This report provides a comprehensive overview of the UK's criminal justice system. It begins with an introduction to the system and its key components, including law enforcement, courts, and prosecution services. The main body delves into the different types of law, such as common law, statutes, civil law, and criminal law, outlining their purposes and consequences. The report also explores key legal principles like Actus Reus, Mens Rea, concurrence, causation, and harm. It then examines the hierarchy of courts in the UK, including the Supreme Court, Court of Appeal, High Court, Crown Court, and Magistrates' Court, detailing their functions and jurisdictions. The report also discusses the appeals process and the various public services and organizations involved in the criminal justice system, such as the Crown Prosecution Service, police forces, the Ministry of Justice, and Her Majesty's Prison & Probation Services. Finally, the report touches upon the methods used to measure the effectiveness of the criminal justice system, including data collection from the public, victims, and witnesses. This report provides a detailed analysis of the UK legal system.