The initial actions taken by the first officer in a homicide case may determine whether or not there will be a successful homicide investigation. It is imperative that first officers adhere to recognized and standard operating procedures to assure a professional and potentially successful conclusion. This article describes and reviews the critical and essential steps and duties a first officer must perform when arriving upon a homicide crime scene. The first officer has three primary duties: (1) determine if the victim is alive or dead; (2) apprehend the perpetrator, if possible or give the appropriate notification if the perpetrator is escaping; and (3) safeguard the scene and detain witnesses and suspects. Even though detectives and criminal investigators will conduct the formal investigation, the first officer has the responsibility of initiating the investigation. Practical rules of procedure are provided as a guide in initiating a professional homicide investigation. The article concludes with a basic five-step approach, ADAPT, that a first officer should be aware of when confronted or responding to a homicide crime scene: Arrest or apprehend the perpetrator; Detain and identify witnesses and/or suspects; Assess the crime scene; Protect the crime scene; and Take notes.