The Persistence of Biological Theories of Crime
Julien Larregue




IN SEPTEMBER OF 2009 at the Court of Appeal in Trieste in Northeast Italy, Abdelmalek Bayout, an Algerian citizen who had been living in the country since 1993, went on trial for murder.1 Two years earlier, in 2007, while in Udine, he had been attacked by a group of young men who made fun of the eye makeup he wore for religious reasons, taunted him with being a homosexual, and eventually knocked him about. To avenge this humiliation, he returned a few hours later and killed one of his assailants with a knife.

In his defense, Bayout’s lawyer asked the court to consider her client’s mental state at the time of the commission of the crime. The trial judge granted her request and ordered a psychiatric examination of the accused. The three reports submitted to the court convinced the judge that Bayout’s mental state did indeed constitute a mitigating factor. The exams had portrayed him as “suffering from a serious psychiatric and psychotic disorder and, in particular, a psychotic delusional disorder accompanied by impulsive-antisocial traits and cognitive-intellectual capacities below normal limits.”2 Nevertheless, the court sentenced Bayout to nine years and two months in prison.

On appeal, during a preparatory hearing held in May of 2009, the appellate judge, Pier Valerio Reinotti, ordered a new psychiatric examination of the convict. Pietro Pietrini, a professor of molecular biology at the University of Pisa, and Giuseppe Sartori, a neuroscientist at the University of Padua, were appointed experts. They conducted a series of tests, including a brain scan and an analysis of genes3 that had been associated with greater aggressiveness in the scientific literature (MAOA, COMT, SCL64, and DRD4). In their report, Pietrini and Sartori stated that they had identified abnormalities in Bayout’s brain imaging as well as in several genes. Their report relied on a study published in the prestigious journal Science in 2002, which had concluded that there was a correlation between a polymorphism of the MAOA gene and the subsequent appearance of antisocial behavior among maltreated children.4 According to the experts, the accused bore a version of the MAOA gene that predisposed its carriers to violence. At the hearing, Pietrini explained that “there is a growing body of scientific evidence that certain genes, when associated with a particular adverse environment, may predispose people to certain behaviors.”5 Pietrini went to emphasize that genes associated with violence produce their deleterious effects only when the individual’s environment is also unfavorable. In other words, the occurrence of antisocial behavior, although linked to the biology of individuals, was not inevitable but statistically probable. On September 18, 2009, the Court of Appeal of Trieste upheld Bayout’s conviction for murder. On the basis of the experts’ reports and the genetic anomaly attributed to the accused, however, the sentence was reduced by one year.

The Trieste case is not an isolated event. It must be understood in a more global context in which crime is biologized, both within the legal sphere and in scientific research. Since the 1950s, the number of scientific publications on the biological factors of crime has grown steadily in criminology, psychology, and behavior genetics. While this revival of the biological conceptualizations of crime has its roots in the second half of the twentieth century, the 2000s have seen the emergence of an unending stream of research devoted to the study of the interactions between biological and environmental factors in the development of criminal behavior. Generally referred to as biosocial criminology, this branch of criminology “incorporates the effects of genetics, physiological and neurological factors, as well as influences of society and family in the causes of antisocial behavior”6 (box 1). Since 2000, dozens of articles in biosocial criminology have been published on the influence that genes, alleles, hormones, heart rate, or neurons might have on deviant conduct. The development of this research movement is such that the historian and criminologist Nicole Rafter has written that “biosociality is likely to become the leading model in 21st-century criminology.”7


Quantitative genetics: Quantitative genetics studies the influence of genetic and environmental factors on human behavior. It includes twin and adoption studies. Research in this area estimates the relative importance of these two factors without, however, identifying the specific genes or environmental conditions involved in the phenomenon under study.

Molecular genetics: Molecular genetics identifies specific genes that are correlated with given behaviors. For example, much research has been carried out on the influence of the MAOA gene mentioned in the Bayout case, including the classic study by Avshalom Caspi and colleagues.8 Other genes that have been associated with criminal behavior in biosocial research include DRD2 and DRD4, DAT1, and 5HTT. The idea of biosocial criminologists is not to identify the “crime gene” per se but to identify risk factors that increase the chances of developing antisocial behavior. These different genes are sometimes grouped together to create a genetic risk index.

