This Casebook is one of the deliverables of the European Commission's funded project TRIIAL TRust, Independence, Impartiality and Accountability of judges and arbitrators safeguarding the rule of Law under the EU Charter. It presents a selection of case law from almost 200 cases collected by beneficiaries involved in the project; cases that were identified in the course of discussions between judges and legal practitioners that participated in the TRIIAL events and through desk research on the evolution of the standard of judicial independence, impartiality, and accountability on the European continent and, specifically, within the context of the European Union.The attempt was to illustrate both the activities of pan-European courts engaged in addressing systemic pan-European questions and problems occurring on a more local scale within specific EU jurisdictions. It is, in fact, within the legal system of the European Union that evolutionary and, arguably, revolutionary developments took place, allowing all of its Member States (and other states parties to ECHR) to revisit the rules behind the fulfilment of the mandate of judges, wielders of the judicial power in Western democracies. Such developments offered a new perspective on the use of the European Union based judicial interaction techniques as tools for the assessment and improvement of the systemic arrangements providing for the position of a judge and the ability to fulfil her function both within a given legal system and in cross-border situations. In this Introductory section we present the Rationale of this Casebook and information about its Structure and potential use.