Abstract

This White Paper reports the latest developmental and brain science to inform judges, attorneys, and policy makers about critical research developments.9 This White Paper is intended to facilitate science-informed decision-making and application of updated research findings in law and public policy bearing upon adolescence and criminal proceedings. In the landmark case Miller v. Alabama (2012), the United States Supreme Court eliminated mandatory life-without-parole sentences for murders committed by youth under age 18.10 This decision was informed by an evolving understanding of adolescent brain development and behavioral research. Since then, scientific research has emerged which reinforces the reasoning of the Miller decision and, if its implications are accepted, extends much of the science that resonated with the Miller court to late adolescents (ages 18–21). Maturation of brain structure, brain function, and brain connectivity continues throughout the early twenties.11 This ongoing brain development has profound implications for decision-making, self-control and emotional processing. For example, new neuroscience research reveals that during emotionally charged situations, late adolescents (ages 18–21) respond more like younger adolescents (ages 13–17) than like young adults (ages 22–25) due to differences in brain maturation.12 Compared to young adults above age 21, late adolescents (ages 18–21) also take more risks and engage in more sensation-seeking behavior.13 Due to differences in brain development, late adolescents are more likely than young adults to respond to immediate outcomes and are less likely to delay gratification.14 The presence of peers can intensify these behaviors, and the brains of late adolescents are more responsive to peer involvement than those of young adults.15 Late adolescents are also more easily swayed by adult influence and coercion than their adult counterparts.16 These developmental differences in behavior have direct implications for legal decision-making, including waiving Miranda rights, susceptibility to false confessions, and making ill-advised trial decisions (e.g., plea decisions). 

Adversity, racism, and poverty also have a profound impact on health, quality of life, and criminal justice involvement.17 As discussed below, adolescents who have experienced adversity, racism, and poverty are significantly overrepresented in juvenile and criminal justice systems. However, while these experiences pose developmental challenges, they do not dictate fate, as late adolescents are also remarkably resilient, and their developing brains are poised for positive learning through interventions and rehabilitation.18 For late adolescents engaged in criminal behavior, research consistently indicates that most will not continue to offend and become adult repeat offenders through their twenties, thirties, and beyond.19 This has significant implications for both policy and the legal system. For example, this high rate of desistance from even serious or persistent adolescent offending as youth move into their early to mid-twenties renders it impossible to reliably predict, based on current science, which individual youth will continue to offend into adulthood and which will desist as they mature. There is certainly no basis in science to reliably determine that an individual youth at the time of sentencing in adolescence is incapable of rehabilitation (or even unlikely to achieve it) over the course of a lifetime.