This book investigates the theory and practice of the right to confrontation, the right of an accused person to examine witnesses against him. The book tackles the crucial question of what values and interests should allow incursions into this fundamental right. A conceptual analysis is developed in order to define the concept of testimonial evidence and to establish three categories of declarants: the absent, anonymous, and vulnerable witnesses. U.S. law on the Sixth Amendment of the Federal Constitution and ECHR jurisprudence on Article 6 of the European Convention are discussed in an attempt to develop a supra-national approach to confrontation. The book then moves on to provide a comparative study of the right to confrontation, drawing on the rules of criminal procedure and evidence of Italy, France, England, and Wales.