Exploring a Misuse of Neuroscience: How Biology Has Been Used to Remove Responsibility in Youth

The foundation of science requires self-policing about its excesses. It is understandable for scientific arguments to be tested and for their boundaries to be examined. In this article, we would like to focus specifically on the use of neuroscience by mental health experts to argue for diminished or lack of responsibility in youthful criminal offenders. Over the past years, courts throughout the country have been raising the age of responsibility when assessing responsibility and sentencing based on selective understanding of neuroscience.^1,2

To understand the scope of the problem, one should understand that many states use different sentencing guidelines for youthful offenders. For example, in California, if a youthful offender is convicted of murder and is not tried as an adult, the maximum term for detention is about 23 to 25 years of age.³ Being released at 25 for murder renders the question of, ‘what age constitutes a youthful offender?’ particularly important. In our experience, mental health experts and some publications attempt to argue that individuals up to the age of 30 should receive sentences in the range of minors rather than adult guidelines.⁴

Hence, journalists and courts have asked, “does childhood end at 18?”⁵ or more formally, is neurodevelopmental development mature enough at age 18 to justify adult sentencing? A commonly cited case is State v O’dell. Ten days after his 18th birthday, Sean O’dell raped a 12-year-old girl. In their 2015 decision, the supreme court of Washington stated that “neurological studies” show that “‘parts of the brain involved in behavior control’ continue to develop well into a person's 20s.”⁶ The court highlighted that the “dorsal lateral pre-frontal cortex, important for controlling impulses, is among the latest brain regions to mature without reaching adult dimensions until the early 20s”⁷ referencing a highly-cited 2004 study by Giedd of 145 adolescents.⁸

We do not claim that those arguments are without merit or should not be introduced in court, but instead we argue that they are overstated, insufficient, and often irrelevant.

Counterpoints

1. The neuroscience in these cases is usually not about the defendant.

In our experience, frequently, young individuals are being declared less responsible simply because of their youth by an expert who had no specific neuroscientific evidence of their particularly youthful brain. It has become commonplace for experts to overly rely on generalized population level data without contextualizing it to the individual case. Courts allow testimony that an individual’s frontal lobe is underdeveloped, that their amygdala is overactive, and that their executive function is so poor as to prevent the inhibition of impulses on the sole basis of imaging studies done on other individuals. We acknowledge some individuals have impaired and delayed development; those should be measured using appropriate tools with adequate validation markers to render them useful in the forensic setting.

2. Average curves hide the person in front of the court.

People in their late teens and early 20s have a higher average rate of impulsive or peer-influenced mistakes than older adults. That is a statement about a group. Courts ask a different question: the degree of responsibility to be held against an individual person. A higher base rate of poor decisions in an age group is not evidence that a specific offense was involuntary. Yet, on the other hand, one could also point out that most individuals in the same age band, with the same brain challenges the expert is describing, do not commit those crimes.

Group studies of brain maturation and executive function report mean differences by age. In 2010, Dosenbach et al used imaging in individuals aged 7 to 30 to compute a functional-connectivity maturity index.⁹ Chronological age accounted for only about half the variance; people of the same age already differed widely from one another. An average curve does not tell the court whether this 20-year-old has the immature control the expert is describing.

3. Larger cognitive data do not support “not an adult until 25.”

In 2023, Tervo-Clemmens et al published a much larger study of executive function than prior reviews.¹⁰ Examining more than 10,000 individuals from age 8 to 35 in 4 large and independent data sets, and over 23 executive function measures, they formulated a more thorough review of the trajectory of executive function. Executive function rose rapidly from 10 to 15, improved more slowly through mid-adolescence, and stabilized at adult levels in late adolescence, about 18 to 20. More than 95% of the age-related change in accuracy, and nearly all the change in speed, occurred before 18.

They point out that prior studies were much smaller, using less than 200 individuals, like the Giedd study, or much narrower in focus, examining very narrow measures. Executive function is not the same thing as decision-making under peer pressure, intoxication, or high arousal. That limits the claim that young adults cannot plan or inhibit a response the way adults can. This large-sample cognitive evidence indicates that capacity is largely in place by 18, not 25 or 28.

4. If brain change means diminished responsibility, the category has no upper bound.

The brain does not freeze at 25. Gray-matter, white-matter, and the size of many brain regions keep changing through midlife and into old age. In 2017, Farokhian et al compared younger adults with older adults, and found widespread reductions in frontal, insular, and cingulate gray matter and extensive white-matter decline.¹¹ Those changes represent ordinary aging, not a rare disease of brain dysfunction. If the mere fact of ongoing neural change were proof of reduced culpability, this logic could apply to all age groups.

To the contrary, when the defendant is old, we do not treat age or an aging brain as the finding. The evaluation includes cognitive screening, neuropsychological testing, functional history, and a specific inquiry into what this defendant could understand and control at the time of the offense. The inconsistency highlights this point. Brain changes in the 20s are offered as evidence of diminished blame. Yet, in older adults we still require evidence of impaired incapacity.

5. A lot of the supporting rhetoric is circular.

“Anyone with common sense who knows someone between 18 and 22 cannot reasonably argue that they are able to make the same judgments an adult would make.”⁵ Arguments that we are not allowed to drink until age 21, rent a car until 25, or get married later than prior generations, or keep our parents insurance longer do not in themselves provide any scientific information to educate the court on how to make decisions about responsibility.^5,6,12 They tell the court what legislatures decided in other domains. They do not tell the court what this defendant could understand or control.

