load exchange principle

Load’s Exchange Principle Locard's principle holds that the perpetrator of a crime will bring something into the crime scene and leave with something from it, and that both can be used. "Wherever he steps, whatever he touches, whatever he leaves, even unconsciously, will serve as a silent witness against him. Not only his fingerprints or his footprints, but his hair, the fibers from his clothes, the glass he breaks, the tool mark he leaves, the paint he scratches, the blood or semen he deposits or collects. All of these and more bear mute witness against him. This is evidence that does not forget. It is not confused by the excitement of the moment. It is not absent because human witnesses are. It is factual evidence. Physical evidence cannot be wrong, it cannot perjure itself, and it cannot be wholly absent. Only human failure to find it, study and understand it can diminish its value.
It is a concept that was developed by Dr. Edmond Locard (1877-1966). Losar speculated that every time you make contact with another person, place, or thing, it results in an exchange of physical materials. He believed that no matter where a criminal goes or what a criminal does, by coming into contact with things, a criminal can leave all sorts of evidence, including DNA, fingerprints, footprints, hair, skin cells, blood, bodily fluids, pieces of clothing, fibers and more. At the same time, they will also take something away from the scene with them.
Traces of physical materials trace evidence. No matter how minute can tell a story. Trace evidence is factual. Unlike humans, it cannot be confused by the excitement of the moment, and it does not forget. It’s a silent witness that speaks when humans cannot. Physical evidence cannot be wrong, it cannot lie, and it cannot be wholly absent. Only human failure to find it, study and understand it can diminish its value. When a crime has occurred, the goal of a Crime Scene Investigator is to recognize, document, and collect