'Crossover Children' are young people (14-17 years) who cross from state care and protection to serious and recidivist offending. The report reviews research and statistics both past and present, both nationally and internationally related to this population. It includes the voice of stakeholders both in New Zealand and the USA, from the judiciary, government agencies, and academics and researchers with an interest in this field. It incorporates insights from people working on the ground with crossover youth in marae communities. It also explores the potential of the government's integrated data infrastructure (IDI) to access information important for this work.