By the 2nd decade of the study, foundations were being laid for work that ultimately distinguished between children with early-onset and persistent antisocial behaviour versus those whose antisocial behaviour began in adolescence. These two groups have different aetiologies and require different policy responses. This distinction has now been enshrined in diagnostic taxonomies, and according to the Principal Youth Court Judge (Andrew Beecroft), has profoundly influenced judicial practice in New Zealand. Further afield, this work contributed to the Amicus Brief that led to the overturning of the death penalty for youth under the age of 18 in the United States of America. The impact and significance of this research were recognised in 2007 when Terrie Moffitt was awarded the Stockholm Prize.
