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The Crime Scene

The Crime Scene

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The Crime Scene

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  1. Honors Forensic Science The Crime Scene

  2. I. Processing the Crime Scene • Crime Labs “run” on physical evidence • Physical Evidence = any and all objects that can establish that a crime has been committed or can provide a link between a crime and its victim or a crime and its perpetrator

  3. To be effective, evidence must be: • Recognized • Collected and processed properly • Collector must be selective using knowledge of crime lab techniques, capabilities and limitations

  4. Crime labs do not solve crimes • Many jurisdictions have specialized teams to conduct crime-scene searches • Not all crime scenes require retrieval of physical evidence

  5. II. Secure and Isolate Crime Scene • First officer(s) on scene should: • Provide medical assistance, if needed, to victims • Arrest perpetrator if present • Preserve and protect area as much as possible

  6. II. Cont’ d • Exclude all unauthorized personnel from scene • Isolate area using ropes, tape, barricades, guards, etc.

  7. Lead Investigator should: • Determine boundaries • Determine perp’s path of entry and exit • Document obvious items • Conduct initial walk-through • Develop examination strategy

  8. Record the Scene • Must document the crime scene in original state • Information used in investigation and in court • Monetary limitations may determine method used to document the scene

  9. Photography • Must be in unaltered condition • Crime scene photographed completely • Items of physical evidence photographed to show position and location; close-ups to show detail • If size is important, include a measurement scale in photo for reference

  10. Videography • Can be used to augment photography • Can narrate events on videotape • Does not replace photography

  11. Sketches • Rough Sketch • Containing an accurate depiction of the dimensions of the scene and showing the location of all objects having a bearing on the case

  12. Rough sketch should include; • Recovered items of physical evidence • Distance measurements of items (use 2 fixed points) • Legend • Compass heading designating north

  13. Finished Sketch • A precise rendering of the crime scene, usually drawn to scale • Often prepared with aid of templates and drafting tools • Reflect same information as rough draft • CAD programs often used

  14. Notes • Must be a constant activity • Should include detailed written description of scene • Detailed description of evidence: location of items, time item discovered, by whom, how and by whom it was packaged, etc.

  15. Notes often only written record of details • Tape-recording can be advantageous, but still should be transcribed into a written document

  16. Conduct Systematic Search • Thorough and systematic, even if seems unnecessary at the time • How crime scene is searched depends on type of crime, local and size of scene, # of collectors, etc.

  17. Collect massive objects to microscopic traces • Important to collect possible carriers of trace evidence as well as obvious items • Portable vacuum cleaners helpful • Medical examiner may also provide evidence

  18. Medical examiner may collect and forward: • Victim’s clothing • Fingernail scrapings • Head and pubic hairs • Blood (for DNA typing) • Vaginal, anal, and oral swabs • Recovered bullets from body • Hand swabs from shooting victims

  19. Collect and Package Physical Evidence • Prevent change • Change can arise from contamination, breakage, evaporation, accidental scratching or bending, or loss through improper or careless packaging • Maintain evidence in original condition if possible

  20. Each different item or similar items collected at different locations must be placed in separate containers. Packaging evidence separately prevents damage through contact and prevent contamination

  21. Maintain Chain of Custody • Chain of custody – list of all persons who came into possession of an item of evidence • Must be established whenever evidence is presented in court • Adhere to standard procedures • Keep to a minimum

  22. Obtain Controls • Examination of evidence often requires comparison with known standard or control • Control = physical evidence whose origin is known, such as blood or hair from a suspect, that can be compared to crime scene evidence

  23. Quality and quantity of controls may help determine evidential value of crime-scene evidence • Controls must be treated with equal care as actual evidence

  24. Submit Evidence to Lab • Usually submitted personally or by mail shipment • Must be accompanied by evidence submission forms • List of tests to be performed on each item • List of items submitted

  25. Crime Scene Safety • International Association for Identification Safety Committee • Gloves • Particle masks/respirator, goggles, face shield • Be alert to sharp objects • Use biohazard bags • Note taking done with uncontaminated gloves • No eating, drinking, smoking, etc. at crime scenes

  26. Legal Considerations • Fourth Amendment – Prohibits unreasonable search and seizure • Mincey v. Arizona • Michigan v. Tyler • When time and circumstances permit, obtain a search warrant before investigating and retrieving physical evidence at crime scene