What does "Locard’s exchange principle" state?

Locard's exchange principle is a fundamental concept in forensic science, stating that the perpetrator of a crime will bring something into the crime scene and leave with something from it. This signifies that whenever a crime is committed, there is an exchange of materials between the suspect and the crime scene. This principle underscores the idea that evidence is created through interactions with the environment, meaning that forensic analysts can often find physical evidence linking a suspect to a crime scene, such as fingerprints, hair, fibers, or other trace evidence.

This principle is crucial in crime scene investigations because it establishes the basis for why physical evidence is vital for solving crimes. It emphasizes the relationship between the criminal, the victim, and the scene, illustrating that an individual cannot be present at a scene without leaving some form of trace behind. Understanding Locard's exchange principle helps investigators gather and analyze evidence effectively, leading to more accurate conclusions in forensic investigations.