Neurocriminology: Neurocriminology aims to identify the neuropsychological factors that favor delinquency. Researchers have examined the correlation between criminal behavior and prenatal and perinatal risk factors such as a mother’s smoking habits, the relationship between the frontal cortex and the caudate nucleus, and the mechanism of self-control.

Biological criminology: Biological criminology is concerned with the role of human physiology in the development of criminal behavior. This branch of research has focused on three main themes: hormones and pubertal development, heart rate rhythms, and blood lead levels.

Evolutionary psychology: Evolutionary psychology applies the Darwinian principle of natural selection to criminal behavior. By tracing human evolution, it seeks to understand the ultimate causes of criminal behavior and answer the more fundamental question of “why.”

As the Bayout trial shows, biosocial criminology has gone beyond the borders of science. Since the 1990s, criminal courts have increasingly resorted to a range of expert assessments based on behavior genetics and neuroscience, the primary aim of which has been to evaluate the criminological dangerousness of offenders in order to assess their chances of reoffending. The importance of this movement is demonstrated by the fact that legal scholars have created a new area of law, sometimes referred to as “neurolaw,” to govern the use of genetic and neurological evidence in criminal proceedings.9 While mainly confined to English-speaking countries, particularly the United States10 and the United Kingdom,11 other legal systems have begun to follow this trend as well: Italy,12 Canada,13 the Netherlands,14 and France,15 which was the first country in the world to pass a bioethics law on this issue.16 Contrary to what one might think, the use of biosocial criminology in courtrooms has not just been initiated by repressive judges. In the United States, defense lawyers have been very actively resorting to neuroscientific and behavior genetic expertise in an attempt to reduce their clients’ criminal responsibility and to avoid the death penalty.17 The results are staggering: in a single decade (2005–15), more than 2,800 judicial opinions discussed neuroscientific evidence in the context of U.S. criminal justice cases.18

Whether repressive or humanistic, the use, actual or potential, of this type of legal expertise raises several questions insofar as biosocial criminology is a recent, still uncertain undertaking. As we shall see, research in this field remains subjected to intense controversies within the scientific community. By examining the historical formation of this criminological specialty and providing a sociological analysis of its scientific results, this book is aimed at providing a critical, reflexive understanding of the stakes at play, both within and beyond the scientific field’s boundaries. How does one proceed to investigate the biological factors of crime? What led to this steady revival of biocriminology, after decades of symbolic discredit? And perhaps more importantly, what credibility can biosocial criminologists justly claim in the face of criticism and skepticism?

Addressing these questions is especially imperative at a time when we are increasingly exposed to a biological culture that purports to discriminate between normal and pathological personhoods.19 Hence, the news of Judge Reinotti’s decision in the Bayout case spread quickly around the world, a fact that can surely be better explained by its sensational appeal and alignment with the bio(ideo)logical framework than by the institutional prestige of the Trieste Court of Appeal. In France, the left-leaning Libération dramatically announced, “An Italian judge discovers the gene for murder”;20 in Great Britain, The Times compared the MAOA gene to a “get out of jail free gene”;21 opting for a somewhat more sober formulation, the Chicago Tribune simply ran the headline “Exploring links between genes, violence, environment.”22

It would be presumptuous, however, to assume that the potential uses of biosocial criminology are strictly limited to the field of criminal justice. In the mid-2000s, an expert group put together by the French National Institute for Health and Medical Research (INSERM) vaunted the reliability of the biosocial approach for the prevention and “treatment” of antisocial behaviors among children and adolescents.23 The publication of the ensuing report gave rise to an intense public controversy.24 An online petition denounced their intervention as an “attempt to instrumentalize care practices in the field of child psychiatry for the purposes of security and public order,”25 while others wondered if scientists promoting genetic screening ran the risk of turning into “police auxiliaries.”26 Aside from the controversies it generated, the INSERM report is also interesting insofar as the proposed prevention program implicated educational personnel and not simply legal institutions. In fact, one of the main recommendations of the expert group was “to improve the current experiments in the prevention of aggressive, antisocial, and delinquent behavior developed in France by adding prevention methods that have been validated at the international level. Following pilot experiments, it [the group of experts] recommends generalizing interventions within existing educational structures (PMI [mother and infant protection], day care centers, schools . . . ) by training educational personnel in these prevention methods (nursery nurses, educators, teachers . . . ).”27

