Biology, Brains, and the Supreme Court


It’s been a banner week for the Supreme Court of the United States.  Upholding the Affordable Care Act mandate, striking down key provisions of Arizona’s anti-immigration law, and striking down the provision that juveniles convicted as adults serve a mandatory prison term without chance of parole as a violation of the 8th Amendment ban on cruel and unusual punishment. As a scientist, I was immediately ECSTATIC to hear that the provision that juveniles convicted as adults serve mandatory life sentences was struck down. Regardless of how you feel about this law, I thought this is the perfect example of how biological science, social science, and lawmaking intersect in such a way as to do what they should do… inform public policy.  In this era where scientists can be purchased for a fee, we see so little cooperation between different disciplines in a way that actually affects real public policy in a way that upholds scientific truth, and I couldn’t be more excited about that.

Reforming the juvenile justice system to what are more humane levels, in the 1988 case Thompson v. Oklahoma, the Supreme Court struck down the practice of executing children under the age of 16 and extended that provision to the age of 18 in 2005 in the Roper v. Simmons decision.  In the 2010 Graham v. Florida decision, the Supreme Court struck down mandatory life sentences for juveniles tried as adults that did not commit murder, saving 129 juvenile prisoners from execution.  And until this past Monday, any juvenile tried and convicted as an adult had to serve a mandatory life sentence without the possibility of parole, the sentence for adults convicted of the same crime if they resided in a state where those sentencing guidelines exist. There are some 2500 juveniles in 28 states currently in prison serving this sentence, among the toughest in the world.  With Associate Justice Elena Kagan writing the majority opinion, the Supreme Court voted 5-4 to strike down this provision, allowing the court to consider mitigating, case-specific circumstances while determining the punishment phase of crimes in which adolescents are tried as adults in the case of murder.

Arguments for doing away with the mandatory life sentence without parole have included the understanding that teenagers often behave impulsively in risky situations and respond to situations emotionally, not rationally.  Most kids caught up in criminal activity act as a group where things often boil out of control, with little understanding of the consequences of their actions.  Many juvenile offenders are raised in violent homes and know no difference.  Additionally, young offenders are more susceptible to false confession which can increase the likelihood of wrongful convictions.

So, biologically how does age finally catch up with physical activity and impulsiveness?  Developmental biologists stress that the frontal lobe, particularly the prefrontal cortex, which contains the majority of dopamine sensitive neurons is the source of impulse control, social and sexual behavior, spontaneity, and the ability to predict the outcomes of actions (among other things), and the cable of nerves connecting both sides of the brain are not fully formed in many adolescents, leading to teenage impulsivity and mood swings.  Indeed patients with frontal lobe lobotomy or traumatic injury have shown deficits in problem solving ability, behavioral spontaneity, dramatic change in social behavior and failure to understand feedback from their surroundings, more specifically discussed here.  Psychologist Michael J. Bradley states that the critical part of the brain that has to do with making good judgments, moral and ethical decision making, and reining impulsive behavior doesn’t begin to develop until the age of 11 or 12 and is not fully developed until the age of 19 or 20.


As with all things splashed onto the national spotlight by our nation’s highest court, I didn’t know that this is actually a long debated topic, utilizing science as a way to overturn past overly punitive punishments for adolescents convicted of violent crime.  In fact, the biological relevance of juvenile conviction was brought into the spotlight during the 2005 Roper v. Simmons case during a time when sentences were getting stricter for youthful offenders. Adding law onto the social and biological framework adds another perspective, one from a Law Professor at Vanderbilt University, Terry Maroney, who thinks critically about the intersection of brain science, social science and the law.  She analyzes juvenile cases across different crimes and notes that there is actually little practical evidence that courts are considering the age and biological predisposition when making court rulings.  She also believes that brain science actually has little to do with the rulings because we already know that teenagers are more impulsive, less experienced, and less likely to think critically about their actions prior to doing them, however does believe that the prosecution, who state that brain science doesn’t matter in sentencing, are not correct either.  At the heart of her argument is that each case needs to be considered individually based on age, developmental stage, and reasoning capability. She talks her research in this very interesting Science Network video.

Amicus Briefs written by the Coalition for Juvenile Justice (CJJ) and The American Psychological Association (APA) in support of the defendant in the Roper v. Simmons case highlight functional MRI studies that show the differences between adolescent and adult brains by comparing subjects completing a series of different tasks, and a longitudinal study by Jay N. Giedd and coworkers following over 100 individuals scanned at least 5 times over 10 years between childhood and adulthood, outlines the developmental changes over the course of adolescence.  Of particular note is the dynamic change that the brain undergoes in composition between adolescence and adulthood; although the volume of the brain does not change, the ratio of white to grey matter does, with an overall decrease in grey matter and an increase in white matter.  This decrease in gray matter is thought to result from pruning within the brain, and strengthening the connections between the remaining neurons by increasing the amount of myelination, and therefore increasing the density of white matter.  This process continues in at least some cases up to the age of 22.  Find the APA amicus brief, and appropriate scientific citations for this case here and the CJJ amicus brief and containing appropriate scientific citations here.


My thoughts in this matter, and presumably the legislation that was passed by the Supreme Court in no way are intended to undermine the suffering of those who experienced loss at the hands of juvenile offenders, and I am fortunate that so far I have not been affected by this myself. It is important to note that this legislation strikes down the MANDATORY sentencing of juveniles to life in prison without parole in the case of murder.  The possibility of sentencing juveniles to life in prison is still a possibility.  Fundamentally cases like these are teaching developmental biologists, social scientists, and law professionals that the age of 18 is just an arbitrary number, and that development and neurological reasoning should be considered on a case by case basis.


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