Evidence is defined as anything that can be used in a court of law. The evidence may be direct, real or demonstrative, or indirect. An officer responding to a crime must safeguard the scene so valuable evidence is not destroyed. A declaration from a badly injured or dying victim may be needed. Major tasks of a detective completing a criminal investigation are delineated, and the importance of taking good, clear photographs of the undisturbed crime scene is emphasized. The securing of all immovable evidence, such as footprints and fingerprints, and movable evidence, such as firearms or debris, is explained. The importance of preparing for witness-stand testimony is discussed, taking into account the officer's appearance, clear diction, and direct answers. Photographs are supplied.