Forensic science, one of the most important aspects of the criminal justice system, commonly utilizes ultraviolet (UV) and violet light as an integral part of crime scene investigation. Because UV analysis is non-destructive, it is typically the first choice when examining biologically contaminated evidence. Body fluids, such as saliva or perspiration, give off fluorescent light when illuminated with a UV light source. Using this concept, forensic science technologies employing UV light are able to detect bite marks on skin, shoe impressions on tile, bloodstains, and more. Forensic technicians have also used this technology to detect the presence of illegal substances or explosive residues.