What should an investigator do first to avoid contaminating evidence?

Securing the scene is the critical first step in avoiding contamination of evidence. By establishing control over the crime scene, investigators prevent unauthorized individuals from entering the area, which could lead to the alteration, destruction, or addition of evidence. This process includes setting up physical barriers, such as tape or cones, and establishing a perimeter to keep potential witnesses and onlookers away.

Once the scene is secured, it becomes significantly easier to document and collect evidence without the risk of it being tampered with. This foundational action is essential in maintaining the integrity of the investigation and ensuring that any evidence collected can be deemed reliable in legal proceedings.

The other actions, such as documenting what is seen, notifying superiors, and waiting for backup, are important but should occur after the scene has been secured to ensure that evidence remains uncontaminated. Each of these subsequent actions relies on the successful initial step of securing the scene.