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Forensics: Chapter 2 The Crime Scene

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  1. Forensics: Chapter 2The Crime Scene

  2. Objectives: • Explain and demonstrate techniques for securing, evaluating, recording, and preserving a crime scene and physical evidence. • Describe relevant court cases relating to the 4th Amendment and searches.

  3. Forensic Science Begins At The Crime Scene! • Two Types Of Crime Scenes: • Primary • “where the crime was actually committed” • Secondary • “related to the crime but is not where the actual crime took place”

  4. 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.

  5. Physical Evidence: • May do any or all of the following: • Link a suspect to a crime. • Corroborate or refute an alibi or statement. • Identify a perpetrator or victim. • Exonerate the innocent • Induce a confession. • Direct further investigation

  6. Evidence Can Be: • Direct • Establishes a fact • Ex: eyewitness statements & confessions • Circumstantial • Requires that a judge and/or jury make an indirect judgment. • Most common type of evidence identified. • Often much more reliable. • Usually more objective.

  7. Arriving At The Crime Scene! • The officer who responds first must: • Arrest the perpetrator(s)….if present. • Assist any victims present…(first aid, etc) • Begin preserving the crime scene • Detain suspects and witnesses (avoid collusion!) • Establish a security log (sign in/out sheet for any and all visitors).

  8. After Securing The Crime Scene: • A lead investigator will start the process of evaluating the area. • Establish the size and boundaries of the crime scene. • Establish the perpetrator’s path of entry and exit. • Documentation of obvious items of evidence (written, direction, photograph). • Initial walk-through of scene to gain an overview and develop a strategy for systematic examination and documentation of entire crime scene.

  9. Methods of Crime Scene Recording: • Photography: • May or may not be utilized (personnel or monetary limitations). • Must be taken as soon as possible to preserve the scene in the unaltered state. • Must be taken prior to removing any evidence, including the body.

  10. Methods of Crime Scene Recording: • Photography (cont) • Must include entire room as well as adjacent rooms (if crime was committed indoors). • Multiple angles and points of view. • Include a point of reference for size (ruler or other common object.

  11. Methods of Crime Scene Recording: • Sketches: • Show relationship of each item of evidence to other items or to the body. • Each piece of evidence is mapped based on its distance from 2 fixed points. • Must include a compass heading designating North.

  12. Methods of Crime Scene Recording: • Sketches (cont): • Includes numbers or letters (designating evidence) as well as a legend. • Initially rough, but can be redrawn later for clarity and aesthetics (usually to scale). • Computer programs (CAD) are available to help generate clear drawings.

  13. Methods of Crime Scene Recording: • Notes: • Constant activity throughout the processing of a crime scene. • Detailed (written description of the scene as well as items found) • Must identify: • Time the item of evidence was discovered. • Who discovered the evidence. • How and by whom the item of evidence was packaged and marked. • Disposition of the item after it was collected.

  14. Methods of Crime Scene Recording: • Videotape: • Becoming more popular due to decrease in cost of equipment. • More convenient (combines note-taking with photography). • Written documentation is still required.

  15. Locating Evidence: • Locating evidence can be straight forward or more difficult (the probable location of the evidence is not always associated with the crime scene and/or the police are not always invited to search. • The success in the recognition and collection of physical evidence is directly related to the skill of the personnel processing the scene.

  16. The 4th Amendment: • Protects citizens against unreasonable searches and seizures! • The removal of any evidence from a person or from the scene of a crime must be done in accordance with the privileges of the 4th Amendment to the Constitution. Therefore, police must have a warrant prior to searching for evidence.

  17. Warrants: • Must include (and be specific about): • Time • Place(s) to be searched • Items for which investigators are looking. • Be obtained on the basis of probable cause (solid legal reason).

  18. Warrantless Searches: • The Supreme Court has allowed warrantless searches to stand in the following situations: • Emergency situations. • Impending loss of evidence. • Lawful arrest. • Consented search.

  19. Search Patterns: • To find evidence that is not obvious, investigators must take an orderly approach in searching a crime scene. • This depends on the size and layout of the area in question.

  20. Search Pattern Types: • Grid • Strip or Line • Quadrant or Zone (requires more than one investigator) • Spiral

  21. Hit and Run Physical Evidence: • Hit and run evidence should include any evidence of cross-transfer such as: • Blood • Glass fragments • Fiber(s) • Tissue(s) • Fabric impressions • Paint

  22. Autopsy Room Evidence: • The search for physical evidence must extend beyond the crime scene. • Types of evidence retrieved by the medical examiner can include: • Clothing • Fingernail scrapings • Head and pubic hair • Oral, vaginal, and anal swabs • Bullets • Hand swabs for GSR

  23. Gathering Evidence: • The successful outcome of a criminal investigation is directly related to the manner in which the evidence is collected and preserved! • Start with evidence that is fragile or likely to be damaged, lost, or contaminated (blood, shoe, tire, or finger prints, fibers) • The manner of collecting and preserving physical evidence is determined by the nature of the evidence.

  24. Gathering Evidence (examples): • Fingerprints – photographed, lifted, and transferred to a material that can be carried by the investigator. • Tool marks, Shoe prints, Tire impressions –photographed, lifted or cast • Fibers, Hair – searched with various light sources, gathered with tweezers • Carpet, Furniture – vacuumed using fresh vacuum bag for each area.

  25. Packaging Evidence: • All items of evidence must be carefully packaged and marked up their retrieval at the crime scene. • A minimum record of marking should include: • Collector’s initials • Location of the evidence • Date of collection

  26. Packaging Evidence (cont): • Each different item or similar items collected at different locations must be placed in separate containers (this prevents cross contamination). • Most dry evidence is placed in a “druggist fold”. • Wet evidence is placed in “non-airtight” containers or allowed to air dry completely before packaging.

  27. Other Packaging Options: • Depends on the type of evidence (see pgs 544-557) • Manila Envelopes • Plastic pill bottles • Canisters/Dry paint cans • Paper bags • Plastic bags

  28. Chain of Custody: • To prevent evidence from being declared inadmissible in court, a continuous record showing that evidence has been kept safe and secure must be made. • This is called “chain of custody” • “Chain of custody” is the responsibility of everyone involved in the collection, identification, packaging and transporting of physical evidence.

  29. Examining Evidence • Requires comparison with a known standard or reference sample (control) or may need to be accompanied by a substrate sample. • Control sample – sample taken from a known source. • Substrate sample – uncontaminated surface material close to an area where physical evidence has been deposited. • Buccal swab – swab of inner portion of cheek.

  30. Submitting Evidence: • Evidence is usually submitted to a lab either by personal delivery or by mail shipment. • Mode of delivery depends on • Distance the submitting agency must travel • Urgency of the case • Most labs require that an evidence submission form accompany all evidence submitted (see pg 48).

  31. Crime Scene Safety: • Crime scenes may pose potential health hazards. • The increasing spread of AIDS and hepatitis B are major personal concerns for investigators at crime scenes. • Both diseases are normally transmitted by: • Exchange of body fluids • Intravenous drug needles/syringes • Transfusion of infected blood products.

  32. 4th Amendment Court Cases: • Mincey v. Arizona • Michigan v. Tyler