Introduction
The traditional model of criminal justice is built upon the idea of a rational actor who makes a free choice to break the law and therefore deserves punishment. However, advances in psychology and neuroscience increasingly challenge this foundation, suggesting that for some individuals, criminal acts are not the product of free choice but are instead influenced or even dictated by underlying mental health conditions. This article will explore this tension. It will begin by briefly considering the psychological and neurological factors that may precede a criminal act before examining how the legal system in England and Wales grapples with this issue. This article will argue that while the law has developed specific mechanisms, such as the defences of insanity and diminished responsibility and therapeutic sentencing options, to divert some mentally disordered offenders from punishment, its approach remains cautious and fragmented, struggling to reconcile the principles of responsibility with the realities of mental illness.
The 'Criminal Brain': A Challenge to Legal Assumptions?
Criminological and psychological theories have long sought to understand the internal and external factors that lead to offending. Modern research has increasingly focused on the brain itself. For example, studies have suggested that dysfunction in the prefrontal cortex, an area of the brain responsible for executive functions like decision-making, impulse control, and understanding future consequences, can be linked to antisocial and criminal behaviour (Raine, 2008). Similarly, the amygdala, which processes emotions like fear and aggression, has been implicated. These biological predispositions do not operate in a vacuum; they interact with environmental factors, such as childhood trauma or substance abuse, to shape an individual's behaviour.
Furthermore, specific psychiatric diagnoses are statistically over-represented in the prison population. Conditions such as Antisocial Personality Disorder (ASPD), characterised by a disregard for the rights of others, and psychopathy, which involves a lack of empathy and remorse, present a significant challenge to the legal system. However, the law does not automatically excuse behaviour simply because it can be linked to a neurological or psychological abnormality. The cornerstone of criminal liability in England and Wales is the combination of actus reus (the guilty act) and mens rea (the guilty mind). The law presumes that adults are rational and autonomous, and therefore possess the required mens rea for an offence. As such, evidence of a "criminal brain" is not in itself a defence. Instead, the law has carved out specific, and narrow, legal doctrines to accommodate severe cases where mental disorder is seen to negate criminal responsibility.
Legal Defences: A Limited Recognition of Mental Disorder
The English legal system provides two main defences where a defendant's mental state at the time of the offence can be called into question: insanity and diminished responsibility.
The defence of insanity is a general defence, applicable to any crime. However, its legal definition is notoriously restrictive and medically outdated. The governing test is laid down in R v M’Naghten (1843), which requires the defence to prove that, at the time of the act, the accused was "labouring under such a defect of reason, from disease of the mind, as not to know the nature and quality of the act he was doing; or, if he did know it, that he did not know he was doing what was wrong." This test has been heavily criticised. The term "disease of the mind" is a legal, not a medical, concept and can encompass conditions like epilepsy or diabetes, while the focus on "knowing" (a purely cognitive test) fails to account for defendants who may know their actions are legally wrong but are unable to control their conduct due to their mental condition (Mackay, 2014). Consequently, the insanity defence is rarely used and is widely considered unfit for purpose, as highlighted by the Law Commission in its scoping paper on the issue (Law Commission, 2013).
A more modern and medically informed approach is found in the partial defence of diminished responsibility. This defence applies only to murder and, if successful, reduces the conviction to manslaughter. As amended by the Coroners and Justice Act 2009, section 2 of the Homicide Act 1957 states that a person is not to be convicted of murder if they were suffering from an "abnormality of mental functioning" which (a) arose from a recognised medical condition, (b) substantially impaired their ability to understand their conduct, form a rational judgment, or exercise self-control, and (c) provides an explanation for the killing. This updated definition moves away from the archaic language of M’Naghten and explicitly grounds the defence in medical evidence. The requirement of a "recognised medical condition" allows the law to evolve alongside psychiatric understanding. The focus on the effect of the condition on the defendant's abilities, particularly the ability to exercise self-control as seen in cases like R v Byrne (1960), offers a more nuanced assessment than the purely cognitive insanity test. However, the meaning of "substantially impaired" remains a matter for the jury, with the Supreme Court in R v Golds (2016) confirming it means an impairment which is "important or weighty," a threshold which can be difficult to consistently apply.
