1. Introduction
Recent insights from neuroscientific studies on brain maturation emphasize the view that young adults are a distinct group with different needs compared to children and adults. Evidence from these studies shows that the frontal lobes of the brain continue to develop into the mid-twenties (Prior et al., 2011). It is assumed that this part of the brain deals with the regulation of impulses that may lead to criminal behaviour (see e.g., Monahan, Steinberg, Cauffman, & Mulvey, 2009; Steinberg, 2013; Strang, Chein, & Steinberg, 2013). A second compelling neuroscientific insight is that great variation between individuals exists in the rate in which this maturation occurs (Braams, van Duijvenvoorde, Peper, & Crone, 2015). These neuroscientific insights are helpful to better understand criminal behavior and how to deal with delinquent young adults in the criminal justice system. First, young (adult) offenders account for a disproportionate amount of crimes, a phenomenon that is widely known as the age-crime curve (Farrington, 1986). Second, individual variation exists in continuing criminal careers or desistance from it during young adulthood. For those who continue their criminal career and get into contact with the criminal justice system, it is seen as a challenge to motivate and engage them in any intervention as part of their sentence. Third, amongst psychosocial findings, neuroscientific insights raise the question whether immaturity can be listed as a mitigating factor in judicial decision-making.