NOVEMBER 7, 2012 WARM-UP: STANDARD-SFS1b. Distinguish and categorize physical and trace evidence. EQ: How is physical evidence analyzed? Sit quietly, and I will put up an observation picture in just a minute. What evidence can be found at a crime scene? Brainstorm with your group to come up with a list of evidence you might find at a crime scene. Blood, semen, and saliva Documents Drugs Explosives Fibers Fingerprints Firearms and ammunition Glass Hair Impressions Organs and physiological fluids Paint Petroleum products Plastic bags Plastic, rubber, and other polymers Powder residues Soil and minerals Tool marks Vehicle lights Wood and other vegetative matter Biological Evidence Impression Evidence Manufactured Evidence Evidence that comes from living material Evidence that makes markings, prints, tracks, and impressions Evidence that is man-made Categorize the evidence as the following: BIOLOGICALIMPRESSIONMANUFACTURED The process of determining a substances physical or chemical identity. The process of determining whether two or more objects have a common origin. Properties of evidence that can be attributed to a common source with an extremely high degree of certainty Individual Characteristics Examples: the matching ridge characteristics of two fingerprints the comparison of random striation markings on bullets or tool marks the comparison of irregular and random wear patterns in tire or footwear impressions the comparison of handwriting characteristics the fitting together of the irregular edges of broken objects in the manner of a jigsaw puzzle matching sequentially made plastic bags by striation marks running across the bags Properties of evidence that can be associated only with a group and never with a single source Figure 39 Crime-scene reconstruction relies on the combined efforts of medical examiners, criminalists, and law enforcement personnel to recover physical evidence and to sort out the events surrounding the occurrence of a crime. Figure 38 A laser beam is used to determine the search area for the position of a shooter who has fired a bullet through a window and wounded a victim. The bullet path is determined by lining up the victims bullet wound with the bullet hole present in the glass pane.