The purpose of crime scene investigation is to help establish what happened (crime scene reconstruction) and to identify the responsible person. This is done by carefully documenting the conditions at a crime scene and recognizing all relevant physical evidence. The ability to recognize and properly collect physical evidence is oftentimes critical to both solving and prosecuting violent crimes. It is no exaggeration to say that in the majority of cases, the law enforcement officer who protects and searches a crime scene plays a critical role in determining whether physical evidence will be used in solving or prosecuting violent crimes.