High Quality Content by WIKIPEDIA articles! In forensic science, 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 as forensic evidence.Dr. Edmond Locard (13 December 1877 – 4 May 1966) was a pioneer in forensic science who became known as the Sherlock Holmes of France. He formulated the basic principle of forensic science: "Every contact leaves a trace". This became known as Locard`s exchange principle. Paul L. Kirk expressed the principle as follows: