This doctoral thesis deals with the role of neuroscience in criminal law. It begins with a brief introduction to the scientific field of neuroscience. Although there is no single definition of neuroscience, the discipline does, however, have a common object of research – the functioning of the brain and the nervous system. The most salient and constitutive feature in the field of neuroscience is its multitude of interdisciplinary research approaches. Some of the most widely used modern methods to exploring the brain are presented and compared. After the difference between structural and functional brain imaging methods is explained, the following methods are further outlined and compared: computed tomography (CT, also known as computed axial tomography – CAT), magnetic resonance imaging (MRI), positron emission tomography (PET), single-photon emission computed tomography (SPECT), and functional magnetic resonance imaging (fMRI). Electroencephalography (EEG) is added to these as an equally prominent non-imaging method.
The dissertation firstly touches upon the overlapping areas of neuroscience and criminal law by reviewing and evaluating the body of research dealing with the persuasiveness of neuroscience. It has been established both in legal and non-legal contexts that explanations of psychological and behavioural phenomena fare much better in terms of their credibility when based on neuroscience (or even just using redundant neuroscience jargon). However, research has not been able to confirm the so-called seductive allure of brain imaging evidence. Therefore, the initial proposition that judicial decision-makers deem brain images far more convincing and persuasive than other comparable evidence has not been confirmed.
The interface between neuroscience and criminal law is further explored by reviewing the few existing empirical studies on the role of neuroscience in criminal courts in four different countries, namely the United States, England and Wales, Canada, and the Netherlands. Despite some notable differences between the countries, this area of research shows that the use of neuroscience-based evidence has increased in criminal trials around the world; it has been present in criminal procedures for all types of crime, but more prevalent with serious, violent crime. Its impact on judicial decisions has been significant, most evidently in the sentencing phase of the common-law jurisdictions. Notwithstanding that in courts of law the introduction of neuroscience evidence typically turns the outcome of the trial (to greater or lesser extent) to the defendant’s advantage, there are reported cases where such evidence had just the opposite effect, and was used to establish defendant’s greater risk for reoffending. This phenomena has been dubbed as the double-edged sword of neuroscience.
The empirical core of this doctoral thesis consists of two studies on the impact of neuroscience in the Slovenian criminal justice system. The first, preliminary one, drew from a publicly available database containing (many but not all issued) second- and third-instance court decisions. Among other findings this study showed that neuroscience evidence had been employed at trials for a wide and diverse spectre of criminal offences. Surprisingly, these did not only encompass crimes but also a substantial proportion of misdemeanours. However, as in other reviewed jurisdictions, in Slovenia, too, neuroscience evidence is most often used in homicide trials.
Therefore, the second study focused on homicide cases in particular and strived to overcome some of the drawbacks of previous empirical research in this field. To the knowledge of the author, this is the first empirical study in any civil or common-law jurisdiction systematically searching for neuroscience evidence in all adjudicated cases of a particular type of crime. Thus, all written judgments for charges of homicide (murder and manslaughter) that became final from 1991 to 2015 in Slovenia (495 cases) have been analysed. These include first-instance and (when issued) appellate as well as Supreme Court decisions directly obtained from all the Slovenian district courts. By combining qualitative and quantitative research methods it was possible to assess the nature and the role of neuroscience evidence and its impact on final judicial decisions in homicide trials in Slovenia.
Results have shown that 18 % of all Slovenian homicide trials in the past 25-year period involved neuroscience-based evidence pertaining to defendant’s brains. In light of some rare comparable estimations, the prevalence of neuroscience in Slovenian courts appears relatively high. However, contrary to all other research, the research has not revealed an increase in the number of cases involving neuro-evidence in recent years. Results show that the information about defendants’ brains has a significant effect on judicial decisions. This does not reflect only in the sentencing phase, as is the case in the common-law jurisdictions, but as early as in courts’ considerations of defendants’ criminal capacity. These findings are similar to the only existing civil-law study conducted in the Netherlands suggesting that the use of neuroscience in civil-law criminal jurisdictions is different to that in common-law legal systems. Finally, the presented research has not been able to confirm the double-edged sword of neuroscience in Slovenia.
