A brief blurb about antisocial personality disorder, coauthored by Steinberg, who is a leading (if not the leading) mental health expert in the country on youth and violence.

Another reason to use caution before trying kids as adults

It is widely acknowledged that involvement in delinquent and criminal behavior increases through adolescence, peaking somewhere around age 16 and declining thereafter (Piquero, 2008; Piquero et al., 2001). Although a small number of youths persist in antisocial behavior across this developmental period, the vast majority of antisocial adolescents desist from criminal behavior as they enter adulthood (Laub & Sampson, 2001; Piquero, 2008; Sampson & Laub, 2003). Psychological theory suggests that part of the reason for this age-related desistance from crime is that individuals mature out of antisocial behavior. Specifically, desistance from antisocial behavior is viewed as the product of psychosocial maturation, including increases in the ability to control impulses, consider the implications of one's actions on others, delay gratification in the service of longer term goals, and resist the influences of peers (Cauffman & Steinberg, 2000; Steinberg & Cauffman, 1996; Monahan, Steinberg, Cauffman, & Mulvey, 2009). To date, however, little research has examined how psychological maturation is associated with desistance from antisocial behavior, largely because psychological maturation during young adulthood has received relatively little attention from developmental psychologists. Recent research indicating protracted maturation, into the mid-20s, of brain systems responsible for self-regulation, however, has stimulated interest in charting the course of psychosocial maturity beyond adolescence.

The mostly widely cited theory regarding psychological contributors to desistance from antisocial behavior during the transition to adulthood has been advanced by Moffitt (1993, 2003). She distinguishes between the vast majority (90% or more, depending on the study) of individuals whose antisocial behavior stops in adolescence ("adolescence-limited offenders") and the small proportion of those whose antisocial behavior persists into adulthood ("life-course persistent offenders"). It is important that Moffitt suggests that different etiological factors explain these groups' involvement in antisocial behavior. Adolescent-limited offenders' involvement in antisocial behavior is hypothesized to be a normative consequence of their desire to feel more mature, and their antisocial activity is often the result of peer pressure or the emulation of higher status age mates. In contrast, when individual antisocial behavior persists into adulthood, it is thought to be rooted in early neurological and cognitive deficits that, combined with environmental risk, lead to early conduct problems and lifelong antisocial behavior.

Goldweber, A., Dmitrieva, J., Cauffman, E., Piquero, A. R., & Steinberg, L. (2011). The development of criminal style in adolescence and young adulthood: Separating the lemmings from the loners. Journal of youth and adolescence, 40(3), 332-346.

Here is a truism that most diagnosticians understand. Most people age out of the constructs that we call "personality disorders"—some do after their teen years (antisocial personality disorders); other do in their 30s and 40s (esp borderline and histrionic personality disorders). They aren't enduring but often represent the intersection between temperament, difficult environmental factors and vulnerabilities that are normative parts of psychosocial development.

In other words, most of those "antisocial" kids,who are largely from lower socioeconomic classes (yes, there is a huge amount of diagnostic bias and medicalization of what is in fact a social issue), given the opportunity— will develop into stable adulthood. So giving 16 year olds adult sentences preempts the often normative trajectory into a more stable maturity. In fact, the system is directly interfering with psychosocial goals.

And for those of you wondering, antisocial personality disorder replaced the category of sociopath in the more recent editions of the DSM.