The current study examined the relationship between knowledge of adolescent brain development and attitudes about juvenile competency, responsibility, likelihood to recidivate, and rehabilitative capacity. In addition, it examined what factors—a juvenile's age, the type of crime committed, or the immediacy of the crime—influenced participants' perceptions. Participants displayed some knowledge of adolescent brain development and social maturity, and tended to see adolescents as not ready, emotionally or psychologically, to handle the proceedings of adult court or a jury trial. However, a delay in criminal behavior (immediate vs. next morning) and type of victim (targeted vs. random) heavily influenced ratings of responsibility, likelihood to recidivate, and rehabilitative capacity. Implications for jury decision making and public policy are discussed.