When does a human brain fully develop? The answer to this question might mean life or death for adolescents who have been charged with serious crimes like homicide.

According to Laurence Steinberg, PhD, from Temple University, an expert in the adolescent developmental psychology, the brain develops in parts rather than whole. A teenager's brain might be fully developed in some areas but it lacks self-regulation.

A recent example of the dilemma that courts face when awarding a sentence to a juvenile was in the "Miller v. Alabama" case. The Supreme Court ruling said that even in crimes that involve a homicide, a life sentence without parole for juveniles is unconstitutional.

The Supreme Court ruling had cited American Psychological Association's amicus brief explaining the current research.

"The Supreme Court decision that eliminated mandatory life without parole sentences for juveniles in homicide cases was certainly a step in the right direction but might have gone further as it is still possible for an adolescent to receive a sentence of life without parole, even though it isn't mandatory," Steinberg said.

Steinberg said that by adolescence, the brain develops intellectually. But the brain isn't self-regulated until many more years. The idea of regulating one's action fully evolves during late adolescence or even in early adulthood.

"In other words, adolescents mature intellectually before they mature socially or emotionally, a fact that helps explain why teenagers who are so smart in some respects sometimes do surprisingly dumb things. From a neuro-scientific standpoint, it therefore makes perfect sense to have a lower age for autonomous medical decision-making than for eligibility for capital punishment, because certain brain systems mature earlier than others," Steinberg said in a news release.

Brain scans have shown that the reward region of the brain is highly activated during adolescence, even more than it is activated during childhood, Steinberg said.

"Heightened sensitivity to anticipated rewards motivates adolescents to engage in risky acts, such as unprotected sex, fast driving or drugs when the potential for pleasure is high. This hypersensitivity to reward is particularly pronounced when they're with their friends," Steinberg said.

The results of the research can be interpreted in making policies that will keep teens in check to policies that will protect teens from emotional harm.

"Some will use this evidence to argue in favor of restricting adolescents' rights, and others will use it to advocate for policies that protect adolescents from harm. In either case, scientists should welcome the opportunity to inform policy and legal discussions with the best available empirical evidence," Steinberg added. 

Dr. Steinberg will be presenting his research at the American Psychological Association’s 120th Annual Convention.