What does Locard's theory state about the interaction between individuals and locations?

Locard's theory, often referred to as "Locard's Exchange Principle," posits that whenever an individual comes into contact with another person or object, there is an inevitable exchange of materials. This means that the criminal always leaves behind something at the scene and takes something away with them. This foundational concept in forensic science emphasizes the significance of trace evidence—such as hair, fibers, fingerprints, and other small materials that can link a suspect to a crime scene or victim.

This principle illustrates how the environment interacts with the individuals who occupy it, providing critical information for investigators to reconstruct events and affirm connections in a case. The other options do not accurately represent Locard’s principle. For instance, noise levels, blood evidence, and witness reliability do not encapsulate the core idea of evidence exchange that Locard's principle emphasizes. Understanding this principle is essential for grasping how forensic evidence can establish links between suspects and crimes.