Book excerpt: First Unit Responder: A Guide to Physical Evidence Collection for Patrol Officers is a training guide and reference for patrol officers and criminal investigators, who conduct preliminary investigations of crime scenes, to aid in identification, collection, and booking of physical evidence. Written by a veteran of 24 years of law enforcement, the book stresses the importance of understanding the critical nature of physical evidence and preservation of the crime scene as part of the case against a criminal defendant. This book is an important tool for police academies that train recruits and veteran patrol officers, as well as for students of criminal justice who seek guidelines for proper collection and handling of physical evidence.