Beyond Conviction: Legal Management through Treatment
The question of how to deal with mentally disordered offenders extends beyond the trial process. Even where a defendant is found guilty, the courts have powers to direct them towards treatment rather than punishment. This represents the most direct answer to the proposition that offenders with mental health issues can be "legally managed" instead of punished. The primary statutory framework for this is the Mental Health Act 1983 (MHA 1983).
Under section 37 of the MHA 1983, a court can make a "hospital order" for an offender convicted of an imprisonable offence. This allows for the person to be detained in a hospital for treatment. To make such an order, the court must have evidence from two registered medical practitioners that the offender is suffering from a mental disorder of a nature or degree that makes hospital treatment appropriate. The court must also be satisfied that, considering all the circumstances, including the nature of the offence and the offender's character, a hospital order is the most suitable method of disposal.
For more serious offences, or where the offender is considered to pose a risk of harm to the public, the Crown Court can attach a "restriction order" under section 41 of the MHA 1983. This order, which is made for the protection of the public from serious harm, places the offender under the authority of the Ministry of Justice. They cannot be discharged, transferred, or given leave without the consent of the Secretary of State for Justice. This system creates a clear therapeutic alternative to a prison sentence, acknowledging that for some, treatment in a secure medical environment is more appropriate for both the individual and for public protection than incarceration (Bartlett and Sandland, 2014). These orders directly address the problem of the offender’s mental state by prioritising treatment, but they are not a 'soft option', as they can result in detention for an indeterminate period until the offender is deemed safe for release.
Conclusion
The criminal law of England and Wales, while rooted in principles of culpability and punishment, does not entirely ignore the complex relationship between mental health and offending. It has created pathways that divert individuals away from the purely punitive sanctions of the justice system and towards a therapeutic model of management and treatment. The defence of diminished responsibility reflects a modern, medicalised understanding of impaired mental functioning, even if the older insanity defence remains a relic. More significantly, the sentencing powers under the Mental Health Act 1983 provide a concrete mechanism for "legally managing" offenders whose crimes are linked to their mental disorder, prioritising treatment over punishment.
However, this therapeutic approach operates as an exception rather than the rule. The legal tests for defences are stringent, and the availability of hospital-based disposals depends on the specific diagnosis and the availability of resources. The system remains a compromise, attempting to balance the public's demand for punishment and safety with a growing recognition that some offenders are in need of help, not just retribution. The journey from a punitive to a fully therapeutic model of justice is far from complete, but the existing legal framework shows a clear, albeit limited, acknowledgment that what goes on in an offender's mind is of profound importance.
References
Bartlett, P. and Sandland, R. (2014) Mental Health Law: Policy and Practice. 4th edn. Oxford University Press.
Coroners and Justice Act 2009, c. 25.
Homicide Act 1957, c. 11.
Law Commission (2013) Criminal Liability: Insanity and Automatism – A Scoping Paper. Available at: [https://s3-eu-west-2.amazonaws.com/lawcom-prod-storage-11jsxou24uy7q/uploads/2015/03/lc342_insanity_and_automatism_scoping_paper.pdf](https://s3-eu-west-2.amazonaws.com/lawcom-prod-storage-11jsxou24uy7q/uploads/2015/03/lc342_insanity_and_automatism_scoping_paper.pdf).
Mackay, R. D. (2014) ‘On being a mad ‘expert’ in the criminal courts’, The Journal of the Royal College of Physicians of Edinburgh, 44(4), pp. 336-340.
Mental Health Act 1983, c. 20.
Raine, A. (2008) ‘From genes to brain to antisocial behavior’, Current Directions in Psychological Science, 17(5), pp. 323-328.
R v Byrne [1960] 2 QB 396.
R v Golds [2016] UKSC 61.
R v M'Naghten (1843) 10 Cl & F 200.
