Adulthood is a social construct. For that matter, so is childhood. But like all social constructs, they have real consequences. They determine who is legally responsible for their actions and who is not, what roles people are allowed to assume in society, how people view each other, and how they view themselves. But even in the realms where it should be easiest to define the difference—law, physical development—adulthood defies simplicity.
When does a juvenile legally become an adult? This is literally a life- or-death question because the United States Supreme Court held that the Constitution prohibits the imposition of capital punishment on a juvenile.
Despite the enormous consequences, the Supreme Court has spent little time defining what it means to be a juvenile. Instead, the Court has simply accepted the relatively recently adopted conventional wisdom that a person is considered an adult on his or her eighteenth birthday.
But there is no rational or scientific basis for drawing the line between being an adult and being a juvenile at age eighteen. Indeed, recent scientific research—the same brain research the United States Supreme Court has used to adopt legal principles that both protect and harm adolescents—proves that brain maturation actually occurs from ages ten to twenty- seven.
This article will explore whether the line between a juvenile and an adult should remain at eighteen. It begins by exploring the history of distinguishing childhood from adulthood. Next, this article details the legal system’s differing treatment of certain ages. Then, it details the criminal justice system’s treatment of persons below the age of eighteen. Next, this article discusses the science behind cognitive development. Then, it discusses Supreme Court decisions that affect rights of individuals based on age. Finally, the article concludes that drawing the line of adulthood at age eighteen without consideration of an individual’s characteristics is arbitrary under the Constitution.