ABSTRACT
Dr. Edmond Locard, a physician and lawyer, was the head of the Criminal Investigations Department (CID) in the French city of Lyon, one of the rst laboratories for forensic science. In 1910, Locard stated the basic principle “every contact leaves a trace”—any action performed leaves behind traces, which serve as a silent witness to that action. This refers not only to a ngerprint or a hair but also to a scratch on the skin, clothing bers, paint chips, and more. These are not affected by forgetfulness or excitement-these are concrete evidence. Physical evidence cannot be wrong, it cannot perjure itself or disappear; it is only humans’ incompetence in searching and nding evidence which can thwart the ability to use and rely on it.
