© Cambridge University Press 2013. Introduction The judgment of the European Court of Human Rights (ECHR) in the case of V v. United Kingdom concerned the trial of an eleven-year-old boy (with his co-accused, considered in T v. United Kingdom) for the notorious murder of a two-year-old boy, James Bulger, in Liverpool, England, in 1993. The case made headlines around the world for various reasons: its shocking facts, the public outrage and anger that erupted around the murder and the trial, and the wave of punitive measures introduced as a response by the United Kingdom government. From the perspective of ECHR case law, the judgment, which found that the boys’ trial was unfair and contrary to Article 6 of the Convention, was ground-breaking. Although it was not the first time the Court had addressed the application of Article 6 to children, the judgment broke new ground in its development of the concept of ‘effective participation’ of children in criminal proceedings against them. Mirroring Article 12 of the Convention on the Rights of the Child, which guarantees the right of the child to be heard in matters that affect him/her, the judgment makes a unique contribution to our understanding of children’s treatment by the criminal justice system. The judgment raised awareness about a range of issues in youth justice. In particular, V v. United Kingdom cast important light on the role of the media and publicity in the trial of children, and raised concern about the harm that can be caused by the trial of children in adult court. It stressed the need to ensure that children in the criminal justice system are treated in a manner that takes full account of their age, maturity and intellectual and emotional capacities, and it linked this clearly to the child’s right to understand and participate in proceedings against him/her. These issues have been developed in subsequent international instruments like the Council of Europe’s Guidelines on Child-Friendly Justice, and the Strasbourg court’s findings are echoed in recent criminology and neuroscience research.