What principle states that criminals leave and take evidence at crime scenes?

Locard's Principle, formulated by Dr. Edmond Locard, asserts that "every contact leaves a trace." This means that whenever a perpetrator visits a crime scene, they will invariably leave behind evidence while also taking some with them. This principle serves as a foundational concept in forensic science and criminal investigation, emphasizing the importance of trace evidence and how it can link a suspect to a crime.

For example, if a suspect enters a residence, they may leave behind fingerprints or hair, while also potentially taking something like a piece of jewelry or fibers from the scene. This reciprocal relationship between suspects and crime scenes is critical for investigators as it helps establish connections between a suspect and a crime.

In understanding this principle, law enforcement officers are equipped with a crucial tool for collecting evidence and building a case against an individual. The focus on physical evidence left behind or taken from a crime scene allows for greater accuracy in criminal investigations and helps reinforce the validity of forensic evidence in legal proceedings.