Criminal Procedure: Constitutional Constraints Upon Investigation and Proof is intended for use in an introductory Criminal Procedure course that focuses on issues generated by the investigative efforts of law enforcement entities. The topics addressed include: searches and seizures, entrapment, confessions, identification procedures, and the exclusionary rules. The Eighth Edition adheres to the practical and flexible approach that has characterized the text from the start. The textual material at the beginning of each chapter and between main opinions is still concise, focused on the foundational essentials that enhance understanding of core concepts. The problems at the end of subsections and chapters, all based on actual federal and state cases, have been updated with some raising novel issues. They serve to expose students to cutting-edge questions. They also furnish opportunities to test comprehension of doctrines by applying them to concrete situations and to refine exam-taking skills. The opinions are limited to those decided by the United States Supreme Court. A core objective of the text is still to present sufficient materials to enable students to gain an appreciation of the richness and complexity of the variety of issues in the field. The Eighth Edition includes edited versions of the most significant opinions handed down since the Seventh Edition was published and incorporates notes that capture the essence of other important rulings. A few significant opinions have been supplanted and now are the subject of summarizing notes. One brief foundational chapter—which addressed the right to assistance of counsel at trial—has been omitted. The foundation is now provided by a substantial note that introduces the following chapter.