My Brain Made Me Do It!
Your brain is on trial
“It’s just another argument with a difficult customer,” Rebecca thought to herself. In early March 2013, the Vacation Host Inn employee was trying to explain to Penny Coleman, a resident, that her children could not ride their bikes around the perimeter of the motel. Later that day, Penny’s husband, Kelvin Lee Coleman, took up the issue with the front office staff. Concerned about how heated the confrontation was becoming, an office clerk called the county police, who decided that that was no evidence of direct threat and left.
Five hours later, Kelvin returned to the motel, armed, and fired shots at Lester Carter and Glendora Johnson, a maintenance man and a maid at the inn, respectively. Both Carter and Johnson died from their injuries. Kelvin was later arrested and claimed he was innocent.
In The State of Florida v. Kelvin Lee Coleman Jr., Coleman was accused of first-degree murder, which made him a candidate for capital punishment. Expert witnesses came to the stand to defend Coleman, explaining to the jury that Coleman had a diminished capacity to conform to legal norms and appreciate the wrongness and criminality of his actions. His neglectful upbringing and poor home life had changed his worldview, an expert testified. His attorneys presented various neuroimaging, neurophysiological exams and evaluations as evidence that the defendant showed signs of traumatic brain injury, foetal alcohol spectrum disorder and even chronic traumatic encephalopathy — all a result of his childhood trauma.
The jury was convinced. To them, the neuroimages proved that his brain was abnormal as a result of his childhood; thus, he could not necessarily be held responsible for his actions. They agreed that he lacked impulse control because of these abnormalities. And, they agreed that Coleman had a below-average intelligence level. These were seen as mitigating circumstances, which, according to the jury, outweighed the aggravating factors. Coleman evaded the death sentence and was instead sentenced to life imprisonment without parole. Neuroscience saved his life.
Applying scientific concepts and data to the law is not a new phenomenon. Biology underpins forensics, aiding legal investigations. Psychology has shown us how unreliable eyewitness testimonies can be. Empirical economic principles are the foundation for tort and antitrust laws.
Over the past couple of decades, neuroscience has become increasingly important in the legal world, especially criminal law. The claims that Coleman’s defence team raised — that his brain abnormalities caused by his traumatic formative years were enough to avoid the death penalty — are no longer unusual in the American criminal justice system and are among the many ways the brain finds itself on trial. In the US, between 2005 and 2015, there were almost 3000 judicial opinions that mentioned the use of neuroscience as part of the criminal defence. In 2012 alone, there were over 200 opinions — double that of 2007 — in which defendants argued, essentially, that their ‘brains made them do it’.
As with any emerging field, there are grumblings within the scientific community regarding the use of neuroscience in the courtroom. A small minority even call for its outright ban, noting that the current state of neuroscience cannot establish a causal relationship between behaviours and brain abnormalities since our understanding is far from complete.
The interface between criminal law and neuroscience — neurolaw — has immense potential. Neuroscience is already entrenched in the American legal system, influencing the outcomes of more and more criminal cases. Rather than unproductively calling for an outright ban, neuroscientists should play a part in educating legal stakeholders and the public about the prudent development of the use of neuroscience in the criminal justice system. When used responsibly, neuroscience can provide the tools to improve the accuracy and decrease errors in criminal cases.
The State of Florida v. Kelvin Lee Coleman Jr. is just one of many examples of how neuroscientific evidence is used to demonstrate diminished criminal responsibility in order to receive a lighter punishment. Understanding the brain is useful for criminal law as mental states are central for establishing responsibility. Responsibility is a complex concept, and it is almost always a contentious issue in the courtroom. Our understanding of responsibility is inherently tied to the societal normative assumptions we have about how humans make decisions. We assume that a person chose to undertake the action or inaction that led to the consequence that the law is now holding them responsible for. For one to be morally responsible for the outcome of an act, we usually require one to intentionally act to cause it. We also assume that people understand that their actions can have important outcomes and consequences for others — the likely outcomes of their actions must drive their choices. In order for all of this to happen, we assume the person has the neurocognitive capacity to voluntarily choose their action or inaction and understand the consequences of it at the time of committing the crime.
