Forensic Science: Topic 2 crime scene


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Forensic Science: Topic 2 crime scene

  1. 1. The Crime Scene
  2. 2. Info from Scene <ul><li>Linkage of persons, places and things </li></ul><ul><ul><li>Locard Exchange Principle : when two objects come into contact with one another, an exchange of matter takes place. </li></ul></ul><ul><ul><li>Physical evidence can link suspect, victim, crime scene, and objects to one another </li></ul></ul>
  3. 3. Info from Scene Victim Object Suspect Crime Scene
  4. 4. Info from Scene All found at scene
  5. 5. Info from Scene Bullet in Keenan
  6. 6. Info from Scene Fingerprints on gun
  7. 7. Info from Scene Kel’s Hair on Keenan
  8. 8. Info from Scene Kel’s suspenders’ button In dumpster
  9. 9. Processing The Crime Scene <ul><li>Forensic Science begins at the crime scene </li></ul><ul><li>- Physical Evidence: Any object (natural or manufactured) that can establish that a crime has been committed or can provide a link between a crime and its victim or between a crime and its perpetrator. </li></ul>
  10. 10. Fundamental Practices at a Crime Scene <ul><li>Secure and Isolate Crime Scene </li></ul><ul><li>Record Crime Scene </li></ul><ul><li>Photograph Crime Scene </li></ul><ul><li>Sketch Crime Scene </li></ul><ul><li>Maintain excellent Notes </li></ul><ul><li>Conduct Systematic Search for Evidence </li></ul><ul><li>Collect and Package Physical Evidence </li></ul><ul><li>Maintain Chain of Custody </li></ul><ul><li>Obtain Standard/Reference Samples </li></ul><ul><li>Submit Evidence to Library </li></ul><ul><li>Maintain Safety at Crime Scene </li></ul>
  11. 11. Secure and Isolate Crime Scene <ul><li>Responsibility of the first officer arriving on the scene. </li></ul><ul><li>Medical assistance must be given to anyone in need </li></ul><ul><li>Scene must be preserved and protected because every person entering scene is a potential destroyer of evidence (intentionally or accidentally) </li></ul><ul><ul><li>No unauthorized personnel (including spectators, unauthorized police officers and media) on scene </li></ul></ul><ul><ul><li>Ropes, tape, barricades used to secure scene </li></ul></ul><ul><ul><li>Record maintained of all people entering and leaving crime scene </li></ul></ul>
  12. 12. Record Crime Scene <ul><li>Once the crime scene is secure, the lead investigator evaluates the area. There is a very limited amount of time to process scene before it gets disrupted by various personnel </li></ul><ul><ul><li>Boundaries of crime scene determined </li></ul></ul><ul><ul><li>Initial walk-through conducted </li></ul></ul><ul><ul><li>Strategy developed to process scene </li></ul></ul><ul><ul><li>Photograph and/or sketch scene </li></ul></ul><ul><ul><li>Take detailed notes </li></ul></ul>
  13. 13. Photograph Crime Scene <ul><li>Photographs must be taken without altering the scene or moving objects (unless there are injured people that need medical attention). </li></ul><ul><li>If anything gets moved, photos may not be admissible in court as evidence. </li></ul><ul><li>Detailed notes should be taken to override this issue. </li></ul>
  14. 14. Photography cont’d. <ul><li>Crime scene must be photographed thoroughly (from various angles) </li></ul><ul><li>All adjacent areas as well </li></ul><ul><li>All points of entry and exit </li></ul><ul><li>If scene includes body, pictures of the position and location relative to entire scene must be taken </li></ul><ul><li>Close-ups of injuries, weapons </li></ul><ul><li>Once body is removed, the surface under body must be photographed </li></ul><ul><li>Each piece of physical evidence must be photographed in its original location next to a ruler or other measuring device AND a number I.D. card </li></ul><ul><li>Video recorders are also being used these days, but have not replaced still photographs </li></ul>
  15. 16. Sketch Crime Scene <ul><li>Once photographs are taken, the crime-scene investigator will sketch the scene (a rough sketch, since there is no time to make a polished one) </li></ul><ul><li>A rough sketch employs geometric shapes and letters and numbers. </li></ul><ul><li>A finished sketch is created with mush more care and detail. Computer aided drafting (CAD) can be employed to do this. </li></ul>
  16. 17. Accurate measurements to two fixed points must be recorded so that a scaled final sketch can be prepared for court presentation. What are good examples of fixed points?
  17. 18. Where are the fixed points in this room?
  18. 19. Rough Sketch Final Sketch
  19. 20. The Finished Sketch <ul><li>Is usually prepared for courtroom presentation. </li></ul><ul><li>Must be to scale i.e. ¼ in. = 1 ft. </li></ul><ul><li>Units used must be consistent </li></ul><ul><li>i.e. make all measurements in metric or in feet/inches do not combine. </li></ul>
  20. 21. Bird's eye view 2 dimentional representation
  21. 22. Crime Scene Documentation <ul><li>Sketching the Crime Scene </li></ul><ul><ul><li>Goal is to record exact position of all evidence to aid in reconstruction. </li></ul></ul><ul><ul><li>Rough sketches can be refined into final sketches </li></ul></ul><ul><ul><li>Three techniques of measurement are used: </li></ul></ul>X Y X Y X Y Triangulation Baseline Polar Coordinates e e e 30 °
  22. 23. Crime Scene Sketch Date: August 14, 2001 Criminalist: Ann Wilson Time: 11:35 Location: 4358 Rockledge Dr St. Louis, Mo. <ul><ul><li>A. Couch/sofa </li></ul></ul><ul><ul><li>B. Female body </li></ul></ul><ul><ul><li>C. Knife </li></ul></ul><ul><ul><li>D. Over turned Lamp </li></ul></ul><ul><ul><li>E. Chairs </li></ul></ul><ul><ul><li>F. Table </li></ul></ul><ul><ul><li>G. Fireplace </li></ul></ul>c D E E E E E A G F
  23. 24. Rough Sketch
  24. 25. Finished Sketch – Hand Drawn
  25. 26. Finished-sketch diagram of a crime scene. Courtesy Sirchie Finger Print Laboratories, Inc., Youngsville, N.C., .
