Crime scene investigation

"Where ever he steps, what ever he touches and what ever he leaves, even unconsciously. Will serve as silent witness against him. Not only his fingerprints or his footprints, but his hair, the fibers from his clothing, 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 its interpretation can error. Only human failure to find, study and understand it, can diminish its value." Harris vs United States, 331 US 145, 1947