Graham v. Florida

Adolescents have a diminished capacity for self-regulation and impulse control relative to adults; the neural systems supporting cognitive control and behavioral inhibition mature gradually across adolescence and do not reach adult levels until the late teens to early twenties.

Adolescent personality and character are still forming and are not reliable indicators of fixed adult character; most adolescents who engage in antisocial behavior, including serious offending, desist as they mature, so adolescent conduct is a poor predictor of irretrievable depravity.

Adolescents weigh risks and rewards differently from adults: a reward-sensitive socio-emotional system matures earlier than the cognitive-control system, producing heightened reward-seeking, a weaker orientation to the future, and steeper discounting of delayed consequences during adolescence.

The structural maturation of the human brain -- including cortical gray-matter thinning and continued development of white-matter connectivity in regions that support cognitive control -- continues throughout adolescence and into the early-to-mid twenties, later than the maturation of many other organ systems.

Structured, developmentally-appropriate interventions can, on average, reduce reoffending among juveniles; as a group, adolescents are responsive to rehabilitation -- though effects are modest and depend strongly on the type of program, the targeting of higher-risk youth, and the quality of implementation.