Physical%20Evidence3

Physical%20Evidence3 - 8/11/10 Physical Evidence Physical...

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8/11/10 1 Physical Evidence Physical evidence cannot be wrong; it cannot perjure itself; it cannot be wholly absent. Only its interpretation can err. Only human failure to find it, study and understand it, can diminish its value. Presiding Judge, Harris v. U.S., 331 U.S. 145 (1947) Concentrate on what cannot lie. The evidence. Gil Grissom, CSI Las Vegas Well, if you are going to break the law, you should know the law. Also Gil Grissom, CSI Las Vegas
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8/11/10 2 Locard’s Exchange Principal: Whenever two objects come into contact with one another, there is an exchange of materials between them. What are we talking about? • Common Types • Identification and collection • Comparison –Individual vs. Class Characteristics • Crime-Scene Reconstruction
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8/11/10 3 Some Examples… Biological or natural origin – Blood, semen, saliva Found? fabric, cigarette butts, stains – Hair – both human and animal – Fingerprints – visible and latent – Organs and physiological fluids – detect drugs and poisons – Soil and minerals – embedded in shoes, material connected to crime – Wood and other vegetative matter – sawdust, shavings, packing material – Insect larvae 1 in 6 women and 1 in 33 men are sexually assaulted Insect Larvae
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8/11/10 4 Material of man-made origin – Drugs – bulk and trace levels – Explosives – chemicals and initiators – Fibers – natural and synthetic – Firearms- ammunition, gunshot residue – Glass – hit and run, break and enter – Paint – hit and run, transfer evidence – Petroleum Products – arson, lubricants – Plastics – linked to objects found on suspect – Documents – notes, records, obliterations Impression Evidence Impressions – Tool marks – crowbars, firing pins – Tear marks – tapes, plastic bags – Document impressions – writing – Tire prints, shoeprints
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8/11/10 5 Archaeology or CSI??? Process a crime scene vs examine a site for historical record of human activity – Snapshot of past activity – One way “careful dissection” – once an item is moved it will never exist in the same way. Must record the provenience (location) and context (relationship to other items) Important differences Safety – many of these scenes may be very hazardous – Inhalation hazards – smoke, solvents, gases, asbestos – Booby traps - bombs, electrical fixtures, light switches – Disease hazards - AIDS, hepatitis, TB, anthrax – Physical hazards – sharps, falling objects, spills – Presence of perpetrator
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8/11/10 6 Universal precautions for blood borne hazards Blood borne hazards – Vaccine – Barrier protections – gloves, coveralls, shoe covers – Change gloves when compromised – Eye and face protection – Place sharps in appropriate containers – No eating, drinking or use of cosmetics – Wash hands when done – Decontaminate equipment with 1:10 bleach or rubbing alcohol Chemical and Physical Safety Eye protection – goggles or face shield
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Physical%20Evidence3 - 8/11/10 Physical Evidence Physical...

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