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May 17, 2023

The Pros and Cons of Neuroscience in the Legal System

Aiden Fel

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The role of neuroscience in criminal liability has been a topic of much debate in recent years. Some argue that neuroscience is irrelevant in criminal court, while others contend that it can help establish that many criminals lack control over their behavior. However, the truth is likely somewhere in the middle, as certain types of neuroscience evidence may prove useful and relevant in criminal trials.

There are five types of neuroscience evidence that can be applicable to criminal law:

The first type of admissible evidence includes data showing brain abnormality obtained through scans, which may diagnose the defendant with conditions such as frontal lobe disorder or traumatic brain injury (TBI). At present, this evidence is only weakly relevant to criminal liability because it fails to establish a causal link between the neurological impairment and the crime. In rare cases though, behavioral evidence may be sufficient to establish a connection between neurology and behavior, such as in cases where a brain tumor is shown to be a cause of impulsive behavior. Overall, evidence of the abnormality alone is usually insufficient to prove impairment or causation in criminal trials.

Second, research demonstrating a higher occurrence of criminal behavior among similarly impaired individuals can help to supplement evidence of a defendant's brain abnormality. One research study found that 73% of prisoners convicted of violent crimes had frontal lobe damage (FLD), while only 28% of those who committed non-violent crimes had FLD. However, this research only shows that a high proportion of violent individuals possess this brain abnormality and ultimately does not answer the central question of whether individuals with the abnormality are more likely to be violent. Courts have deemed this type of research as irrelevant and exculpatory because it does not explain how the abnormality contributed to the crime. Therefore, it tends to be no more useful than evidence of the abnormality alone.

Third, genetic and environmental factors that strongly predispose people to commit serious crimes may also be considered by criminal courts. However, even if the defense presents strong evidence that a crime is caused by neurological abnormality, evidence of planning or other factors can still undercut an insanity defense. In general, numerous difficulties in generalizing from a study to the case at hand continue to undermine the usefulness of effect-of-cause studies.

Fourth, neuropsychological testing provides insight into a particular defendant's functioning, including their capacity to self-control, ability to plan and form intent, and possess an awareness of risks. However, the testing provides limited insight into a particular defendant's functioning rather than providing the type of functioning that might accompany a particular brain abnormality. There are several obstacles to this approach such as malingering, difficulty of obtaining baseline data for relevant demographic groups, and the fact that testing results do not necessarily reflect the defendant's state of mind at the time of the crime. Moreover, science itself cannot provide a definitive answer to a normative question of how much "dysfunction" is required for legal purposes.

Lastly, individualized neuroscience findings can be used to compare the brain structure and functioning of defendants with juveniles or individuals with intellectual disabilities, which can be relevant at sentencing. The Supreme Court has exempted individuals with intellectual disability and juveniles from the death penalty, stating that they are categorically less culpable than the average criminal. Neuroscientific data can potentially be used to compare the brain structure and functioning of defendants with those of juveniles or individuals with intellectual disabilities, and this evidence can be considered relevant at sentencing. This approach is known as "scientific stare decisis." However, identifying those neurological characteristics that should be used for comparison continues to pose a scientific and legal challenge.

Thus, the usefulness of neuroscience in criminal trials or sentencing is limited under current law, and it is only likely to be considered in cases of significant cognitive or volitional impairment. Even in capital sentencing, the usefulness of neuroscience may be uncertain, although defense attorneys may still use such data as evidence.

Neuroscience may also offer useful tools for determining cognitive capacity. As the American population ages, the number of individuals suffering from Alzheimer's disease (AD) and other forms of dementia is expected to increase significantly. This raises important and wide-spread questions regarding legal competency and decision-making authority, particularly in the context of guardianship proceedings. These proceedings are often used to remove decision-making authority from individuals deemed legally incompetent and rely heavily on clinical opinions from experts when determining an individual's competency. However, the loss of autonomy when an individual is assigned a guardian can be all-encompassing, making it a mechanism of last resort for patients who lack capacity for medical decision making. Pursuing guardianship alternatives can be cumbersome and may require mobilization of support, navigating familial conflicts, or incorporating protections that lack the full force of the law, leaving individuals vulnerable to exploitation.

Many advocates have called for guardianship reform, noting that physicians can serve as important allies and advocates for patients with cognitive impairment at risk of incapacity to preserve their autonomy as long as possible. However, there is evidence that the current use of capacity evaluations by physicians may leave much to be desired.

For example, a 2007 study conducted by Moye and colleagues examined the quality of clinical evaluations for guardianship across three states with varying levels of statutory reform: Massachusetts, Pennsylvania, and Colorado. The study found that information provided by physicians on specific functional deficits was frequently missing, conclusory statements were common, and information about the individual's key values and preferences was almost never provided. Individuals were also rarely present at the hearing. It is clear that a continuing dialogue between clinical and legal professionals is needed to advance reform in guardianship and provide for the needs and protect the rights of adults who face guardianship proceedings. It is particularly noted that incapacity and the associated use of guardianship proceedings is a rising concern for older adults with neurocognitive or neuropsychiatric illness.

Advances in neuroscience and the discovery of biomarkers of AD may offer a more precise and sensitive method of assessing disease diagnosis and prognosis, which could greatly increase the accuracy of capacity evaluations and have profound implications for medicine, public policy, and law. The use of biomarkers could offer objective and empirical data to assist in competency assessments, but it also poses risks and raises important questions about how to balance performance-based assessments with the use of neurobiological metrics. Furthermore, given that changes to the brain occurs on a continuum rather than as a function of distinct stages, it is unclear how much weight should be given to biomarker evidence and how to protect against bias and over-diagnosis.

Although promising, current AD biomarkers are not yet ready for widespread use in medical practice or most legal settings. Even if validated, they are likely to be used, at least initially, alongside other diagnostic measures rather than in isolation. Furthermore, AD pathology can be present in individuals who do not exhibit cognitive symptoms, possibly due to cognitive reserve related to educational or occupational attainment. Despite these challenges, the discovery and clinical use of AD biomarkers are on the horizon, raising hope for their application in guardianship proceedings.

    Aiden Fel

    Ossining High School

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