This document provides an overview of criminal investigation. It defines criminal investigation as the process of discovering, collecting, and presenting evidence to determine what happened and who is responsible for a crime. The goals of criminal investigation are to determine if a crime has been committed, legally obtain information to identify the responsible person, arrest the suspect, recover evidence, and present the case to the prosecutor. An effective investigation follows a logical sequence, legally obtains all evidence, interviews all witnesses and suspects, thoroughly develops all leads, and accurately records all case details.