This article addresses our endeavors and experiences conducting a Randomized Controlled Trial (RCT) to evaluate a promising aftercare intervention in the Netherlands. New Perspectives Aftercare Program (NPAP) is an intensive reentry program for serious juvenile and young adult offenders, aged 16 to 24, starting in the last phase of their detention or secure care and lasting for 9 months. Implementing the experimental study was a challenge, because it covered both the juvenile and adult justice system, with offenders receiving aftercare mandated under criminal and civil law, resulting in complex referral pathways complicating the system and moment of randomization. Other matters were related to resistance to random assignment and unforeseen conflicts between administrative and evaluation priorities of the different stakeholders, such as the city council and youth care organizations. Our experiences may be helpful to other researchers who encounter similar problems to fruitfully conduct experimental research in criminal justice settings.