A central principle under which the U.S. criminal justice system holds people accountable is the capacity to decipher right from wrong and to understand the consequences of one’s actions. Adolescents are in-between—not adults, not children. They certainly understand right and wrong, but their cognitive capacity is not as developed, nor their reasoning as sophisticated, as adults. However, over the years, many courts have tried teens as adults or enacted long sentences for more serious crimes. Is this practice fair and just based on what we now know about the teenage brain? What criminal responsibility do adolescents have?