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
require excellent observation skills and objectivity. The first official who arrives at the crime scene works quickly to seal off the area and preserve the scene as much as possible. Usually no one enters until the field investigator has had a chance to look about and collect every piece of evidence like hair and fiber samples, pieces of clothing or other personal belongings. Only then do other police officers or medical personnel enter the area. When a piece of evidence is found at the scene of the crime, investigators are always careful to keep it in a labeled and sealed package until it can be safely stored in the police vault. It is only opened again when the case goes to court. This kind of evidence care-taking is especially important in drug-related cases when drugs are seized. Regardless, it is against the law to tamper with any kind of evidence.
Scene investigators are always on the lookout for finger and foot prints. These clues can be essential in identifying or eliminating murder suspects.
- Plaster of Paris
- Hair spray
1. Divide your class into investigation and criminal teams. Have the "criminals" go outside and make footprints in some soft soil. Have some people wear their shoes and have others take them off. 2. While the "criminal" team is outside, the "investigation" team should mix the Plaster of Paris with water. Try to keep the consistency thick so that the impressions can retain small details. 3. The "investigators" should then locate the "criminals" footprints and spray each with the hair spray. This will keep the soil in place when you begin to make your mold. 4. Pour the Plaster of Paris into the prepared footprints. Pour slowly from the sides and be careful not to disturb the area. 5. Allow the mold to set. 6. Have the investigation team try to match the footprints to the correct member of the "criminal" team.