Processing the Crime Scene Securing Physical Evidence            http://i.cnn.net/cnn/SPECIALS/2000/columbine.cd/Photos/EN...
What is Physical Evidence?   Any and all objects that can:       establish that a crime has been        committed      ...
Priorities at the Crime Scene   Obtain medical aid for those in need   Arrest the perpetrator   Secure the crime scene ...
Photography   Scene must be unaltered!       If objects are removed,        positions changed, or items        added pho...
Sketches   Rough sketch records       Dimensions of crime scene and        surroundings       Location of each piece of...
Systematic Search Patterns   Spiral search   Grid method   Strip of line search   Quadrant or zone    search          ...
Evidence Collection   Must collect all    possible carriers of    evidence       Clothing          Package each item   ...
Evidence Collection   Must collect all possible carriers of    evidence       Head and pubic hairs           For compar...
Special Considerations for Arson   Accelerants       Volatile, evaporate        easily       Collect ash and        deb...
Standard/Reference Samples   To show provenance        Substrate Controls    you need known                Samples of m...
Chain of Custody   Key point of attack for the defense   Every person who handled or    examined the evidence must be   ...
Safety Considerations   AIDS and other infectious materials       Double gloves, shoe covers, Tyvek suit       Blood mu...
Legal Considerations   4th Amendment Rights       Right against unreasonable search and        seizure           Probab...
Searching without a warrant   Emergency circumstances   Prevent loss or destruction of    evidence   Search of person a...
Key Court Decisions   Mincey v. Arizona       Undercover cop killed trying to buy drugs       Police search scene for f...
Key Court Decisions   Michigan v. Tyler       Arson at a place of business       Police search scene looking for arson ...
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Processing the crime scene

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Processing the crime scene

  1. 1. Processing the Crime Scene Securing Physical Evidence http://i.cnn.net/cnn/SPECIALS/2000/columbine.cd/Photos/ENTRYWAY.01.JPG
  2. 2. What is Physical Evidence? Any and all objects that can:  establish that a crime has been committed  link a crime and a victim  link a crime and the perpetrator Selectivity is the key  You can’t collect everything!
  3. 3. Priorities at the Crime Scene Obtain medical aid for those in need Arrest the perpetrator Secure the crime scene  Exclude unauthorized personnel  Remember Locard’s Exchange Principle!  Determine crime scene boundaries  Locate path of entry and exit
  4. 4. Photography Scene must be unaltered!  If objects are removed, positions changed, or items added photos may be inadmissable  If items were moved (eg. Securing a firearm) note it in the report, do not put it back! Physical evidence must be photographed to show:  Position and location relative to the scene  Close-ups to show detail  Scale to show size
  5. 5. Sketches Rough sketch records  Dimensions of crime scene and surroundings  Location of each piece of physical evidence  Distances from two points Finished sketch  Represents crime scene to the jury
  6. 6. Systematic Search Patterns Spiral search Grid method Strip of line search Quadrant or zone search http://www.tpub.com/maa/12740_files/image598.jpg
  7. 7. Evidence Collection Must collect all possible carriers of evidence  Clothing  Package each item separately  Cross- contamination  Sweepings  Collect and package each area separately  Fingernail scrapings
  8. 8. Evidence Collection Must collect all possible carriers of evidence  Head and pubic hairs  For comparison purposes  Blood or cheek swab for DNA  Vaginal, anal and oral swabs  For sex crimes  Recovered bullets from the body  Hand swabs for gunshot residue
  9. 9. Special Considerations for Arson Accelerants  Volatile, evaporate easily  Collect ash and debris for traces  Store in airtight paint cans with vapor concentrators
  10. 10. Standard/Reference Samples To show provenance  Substrate Controls you need known  Samples of materials reference samples to near where physical compare to evidence was  Hair deposited  Fiber  Want to show tests for physical evidence  Glass don’t produce false  DNA positives  Blood  Untouched wallboard in arson  Background fabric for blood test
  11. 11. Chain of Custody Key point of attack for the defense Every person who handled or examined the evidence must be accounted for  Must be a written record of each hand- off  Each time container is opened a fresh seal must be made and initialed
  12. 12. Safety Considerations AIDS and other infectious materials  Double gloves, shoe covers, Tyvek suit  Blood must be dried  Biohazard bags Air-borne particulates and dust  Particle mask, respirator, goggles, face shield Sharps and blood contamination No eating, drinking, smoking, putting on make-up
  13. 13. Legal Considerations 4th Amendment Rights  Right against unreasonable search and seizure  Probable cause  Description of place to be searched  Description of persons or things to be seized
  14. 14. Searching without a warrant Emergency circumstances Prevent loss or destruction of evidence Search of person and property during an arrest Search made with consent
  15. 15. Key Court Decisions Mincey v. Arizona  Undercover cop killed trying to buy drugs  Police search scene for four days without obtaining a warrant  Supreme Court throws out the evidence found  “No exigent circumstances”
  16. 16. Key Court Decisions Michigan v. Tyler  Arson at a place of business  Police search scene looking for arson but leave scene unattended for several hours  Return several times over next 4 weeks to collect evidence without warrant  Initial warrantless search is OK after fire  Later searches thrown out
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