NOVEMBER 7, 2012WARM-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.
PHYSICAL EVIDENCE
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 salivaDocumentsDrugsExplosivesFibersFingerprintsFirearms and ammunitionGlassHairImpressionsOrgans and physiological fluids
PaintPetroleum productsPlastic bagsPlastic, rubber, and other polymersPowder residuesSoil and mineralsTool marksVehicle lightsWood 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:
BIOLOGICAL IMPRESSION MANUFACTURED
IDENTIFICATION
The process of determining a substance’s physical or chemical identity.
COMPARISON
The process of determining whether two or more objects have a common origin.
INDIVIDUAL CHARACTERISTICS
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
CLASS CHARACTERISTICS
Properties of evidence that can be associated only with a group and never with a single source
CRIME SCENE RECONSTRUCTION
Figure 3–9 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 3–8 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 victim’s bullet wound with the bullet hole present in the glass pane.