Teenagers are not fully developed; studies have shown that their brains aren't as capable of moral reasoning and impulse control as adults in their early or mid-20s. They don't have as much mastery over their environment as adults do, which contributes to their susceptibility to peer pressure and other potentially destructive influences.
There is also more hope of rehabilitating young offenders. Those are among the reasons that the Supreme Court last year insisted, that punishment of minors must be properly "graduated and proportioned."
Yet, the report notes, citing figures that are a few years old, there are some "100,000 youth who are placed in adult jails and prisons each year." When minors are thrown into adult jails and prisons, often simply to await trial, they don't get the structure and education necessary for growth or rehabilitation. They are also extremely vulnerable to harm. "More than any other group of incarcerated persons," a federal panel reported in 2009, "youth incarcerated with adults are probably at the highest risk for sexual abuse."
Since 2005, 23 states have changed policies to reflect these considerations, often with wide bipartisan support. States such as Texas have made it easier for state boards or judges to place minors in juvenile detention, even if they are awaiting trial in adult court. States such as Illinois have given juvenile courts jurisdiction over offenders up to 18 years of age. And states such as Arizona have offered minors more recourse to challenge their diversion into adult court.
Federal policy deserves at least some credit for this trend. Activists have pointed out that these sorts of reforms will help states comply with the 2003 Prison Rape Elimination Act. The law obliges states to keep minors away from adults and to avoid inflicting the hell of solitary confinement on them. If states don't comply, they could lose some federal funding.
It should not take that sort of federal stick, though, to encourage states to continue seeking the right balance between punishing crime and avoiding penalties that are overly harsh, ineffective or both.