Whenever a person is murdered, the police initiate a thorough investigation into the crime, crime scene and friends and family of the victim. Each aspect of the investigation is important, but often it is the physical evidence of the crime that catches and convicts the criminal.
Criminal investigations involve a variety of scientific fields and complex instrumentation.
Chemistry, physics and biology are used in combination when detectives and laboratory technicians investigate a murder. Special tests include determining blood alcohol levels, using chemicals to make almost invisible blood stains very visible and typing blood to identify possible suspects. Geometry and trigonometry help the investigators evaluate critical evidence like the angles of lethal blows and the trajectory of bullets. The tools of criminal investigations include computers, sophisticated photographic equipment, lasers, microscopes and other scientific equipment. The study of both forensics and criminology require excellent observation skills and objectivity.