As the legal system began treating juvenile offenders more like adults during the 1990s, scientists discovered significant neurological differences between the two groups.
Research has produced new insights into the development of the adolescent brain and was partly responsible for the U.S. Supreme Court’s decision last year to prohibit the death penalty for offenders younger than 18.
Although scientists once believed the brain was fully developed by about age 12, magnetic resonance imaging studies at the National Institute of Mental Health and elsewhere have shown in recent years that the adolescent brain continues to change.
One surge of neural growth occurs in the womb, but research in the late 1990s revealed a second massive change roughly between ages 6 and 12. Then gradually, the brain prunes its neural connections to work more efficiently.
The last part to fully develop, the prefrontal cortex, controls “executive functions” that affect things like suppressing impulses and understanding consequences. That stage isn’t completed until the late teens to early 20s.
The research aligns well with parents’ long-held conventional wisdom – that some teens behave erratically, make poor choices and have difficulty grasping consequences of their actions.
But a pre-eminent brain researcher says he was shocked when the nation’s highest court mentioned the studies in its opinion on the death penalty.
“My first instinct was that this research is not ready for prime time,” says Jay Giedd, chief of brain imaging at the NIMH. “But another part of me says that it should be at the table. It’s too far along to ignore but not far along enough to be used in individual cases.
“It’s rare when science spills over into social things,” he says. “Frankly, it scared me.”
Jennifer Woolard, an assistant psychology professor at Georgetown University, looks at teens’ behavioral choices from a different angle.
One study in which she participated, by the Philadelphia-based MacArthur Foundation Research Network on Adolescent Development and Juvenile Justice, found that about one-third of juveniles ages 11 to 13 and one-fifth of those 14 to 15 have “essential deficits” in their knowledge of the judicial process. The subjects – half of them incarcerated and half from the general population – often can’t distinguish between the defense attorney and the prosecutor. They tested at the same level as mentally ill adults found not competent to stand trial.
In another study, Woolard found that many parents don’t have accurate knowledge about how the legal system works and that parents and juveniles had very different ideas about who gets to make decisions about things such as whether a juvenile talks to police.
“We’re beginning to see the potential for conflict and misunderstanding – and important legal ramifications,” Woolard says.
In Colorado, both juvenile and adult court can address a defendant’s competency but generally only as it relates to mental health concerns, says Karen Ashby, Denver’s chief juvenile court judge.
“There’s a movement afoot nationally to say we should rethink whether to say developmental issues are not a consideration for kids being tried as adults,” Ashby says. “But I don’t know anyone in Colorado who is moving toward such a change at this time.”