Municipal Police Officers' Education and Training Commission (MPOETC) Act 120 Practice Exam

Which principle states that someone will always leave something behind at a crime scene?

1. Affidavit principle

2. Locard exchange principle

3. Evidence continuity principle

4. Chain of custody principle

The correct answer is: Locard exchange principle

The principle that someone will always leave something behind at a crime scene is known as the Locard exchange principle. This principle asserts that whenever a person comes into contact with an environment, they will leave behind traces of their presence while also taking something from that environment. This can manifest as physical evidence such as hair, fingerprints, or fibers, which can be crucial in criminal investigations. The Locard exchange principle is foundational in forensic science because it highlights the importance of collecting and examining evidence at a crime scene. It reinforces the idea that no one can enter or exit a crime scene without altering it in some way, either by leaving behind evidence or taking evidence with them. In contrast, the other principles mentioned, such as the affidavit principle, evidence continuity principle, and chain of custody principle, pertain to specific legal and procedural aspects of handling evidence rather than the inherent relationship between individuals and their surroundings at a crime scene.