The renewed interest in the biological dimension of delinquent behaviors thus follows a more global movement where numerous social problems are redefined as individual pathologies falling within the purview of a broadly conceived biomedical expertise (cognitive psychology, behavioral genetics, neuroscience, etc.).28 This means that analyzing the development of biosocial criminology entails much more than the single question of delinquency and its management by the criminal justice system. It engages the restructuring of expertise in contemporary societies and the territorial struggles that different professions have engaged in for the monopoly of diagnosis, handling, and treatment of personal problems.29 Indeed, the emergence of biosocial criminology interrogates the division of labor between law and medicine (especially psychiatry) for the control of at-risk populations, an issue that has existed since the nineteenth century.30 As in many professional struggles, scientists, because of their ability to establish on-the-ground realities, that is to impose their own definition (sociological, psychological, biological, etc.) of the nature of a given problem, play a predominant role in this process. For if, as biosocial criminologists suggest, crime is a biological as well as a social problem, then it might demand medical as well as legal solutions, thus putting legal practitioners at risk of losing all or some of their clientele to the health sector.31


1. Feresin, “Lighter Sentence for Murderer”; Musumeci, “New Natural Born Killers?”

2. Court of Appeal of Trieste, cited in Musumeci, “New Natural Born Killers?”

3. It is appropriate at this point to distinguish between DNA samples, which are commonly used by police and criminal justice agencies as evidence to tie an individual to a crime scene or a criminal object (weapons, drugs, etc.), and the behavior genetic tests we are concerned with here. The latter are designed to analyze a person’s genetic makeup to identify factors that might explain his or her actions and allow one to assess future dangerousness.

4. Caspi et al., “Role of Genotype.”

5. Feresin, “Lighter Sentence for Murderer.”

6. Eichelberger and Barnes, “Biosocial Criminology,” 1.

7. Rafter, Criminal Brain, 250.

8. Caspi et al., “Role of Genotype.”

9. Dartigues, “Irrésistible ascension?”; Pickersgill, “Connecting Neuroscience and Law.”

10. Appelbaum, “Law and Psychiatry”; Bernet et al., “Bad Nature, Bad Nurture”; Farahany, “Neuroscience and Behavioral Genetics.”

11. Catley and Claydon, “Use of Neuroscientific Evidence.”

12. Forzano et al., “Italian Appeal Court.”

13. Chandler, “Use of Neuroscientific Evidence.”

14. de Kogel and Westgeest, “Neuroscientific and Behavioral Genetic Information.”

15. Desmoulin-Canselier, “France à ‘l’ère du neurodroit’?”

16. According to the Bioethics Act of July 7, 2011, Article 16-14 of the Civil Code: “Brain imaging techniques may only be used for medical or scientific research purposes, or in the context of judicial expertise. The express consent of the person must be obtained in writing before the examination is carried out, after the person has been duly informed of its nature and purpose. The consent shall mention the purpose of the examination. It may be revoked without form and at any time.”

17. Denno, “Courts’ Increasing Consideration.”

18. Greely and Farahany, “Neuroscience,” 453.

19. Rose, “Normality and Pathology.”

20. Inizan, “Juge italien.”

21. Ahuja, “Get Out of Jail Free Gene.”

22. Tsouderos, “Exploring Links.”

23. Inserm, “Trouble des conduites.”

24. Collectif Pas de zéro de conduite, Pas de zéro de conduite.

25. Collectif Pas de zéro de conduite, “Le texte de l’appel ‘Pas de zéro de conduite pour les enfants de trois ans,’ March 10, 2006, no longer accessible online, accessed February 4, 2020.

26. Cartuyvels, “Troubles de conduite,” 62.

27. Inserm, “Trouble des conduites,” 377.

28. Conrad, Medicalization of Society; Morel, Médicalisation de l’échec scolaire; Richardson, Maternal Imprint; Rose and Abi-Rached, Neuro; Rollins, Conviction.

29. Abbott, System of Professions, 280–314.

30. Foucault, Surveiller et punir; Kaluszynski, “Identités professionnelles, identités politiques.”

31. Larregue, “Nouvelle orange mécanique.”