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The Crime Scene

The Crime Scene. Principle of Exchange. Dr. Edmond Locard , director of the world’s first forensic lab (1910, Lyon, France), established the idea of the exchange principle; namely that:

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The Crime Scene

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  1. The Crime Scene

  2. Principle of Exchange Dr. Edmond Locard, director of the world’s first forensic lab (1910, Lyon, France), established the idea of the exchange principle; namely that: • When a person comes in contact with an object or another person, a cross-transfer of physical material can occur. • Study of the material can determine the nature and duration of the transfer.

  3. Types of Evidence • Statements of a witness in court would be directevidence. • Indirect or circumstantial evidence, such as a fingerprint (physical evidence) or blood or hairs (biological evidence), would imply something, and is called trace evidence.

  4. Trace Evidence • Type of Circumstantial evidence • Physical transfer of material • Examples: • Hair • Fingerprints • Soil • Blood • Kleenex • Fiber • Glass • Paint chips

  5. Class Evidence • Narrows an identity to a group of persons or things • Cannot specify a single person • Only excludes people that do not fit the category • Examples: • Blood types • Hair color • Common fibers • Shoe prints

  6. Individual Evidence • Narrows identity to a single person or thing • Examples: • DNA • Complete fingerprints (not partials) • Tool marks • Anything torn or broken and left at the scene

  7. The Five S’s of Crime Scene Investigation • Secure the scene. • Separate the witnesses. • Scan the scene. • Sketch and photograph the scene. • Search for and collect evidence.

  8. Securing the Scene • The most important job at a crime scene • Performed by the first officer at the scene, called the first responder • Safety of all individuals is first priority • Preservation of evidence is second • Finally record the scene

  9. Separate the witnesses • Separation prevents them talking to each other • Each witness will be asked about the crime scene and what they observed

  10. Scan the Scene • Determine if and where photos should be taken • Determine if there may be a secondary crime scene • Person killed at a party (primary scene) • Dumped in a lake (secondary scene)

  11. Sketching the Scene • First is a Rough Sketch done at the scene • Must be accurate and to scale • Note body, evidence, doorways, windows, walls, trees, cars, and movable objects • Distances should be measured and recorded • Case number, date, location, and time should also appear on the sketch

  12. Photographing the Crime Scene • Photograph: • All evidence • Doors and windows • Anything out of the ordinary

  13. Searching and Collecting Evidence • Must be properly packaged, sealed, and labeled • Dry evidence - placed in a paper bindle, put into a plastic bag, sealed with tape, labeled • Wet evidence - placed in a paper bag to allow drying, then treated like dry evidence • When bag is sealed, person must sign their name across the seal

  14. Chain of Custody • Must be attached to evidence container • Starts with person who finds evidence • The next person to use or analyze the evidence must fill out a label • Ensures evidence is handled correctly • If it is not handled correctly, can be traced to who’s responsible

  15. Packaging the evidence • Crease a clean paper and place the evidence in the X position (as shown above). • Fold in the left and right sides, and then fold in the top and bottom. • Put the bindle into a plastic or paper evidence bag affixing a seal over the opening. • Write your name on the seal.

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