Furthermore, the same method can produce the opposite conclusion. At 18, a person may vote, serve on juries, sign a contract, be drafted, and enlist in the military. There are also biological examples, like puberty arriving earlier, not later. Additionally, legislatures have already treated some minors as capable of medical decisions. In California, a minor 12 or older may consent to some medical care, in Delaware as well. We are not arguing that the age of adulthood should fall. We are pointing out that policy ages can be lined up on either side of 18. Neither tells the court what this defendant could understand or control.

6. We already make complex decisions without imaging.

Inpatient psychiatrists regularly consider this. Imagine a 16-year-old patient punching another one. A psychiatrist would of course consider their state of mind, their intellectual capacity, their reality testing, and their moral development prior to assessing the appropriate response and intervention. A blanket claim that ‘the prefrontal cortex is still developing’ means they cannot be held responsible is short-sighted. Similarly, when a young child acts inappropriately, parents make similar considerations when rendering judgment. It should be our expectation that psychiatric experts and judges be held to the same considerations rather than rely on abstruse neuroscientific jargon.

7. Moral understanding is established science and arrives much earlier.

Our attraction to imaging has produced an amnesia for older, well-established, developmental science. The question that matters is who is responsible and how much—not whether a group-average image can be projected onto the defendant. Psychiatrists have long been taught, from Piaget and Kohlberg, that children grasp rules and the wrongfulness of serious harm well before adolescence.¹³ That literature has limits. Knowing a rule is not the same as holding to it. Our duty demands of us that if we routinely are going to equivocate adults to children and effectively hold them blameless for the commission of a crime, we must then explain what in that person failed to develop specifically when other children can see the act as being wrong and control themselves.

Concluding Thoughts

While the developing understanding of neuroscience offers insights into brain maturation, using these findings to diminish youthful offenders of responsibility poses ethical and scientific challenges. The appropriation of neuroscience in the courtroom, without rigorous examination of its relevance, impedes the integrity of the court process. The counterpoints listed here undercut the claim that maturity arrives at 25. The larger study of executive function undercuts that maturity happens at 18.¹⁰ The fact that brains keep changing undercuts the claim that change itself is an excuse.¹¹ The developmental literature undercuts the claim that young adults do not understand right from wrong.¹³

What remains is a rededication to expertise in the core domains of forensic work: individual capacity, knowledge, illness circumstance. That is forensic psychiatry. It is also justice. Ultimately, the reliance on inaccurate and imprecise neuroscience as a blanket rationale for diminished responsibility in youthful offenders underscores a troubling trend in legal and psychiatric practices. The pendulum of forensic evaluation will continue to swing, as it always has, pushed by the shifting pressures of promising new scientific developments. Our duty requires integrating those developments without surrendering the grounded, contextual judgments that justice demands.

Dr Badre is a clinical and forensic psychiatrist in San Diego, California. He teaches medical education, psychopharmacology, ethics in psychiatry, and correctional care. Dr Badre can be reached at his website, BadreMD.com. His general textbook of psychiatry is available on Amazon.

Dr Shronts is a fourth-year psychiatry chief resident at Naval Medical Center San Diego. He is a veteran with over 20 years of military service. He is interested in forensics and psychodynamic therapy.

References

1. Steinberg L. The influence of neuroscience on US Supreme Court decisions about adolescents' criminal culpability. Nat Rev Neurosci. 2013;14(7):513-518.

2. Maroney TA. The false promise of adolescent brain science in juvenile justice. Notre Dame Law Review. 2013;85(1).

3. California Welfare and Institutions Code § 1769(b)

4. Somerville LH. Searching for signatures of brain maturity: what are we searching for? Neuron. 2016;92(6):1164-1167.

5. Pishko J. Does childhood end at 18? The Appeal. August 17, 2017. Accessed September 24, 2026. https://theappeal.org/does-childhood-end-at-18-7dab03c5e829/

6. State v. O'Dell, 183 Wash.2d 680

7. Giedd JN. Structural magnetic resonance imaging of the adolescent brain. Ann N Y Acad Sci. 2004;1021:77-85.

8. Giedd JN, Blumenthal J, Jeffries NO, et al. Brain development during childhood and adolescence: a longitudinal MRI study. Nat Neurosci. 1999;2(10):861-863.

9. Dosenbach NU, Nardos B, Cohen AL, et al. Prediction of individual brain maturity using fMRI. Science. 2010;329(5997):1358-1361.

10. Tervo-Clemmens B, Calabro FJ, Parr AC, et al. A canonical trajectory of executive function maturation from adolescence to adulthood. Nat Commun. 2023;14(1):6922.

11. Farokhian F, et al. Age-related gray and white matter changes in normal adult brains. Aging Dis. 2017;8(6):899-909.

12. Sawyer SM, Azzopardi PS, Wickremarathne D, Patton GC. The age of adolescence. Lancet Child Adolesc Health. 2018;2(3):223-228.

13. Tasman A, Riba MB, Alarcón RD, et al, eds. Tasman’s Psychiatry. 5th ed. Springer Cham; 2024.