Private security guards are a necessity at the present time, as a complement of the police departments in order to combat crime and terrorism. Both police forces and private security organizations are greatly helped in their work by the methods of forensic science. Forensic science applies scientific methods to the solving of crimes. These methods include fingerprinting, drug analysis, DNA (Deoxyribonucleic Acid) studies, ballistics, arson and explosive investigations, and studies of glass fragments. Fingerprinting and urine, saliva, or hair analysis for the presence of drugs are essential for the hiring of private security guards, in order to establish their suitability for the position.