allergies. Neurosurgery has also been used to remove brain tumours and correct abnormal neurophysiological conditions associated with aggression. However, the most common strategies for dealing with the biological determinants of violent behaviour involve the administration of prescription drugs. Drugs that decrease testosterone levels or increase levels of female sex hormones, for example, have been used to treat violent sexual offenders. Chemical castration has also been used in the United States to diminish the threats posed by chronic pedophiles. Similarly, the most common treatment for AD/HD involves the administration of stimulants – including Ritalin and Dexedrine – that help control emotional or violent episodes. Violence-prone individuals have also been treated with anti-psychotic drugs that help control neurotransmitter levels. Finally, narcotics are sometimes used to produce an elevated mood state in those with high arousal levels.
A number of criminologists maintain that biologically oriented treatments are the best strategy for dealing with chronic, lifetime-persistent offenders. To support their argument, they often point to the fact that, once their genetic codes were broken, a number of inherited traits that cause disease have been successfully treated with medication. Can the same types of solutions, they ask, be used to deal with violence? The potential of a genes-violence relationship is by far the most controversial issue facing biosocial criminologists. After all, such a relationship would suggest that violent propensities are present at birth and cannot be altered. It thus raises a number of important moral issues. For example, if genetic testing could identify a “violence gene,” should fetuses with this gene be aborted? Similarly, if we can identify biological markers that increase the risk of violence, should individuals with these traits be subject to greater surveillance by the criminal justice system? Fortunately, these are not issues we have to deal with in this report. Biosocial theorists are nowhere close to proving a genetic basis for crime – and many criminologists believe they never will be.
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