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Introduction to Crime Scene Investigation ILEETA

Introduction to Crime Scene Investigation ILEETA. Thanks to Edward E. Hueske University of North Texas Denton, Texas. Duties of First Officer to Scene. Make scene safe for entry Provide medical attention to injured Secure scene Preserve physical evidence Detain witnesses

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Introduction to Crime Scene Investigation ILEETA

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  1. Introduction to Crime SceneInvestigationILEETA Thanks to Edward E. Hueske University of North Texas Denton, Texas

  2. Duties of First Officer to Scene • Make scene safe for entry • Provide medical attention to injured • Secure scene • Preserve physical evidence • Detain witnesses • Request assistance as needed

  3. Crime Scene Investigation • Team approach will be used • One person must be in charge • Equipment and supplies must be present • Duties must be designated • Search method(s) must be established • Security of scene must be confirmed • Priorities in processing must be established

  4. The Team Approach • Team leader is established prior to arrival Thanks a lot This one’s yours, I had the last one

  5. Duties of Team Leader • Meet with first officer for briefing • Confirm security • Determine legality of search (search warrant) • Call for additional personnel/equipment • Survey scene with first officer • Note fragile evidence/establish priorities • Make notes as to initial observations • Work out action plan with team

  6. Appropriate Crime Scene Attire • Gloves • Shoe covers • Disposable suit • Head gear • Eye protection • Breathing apparatus

  7. Appropriate Crime Scene Behavior • Do not smoke, eat, drink, etc. within the scene • Do not bring equipment into scene and set down within the scene if at all possible • Do not place foreign items down in scene

  8. Documenting the Scene • Photography • Video Taping • Sketching • Diagramming • Note Taking • Report Writing

  9. Scene Searches • Spiral search • Line (strip) search • Grid search • Quadrant (sector)

  10. Vehicle Searches • Photograph as found • Begin with exterior exam/print search • Divide interior into areas • Undercarriage exam (hit & runs) • Inventory and document items as removed • Have items tested as appropriate

  11. Autopsy Evidence • Hair standards • Blood samples – purple-topped tubes • Prints • Fingernail scrapings • GSR test • Sexual assault kit • Recovered bullets, etc.

  12. Collection and Packaging of Evidence • Do not use plastic to package biological evidence • Most evidence is best packaged by placing into a clean sheet of paper, folding, taping and placing in an envelope and sealing • Package evidence separately • Use sharps containers when needed • Obtain required control samples • Maintain a chain of custody record • Use biohazard bag to dispose of contaminated items (gloves, shoe covers, etc.)

  13. Crime Scene Photography • First frame is data card (ea. Roll) • General to specific • Outside to inside • Special documentation (street sign, house number, VIN tag, etc.) Remember: You can’t take too many pictures, but you can take too few!

  14. Crime Scene Photography Scaled Photography • Camera back is in same plane as subject • Fill frame with subject • Include a scale in 1 photo & 1 w/o scale • Use oblique lighting as required • Use a tripod and remote shutter release

  15. Crime Scene Photography Specialized Techniques • Painting with light • Fill-flash • Spray paint “shadowing” • Luminol

  16. Crime Scene Photography Painting with Light • Use for night photography of large outdoor scenes • Use for time exposures of impressions in dust with flashlight

  17. Crime Scene Photography • Use to show background with luminal • Initial exposure of luminal reaction with lens wide open • Manually fire strobe after exposure (use shield on strobe) Fill-Flash

  18. Crime Scene Photography Spray Paint “Shadowing” • Use with available light • Use for impressions in snow • Use for impressions in sand or other soil • Flat black or flat white works best • Spray at an oblique angle

  19. Types of Physical Evidence • Blood, Semen and Saliva • Documents • Drugs • Explosives • Fibers • Fingerprints • Firearms evidence

  20. Types of Physical Evidence • Glass • Hair • Two-dimensional and three-dimensional Impressions • Body fluids and organs • Paint • Petroleum products • Plastic bags (garbage)

  21. Types of Physical Evidence • Polymers & Plastics • Gunpowder Residues • Serial Numbers • Soil and Minerals • Tool Marks • Vehicle Lamp Bulbs • Wood & Vegetative Matter

  22. The Goal of Physical Evidence • Positive Identification • Association • Circumstantial

  23. Comparative Analysis • Known to Unknown or “Q” to “K” • Physical comparison (physical properties/jig-saw puzzle fit) • Chemical comparison • Class characteristics • Individual characteristics

  24. Range of Conclusions • Identification (common origin) • Same source or a similar source (either/or) • Member of same class (cannot be excluded) • Exclusion (different origin)

  25. Ignorance is Bliss • What is a class characteristic? • What is and individual characteristic? Knowledge is the key

  26. Evidence and Probability • Most of the time a mathematical expression is inappropriate (Highly probable vs. highly improbable) • Some situations do lend themselves to a mathematical expression of probability (DNA is a prime example)

  27. Probability and Statistics • Coin toss – 1 in 2 probability • Roll of a die – 1 in 6 probability • Roll of a pair of dice to yield “snake eyes” – 1/6 x 1/6 = 1/36 (1 in 36 probability) • There are 4 aces in a deck of 52 cards, what is the probability of drawing an ace at random? • What is the probability of drawing a king of any suit? • What is the probability of drawing an ace and a king with 2 draws from a full deck?

  28. Probability and Statistics • DNA analysis is based on the presence of certain fragments within the DNA molecule • For each fragment there is a certain frequency (probability of occurrence) within a particular ethnic group of a population • If 7 different fragments are identified as being present, how is the probability of that occurring in someone else calculated?

  29. Probability and Statistics • A vehicle with 4 different brands of tires leaves all 4 different tread patterns at a crime scene. A suspect is arrested with a car with 4 different tires, each similar to one of the crime scene impressions. • Is it possible to calculate the probability of finding the same situation on another car? • What considerations are involved?

  30. Negative Evidence • “Absence of Evidence is not evidence of absence” • Nevertheless, what is not present can provide useful information as to how a crime may have been committed • Ex: No shoe impressions on driver side of vehicle but shoe impressions leaving the passenger side • Faulty reasoning: no blood in trunk, therefore victim was not transported in trunk.

  31. Crime Scene Reconstruction • Who? • What? • When? • Where? • How? • Why?

  32. Crime Scene Reconstruction • On-scene • Off-scene • Re-enactment: • Live actors • Mannequins

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