The purpose of this book is to bring the reader to an intermediate level of attainment in the main branches of investigation. From this point he can proceed to specialized fields of crime detection or non-criminal inquiry. It is the object of the book to introduce the student to investigative work in such a way that he will learn what is meant by a complete investigation and acquaint himself with the proofs of the most important crimes, and become familiar with the employment of technical methods and services available to him. The book is intended as a presentation of the foundations of investigation. An attempt has been made throughout to lay a sufficiently broad groundwork to enable the reader to pursue his further studies rather than to carry any single topic to exhaustive completeness. The presentation is directed to the beginning student of the art of investigation. The text throughout is addressed to the investigator, a term chosen in preference to such titles as detective and agent because of its more general nature. Thus the ideas and precepts have been arranged to practical application by a city detective or plainclothesman, a private investigator, or a federal agent. Military personnel may find the work particularly useful in view of the fact that many of the paragraphs devoted to legal matters reflect the principles of the Uniform Code of Military Justice. The seventh edition continues the tradition of concentrating on the essential elements of a criminal investigation. Among the changes for the new edition, some of the new topics introduced include stalking, carjacking, home invasion robbery, drug-facilitated rape, electronic evidence collection, clandestine laboratories, and the CODIS identification system. There has been an extensive revision of the narcotics chapter to reflect the changing patterns of illegal drug use. Ecstasy, methamphetamine, dissociative anesthetics, Ritalin, oxyContin, inhalants, and anabolic steroids are some of the more commonly abused drugs that are treated here for the first time.