This text presents the fundamentals of criminal investigation and provides a sound method for reconstructing a past event (i.e., a crime), based on three major sources of information — people, records, and physical evidence. Its tried-and-true system for conducting an investigation is updated with the latest techniques available, teaching the reader new ways of obtaining information from people, including mining the social media outlets now used by a broad spectrum of the public; how to navigate the labyrinth of records and files currently available online; and fresh ways of gathering, identifying, and analyzing physical evidence.