The law of criminal evidence has a cohesion of principles which requires its separate treatment. Like any procedure for determining the truth about events, it has to be evaluated by reference to its structure and its general principles. This introductory textbook on the law of criminal evidence explains that its central feature is the continual search for a balance between competing demands, the first of which is the desire to discover the truth. This desire assumes a special significance in the criminal trial where it reflects the powerful public interest in bringing offenders to justice. The second principle is the protection of the innocent from conviction, which finds expression in several rules such as the requirement of proof beyond reasonable doubt and the rule excluding evidence which may create prejudice against the second. The third principle is that of maintaining standards of propriety in the criminal process. The latter underpins the privilege against self-incrimination, affects the procedure for obtaining confessions and influences the court's attitude to improperly obtained evidence.