This is mens rea (“guilty mind” in Latin), a core tenet in Anglo-American criminal jurisprudence that needs to be fulfilled to establish criminal responsibility. It asks if the defendant is capable of the kind of mental state necessary for moral responsibility. An individual cannot be criminally liable for an offense unless the prosecution establishes that the defendant committed an unlawful voluntary act or omission — actus reus (“guilty act”) — and committed the act with intent or requisite mental state — mens rea. The criminal defence team needs to demonstrate one of four mental states to establish mens rea: purposeful, knowing, reckless, or negligent.
Neuroimaging can help us determine the presence or absence of mens rea. To be a morally responsible agent, one must have the relevant mental capacities. Mental capacities are embedded in brain mechanisms (the ‘hardware’); so, to be a morally responsible agent, one needs the relevant brain mechanisms. Neuroimaging can individually assess and identify if the person possesses these mechanisms. Based on various cognitive neuroscience studies, there are some localised brain regions theorised to be the roots of impulse control, moral decision-making, intentionality, and planning. Abnormalities of the prefrontal cortex and related subcortical structures, such as the parietal cortex, for example, have been correlated with violent behaviour, impulsive aggression, moral reasoning, and agency. Therefore, in theory, using neuroimaging to empirically demonstrate deficits in such brain regions might give rise to claims that the defendant lacked the ability to formulate intentions or act knowingly, indirectly showing that they lacked mens rea for a criminal offense.
Neuroimaging evidence has also been used to establish legal insanity. By pleading not guilty by reason of insanity, a defendant admits to committing the actions but claims a lack of culpability due to a mental illness. The insanity defence derives from the idea that certain mental illnesses can interfere with the individual’s ability to form, and thus achieve, the mens rea requirement. This is different from diminished capacity, which Coleman claimed, as it allows defendants to plead guilty to a lesser crime, while reason of insanity allows defendants to plead not guilty. Courts are increasingly relying on neuroimaging data as evidence for weighing the insanity defence.
In American criminal jurisprudence, the mens rea requirement aims to ensure proportionality. Punishment is proportional to the offender’s blameworthiness; only those who meet the criteria for one or more of the four mental states under mens rea — therefore morally responsible for the act — will be punished.
But is this evidence sufficient to demonstrate criminal liability? Using neuroscience to mitigate or nullify criminal liability by presenting evidence of abnormality seems very relevant. In fact, however, it is only weakly so. Neuroimaging evidence does not make causative links between the neurobiological impediment and the criminal offence. Just because the defendant’s brain structure is atypical does not mean that it is a major contributing factor to the criminal behaviour they engaged in. No brain abnormality, or even for that matter, genetic variation, has been proven to have a deterministic effect on behaviour.
“What they’re doing is making what I call the fundamental psycho-legal error. This is the belief that once you have found a partially causal explanation for a behaviour, then the behaviour must be excused altogether. All behaviour has causes, including causes at the biological, psychological, and sociological level. But causation is not an excusing condition.”
That is not to say that there is no evidence linking brain and behaviour. Abnormal brains tend to lead to abnormal behaviours. However, there is no causative effect, nor is there a strict correlation that can allow us to predict behaviour based on, for instance, percentage of grey matter loss. This limited understanding is due to the limitations of neuroscience: we are not able to directly manipulate the living human brain and we extrapolate results from model organisms to human behaviour at our peril.
Meanwhile, there is ongoing controversy surrounding the reliability of neuroimages, which the criminal justice system is becoming increasingly dependent upon. This ties back to mens rea. Defence attorneys using neuroscience in the courtroom would have us believe that our actions are bound by a series of determined physical events that necessarily lead to a certain behaviour. This casts doubts on the entire mens rea concept. Neuroimaging evidence showing that a behaviour is caused by a physical and tangible factor (e.g., a lesion in the parietal cortex) leaves no room for mental processes or the self. Society’s intuition is that of the dualist, i.e., that the mind and brain are separate.
Although the law does not rely on mind-brain dualism, our intuitive sense of justice and thus, our willingness to affirm the law does indeed rely on it. Neuroscience evidence meant to excuse criminal behaviour would undermine our common sense and conception of free will. According to Greene and Cohen, who published a controversial article on the paradigm clash, neuroscience-driven criminal law would have to be largely consequentialist. We would still dish out punishments such as prison time because it reduces adverse consequences, like the risk of recidivism, and it increases positive consequences, like public safety. However, we would not be able to punish people because they deserved it.
