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.