THE PRINCIPLE OF EXCHANGE. Locard's Principle: "There is no such thing as a clean contact between two objects. When two bodies or objects come into contact, they mutually contaminate each other with minute fragments of material." via things --Physical Evidence---The science and art of profiling crime scenes, and subsequently offenders, from physical and psychological evidence is key to the investigation of a violent serial sex crime for which there is no known perpetrator. The profiling method is based on Locard's Principle of Exchange; anyone who enters the scene both takes something of the scene with them and leaves something of themselves behind----Evidence Dynamics: Locard's Exchange Principle & Crime Reconstruction----Every person who is physically involved in a crime leaves some minute trace of his or her presence, and often takes something away. This is Dr. Edmond Locard's principle of contact, proposed when he began his forensic laboratory in 1910 ----
"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, it cannot be wholly absent. Only human failure to find it, study and understand it, can diminish its value." Professor Edmond Locard(1877-1966)---- Criminalistics and Trace Evidence are both catch-all terms that apply to all types of physical evidence that may be circumstantial evidence in the trial of a case---This guide describes procedures and techniques for the documentation, detection, collection, and preservation of trace evidence from crime scenes, individuals, and items submitted to the laboratory for examination---Criminalistics & Trace Evidence Links----These inexpensive Trace Evidence Collection Kits are designed to assist officers in the proper collection of trace evidence. Each kit contains a total of 12 evidence containers which are suitable for a wide variety of different types of evidence, along with seals to ensure the integrity of the evidence collected.