Morse counters this view. He posits that the intersection of neuroscience and law is nothing to be concerned about, for now. As long as neuroscience shows that human actions are partially caused by deterministic neural events, then the assumptions we hold of personhood and criminal responsibility are not being undermined.
Using neuroscience to temper punishment for adolescent offenders is typically met with more receptiveness. Adolescence is the period of transition from childhood to adulthood, often characterised by struggle and angst. It is the in-between developmental stage where teenagers seek independence from their guardians while remaining dependent on them. This is reflected in their brains, where cortical and functional circuitry development are highly dynamic. Regions that are phylogenetically older develop first, whereas more modern regions, which are associated with higher order functions, mature later. In particular, the prefrontal cortex — responsible for regulating behaviour and judgement — does not mature until the late teen years or even the early twenties.
This has led to the proposal of an imbalance model of brain development. The differential development of brain regions can lead to an imbalance in adolescents, causing them to rely more on the phylogenetically older regions, which are primarily responsible for emotions. Improvements in neuroimaging techniques have allowed neuroscientists to access new knowledge and define the brain regions implicated in the imbalance model. Magnetic resonance imaging (MRI) scans have shown that the frontal cortex — home to executive order functions — is the last region of the brain to fully develop. This increases teenage reliance on the amygdala, a phylogenetically older part of the brain that is characterised as emotional, impulsive and aggressive. This means that in relatively low-emotional stakes situations, the frontal cortex circuitry can trigger relevant and appropriate action and behaviour. In emotionally charged situations, however, the emotion-focused circuitry that is more mature overpowers rationality, meaning a teenager is less capable of exercising self-control. Thus, the neurobiological immaturity of an adolescent can make them more vulnerable to make poor decisions in fraught contexts. As they mature into adulthood, their capacity for self-control catches up.
This has led to criminal defence lawyers arguing for lighter sentences for juveniles compared to adults by relying on the ‘developing brain’ notion. It is based on the aforementioned proportionality principle that the American criminal justice system embodies. Through the lens of this principle, we would conclude that applying the same level of punishment that an adult receives — for the same crime — to an adolescent is excessive and disproportionate.
Developmental neuroscience has served as the scientific basis for recent constitutional prohibitions against the execution of juveniles. References to neuroscience in US Supreme Court opinions regarding adolescent culpability are becoming more frequent. A key example is Roper v. Simmons, where the defendant’s legal team contended that 17-year-old Christopher Simmons’s biological limitations meant that he could not fully control his actions. If so, then this would have made the death penalty a cruel and unusual punishment, in violation of the Eighth Amendment. Simmons’s legal team used neuroimaging to indicate that, when shown next a mature adult brain, the teenage brain had evidently not yet matured to that same level; knowing this, how could we sentence Simmons in the same way as a normal healthy adult? This led to the landmark decision in which the US Supreme Court held that it was unconstitutional to impose capital punishment for crimes committed under the age of 18.
Creating a link between the explanatory power of neuroscience and the normative power of the law is challenging due to the clashing of these paradigms. This has not stopped judges from dedicating more space in their opinions to discussing neuroscientific evidence in detail, including citation of scientific literature and expert testimonies.
Yet, we must be careful not to be seduced by the allure of neuroscience, even as it is being used more often to reduce sentences. Presenting neuroimaging is compelling, as it provides seemingly strong explanatory power, implying that the brain — and the injured brain, in particular — is the ultimate cause of one’s actions and mental processes.
What does it mean if we are all just a victim of nature?
But being too reductively neuro-centric will impede the search for the true causes of actions during a criminal trial. Yes, brain function influences human behaviour. And yes, the law seeks to regulate human behaviour in ways that are socially useful. Thus, it follows that neuroscience should interact with the law to ensure that the criminal justice system is truly fair and in line with the way humans function. But, on the way to the neurolaw revolution, both law and neuroscience need to proceed carefully in order to understand each other’s nuances and limitations.