Next chapter revolves around the substantive criminal law issues and the impact that the contemporary findings about the functioning of human brain have in this theoretical field. The chapter opens with a brief discussion about the problem of free will and the contribution that modern neuroscience can offer to this debate. Although this issue is still far from resolved, a number of examples are drawn from neuroscience indicating that human decisions are more neurologically determined and less rational than traditional criminal law is willing to acknowledge. By confronting both views on free will, the one adopted by criminal law and the neuroscientific one, several possible solutions come to the fore. First, it is clear that criminal law cannot and does not need to abandon the notion of free will. But it can, nevertheless, accommodate recent discoveries about the neurological influences on human behaviour. This dissertation claims that this has in fact already been done in many jurisdictions in the area of juvenile criminal law. For example, a number of criminal justice systems around the world have started treating young adults less severely (similarly to adolescents) by openly quoting well-established findings about neurodevelopmental specifics in the brains of young adults influencing their behaviour.
In the following passages, some more specific substantive criminal law issues are tackled. Neuroscience is found to be useful in distinguishing between situations when it is not clear whether the defendant can claim the so-called izključenost kazesnkopravnega ravnanja, an analogues defence to common-law automatism defence, or insanity (neprištevnost). Indeed, modern neuroscience proves to be most valuable in courts’ evaluations of defendant’s criminal capacity. The science of the brain can readily identify the roots of the biological component of the defendant’s alleged insanity or substantially diminished capacity (bistveno zmanjšana prištevnost). But this in turn amounts to a longer causal link that needs to be established between a certain neurological condition, biological element, and, finally, psychological element of insanity. Mutatis mutandis, the same can be applied to the process of proving a defendant’s fitness to stand trial. Furthermore, neuroscience methods have proven to be an ineffective tool when it comes to the relatively common and consequential question of delimitation between insanity and its less severe form, substantially diminished capacity. Hope has been induced by recent functional neuroimaging studies proving that novel neuroimaging approaches would be able to assist judges in determining the appropriate form of defendant’s guilt (e.g. knowledge (eventualni naklep) or negligence (nezavestna malomarnost)). But this scenario seems extremely unlikely as perpetrator’s subjective attitude towards a criminal act is typically neither sufficiently reflected for nor identical with normative categories of guilt prescribed by law.
In the field of substantive criminal law neuroscience, nevertheless, has a strong impact on criminal sanctions. In Slovenian criminal justice system, this is evident both in sentences as well as safety measures. By producing neuroscience-based evidence, an argument can be made for the use of mitigating circumstances or even a reduction of sentence below the statutory minimum prescribed by the Criminal Code for a particular crime. Perhaps the contribution of neuroscience is even a greater when it offers a prediction of a defendant’s future behaviour. This assessment can be of an invaluable assistance to the court when deciding whether safety measures of involuntary psychiatric treatment in a health institution or involuntary psychiatric treatment at liberty should be ordered. The court imposes these measures when an insane perpetrator or one with substantially diminished mental capacity is deemed dangerous and likely to reoffend.
In contrast to the section of the thesis dealing with questions of substantive criminal law recognising many opportunities for neuroscience, the following chapter, tackling procedural criminal law issues, identifies the main hindrances for the use of neuroscience in this legal discipline. These impediments show mostly (but not exclusively) in the form of defendant’s fundamental rights, procedural safeguards, and a right to a fair trial. Before immersing into purely legal arguments against the use of certain neuroscience-based methods in criminal law, the question of probative value of this evidence is explored.
Structural brain imaging are less ambiguous and therefore less disputable as other types of analysed evidence. But nevertheless, the consequences of abnormalities revealed by structural brain images are to a great extent open to interpretation and in this sense arguable. In terms of the taxonomy of the Slovenian Criminal Procedure Act (ZKP), structural brain imaging can be deemed either as a type of medical proceedings similar to physical examination (Article 266, Paragraph 2) or a part of psychiatric examination (Article 265); in both cases a person can be subjected to structural brain imaging even without her consent.
Compared to structural neuroimaging proving with functional brain images in a court of law is even trickier. These methods are susceptible to many methodological pitfalls and interpretational ambiguities. This demands great cautiousness in the use of functional brain images in criminal procedures. Another distinct but related category of evidence are fMRI- and EEG-based techniques searching for content in subjects’ minds. This thesis mostly centres on deception-detection and memory-recognition methods (the latter approach using EEG technology is often termed as brain fingerprinting). It is the position of this dissertation that despite some very promising results the presented methods have not yet reached validity and reliability justifying their application to the criminal justice system. It is surprising that despite the same consensus both among legal scholars and neuroscientists these methods have already been used in criminal courts in a number of countries (most notably in India and to a lesser extent in the United States).
However, even greater obstacles for the use of brain fingerprinting and fMRI-based lie detection methods as discovered by this thesis are of a legal nature. The first objection pertains to the privilege against self-incrimination and the right to silence. Despite the initial dilemma whether this evidence is testimonial or material in nature and therefore whether it is even protected by the privilege in the first place, this thesis stands on the position that this dilemma is false and that all such evidence is indeed testimonial. This stance is grounded in the state’s intention to use this approach to access the content of the defendant’s mind not to recognise the biological properties of her brain. Thus, neuroscience-based technologies are only a tool to circumvent a defendant’s will to testify. Moreover, it is the conclusion of this dissertation that these approaches cannot be used even with witnesses, which are not protected by the privilege, or should the defendant renounce her privilege. Such techniques would directly contradict the prohibition of the application of medical procedures and agents influencing one’s will to testify provided by the Slovenian Criminal Procedure Act in Article 266, Paragraph 3.
An additional argument against the use of the discussed techniques can be drawn from the principles of cognitive freedom and mental privacy. The concept of mental privacy is relatively young and therefore theoretically not yet fully developed. In this dissertation it is defined as a right protecting all qualitatively subjective information from a person’s mental sphere over which a person can exercise an autonomous and independent decision whether or not she will share them with others. It covers one’s thoughts, perceptions, memories, emotions, and other subjective attitudes towards the world. Notwithstanding that explicit mentioning of mental privacy cannot be found in any legislation, it can be derived from the constitutionally protected general right to privacy and personality rights (Articele 35 of the Constitution) in conjunction with the concept of reasonable expectation of privacy as well as the established functional conception of privacy.
The final question, stemming from all the presented findings about the collision of neuroscience-based interrogation methods with various rights, is whether these rights are absolute. In other words, can one validly consent to these techniques and renounce her rights to mental privacy and privilege against self-incrimination? Similarly, should these right in certain circumstances, even against the will of the subjected person, give way to some more important interests in criminal procedure? This dissertation replies negatively to both these questions. It supports its position with the meta-argument of the protection of human dignity and personality in criminal procedure. A criminal justice system not recognising the seat of a human personality and autonomy in one’s brain, and instead seeing it only as a source of evidence that can and should be decoded in order to further a criminal trial, objectifies a person and denies her human dignity and personality.
The last chapter of the dissertation tackles the dilemmas when, if at all, is it permissible to change the brains of people convicted of crimes. This discussion is sparked by a number of existing practises in which convicts (especially those convicted for sexual crimes) are subjected to rehabilitative therapies and programmes changing their behaviour and their brains. While a number of non-contested methods, such as cognitive-behavioural therapies, have been a part of criminal justice systems for a long time, lately more controversial methods are coming to the fore. These include various types of the so-called chemical castration and other ways of changing biochemical environment in convict’s brains with pharmaceutics. Additionally, it has been recently experimented even with more intense and direct interventions into perpetrators brains, such as deep brain stimulations and neurosurgeries.
Although some methods of changing criminals’ brains seem intuitively less and other more acceptable, it is extremely difficult to find a principled answer to the questions which interventions and in what circumstances can be ethically and legally justified. Generally valuable guiding principles in bioethics, such as respect for moral autonomy, free autonomous decision, informed consent, as well as the principles of non-harm and benefit lose much of their guiding power in the specific circumstances of the interface of the penal law and interventions into the brain. This doctoral thesis, therefore, once again turns to the principle of respect for human dignity and personality and calls for a thorough scrutiny of every individual case through the lens of this principle.