What is a common practice for establishing an outer perimeter at a crime scene?

Deploying patrol units at strategic locations is a fundamental practice for establishing an outer perimeter at a crime scene. This method is crucial for maintaining the integrity of the scene and ensuring that unauthorized individuals do not enter. The presence of patrol units helps to control access points, thereby preventing contamination of potential evidence and preserving the area for investigators.

By placing officers at key positions around the crime scene, law enforcement can effectively monitor the perimeter, maintain safety for both the public and those involved in the investigation, and facilitate a smooth flow of information and movement as the investigation progresses. This practice not only serves to secure the scene but also helps establish a clear boundary for both the crime scene and the context in which the crime occurred.

In comparison, while using caution tape to block access is also important in marking the scene, it does not provide the active control that deploying patrol units does. Interviewing witnesses and collecting evidence are critical tasks but occur after the perimeter is established and do not contribute directly to the initial phase of securing the crime scene.