  26. 27. Maintain Excellent Notes <ul><li>Must be a constant activity </li></ul><ul><li>Must include a written description of scene and location of all objects of physical evidence </li></ul><ul><li>Tape-recorded notes can be more advantageous – faster. But at some point in time the tapes must be transcribed into written/typed notes. </li></ul>
  27. 28. Conduct Systematic Search for Evidence <ul><li>Physical evidence may be large or microscopic, therefore searches have to be conducted with extreme care and have to be thorough. </li></ul><ul><li>Hap-hazard searches will lead to important clues being missed or lost. </li></ul><ul><li>Systematic searches, using specific patterns are used. </li></ul><ul><li>Critical areas of the scene may be vacuumed with portable vacuum cleaners equipped with special filters </li></ul><ul><li>The search for physical evidence must extend beyond the crime scene to the autopsy room of the victim – the medical examiner will contribute to the evidence list with results of toxicology and pathology examinations of various body parts, organs, tissues, etc. </li></ul>
  28. 29. Spiral Search
  29. 30. Grid and Zone Also called the Quadrant Method
  30. 31. Parallel
  31. 33. Vacuum sweeper attachments
  32. 34. The following list of physical evidence is collected to be sent to the forensic laboratory: <ul><li>Victim’s clothing </li></ul><ul><li>Fingernail scrapings </li></ul><ul><li>Head and pubic hairs </li></ul><ul><li>Blood (For DNA typing) </li></ul><ul><li>Vaginal, anal, oral swabs (sex-crimes) </li></ul><ul><li>Bullets recovered from body </li></ul><ul><li>Hand swabs from shooting victims (GSR tests) </li></ul>
  33. 37. Collect and Package Physical Evidence <ul><li>Physical evidence must be collected and packaged correctly so it does not change from the time it was collected to the time it is processed by the crime lab. Changes such as evaporation, contamination, breakage, etc. </li></ul><ul><li>Each different piece of physical evidence must be packaged separately. </li></ul><ul><li>Evidence must be handled with forceps (gloved hands only) or similar tools </li></ul>
  34. 38. Collect and Package Physical Evidence <ul><li>Plastic pill bottles, manila envelopes, glass bottles: for storing hair, fibers, glass and various small or “trace” evidence. </li></ul><ul><li>Paper with “druggist fold”: an alternative way to store trace evidence. </li></ul>
  35. 39. Blood-stained materials must be stored in paper bags or manila envelopes <ul><li>Blood-soaked clothing must NOT be stored in air-tight containers because the trapped moisture may cause the growth of mildew and mold and destroy the blood. </li></ul><ul><li>All clothing in fact, must be air-dried and individually stored in paper bags. </li></ul><ul><li>Charred clothing or debris on the contrary, MUST be stored in air-tight containers so that evaporation of volatile petroleum residues does not occur. </li></ul>
  36. 43. Maintain Chain of Custody <ul><li>A list must be maintained of all persons who came into possession of a particular item of evidence. </li></ul><ul><li>Failure to do this may will lead to serious questions regarding the authenticity and integrity of the evidence and it may not be admissible in court. </li></ul><ul><li>Each time an evidence container is opened and closed, it must be sealed with a label with the examiner’s name, date and location of the item. </li></ul><ul><li>If the evidence is moved to another location/lab, the date of this transfer must also appear on the label. </li></ul><ul><li>In addition, a complete record of all persons in touch with the evidence is maintained and these persons may be summoned to court to testify during court proceedings. </li></ul>
  37. 45. Obtain Standard/Reference Samples <ul><li>All evidence must be compared to with a known (standard/reference) sample </li></ul><ul><li>For example, blood-stained evidence must be accompanied by blood or buccal samples from both the victim as well as the suspect(s) </li></ul><ul><li>Same is true with hair, fibers, soil, etc. </li></ul>
  38. 46. Submit Evidence to Library <ul><li>Can be delivered to lab by personal delivery or mail delivery but certain materials cannot be mailed – explosive, certain chemicals, live ammunition, etc. </li></ul><ul><li>Receiving lab must get a case history or any such report along with the evidence. </li></ul><ul><li>There should be a clear request of type of examination for each piece of evidence – however, an analyst may perform other tests on the pieces of evidence if necessary (in addition to the tests requested) </li></ul><ul><li>An evidence submission form must be completed with a list of all evidence items being submitted for tests. </li></ul>
  39. 47. Crime-scene Safety <ul><li>All CSI have to be extremely careful due to the increasing spread of HIV, Hepatitis B&C, and other diseases carried in bodily fluids. </li></ul><ul><li>Inoculations against Hepatitis B are made available to all law enforcement officials according to OSHA (Occupational Safety and Health Administration) </li></ul>
  40. 48. CSI Safety Guidelines: <ul><li>Double layer of latex gloves </li></ul><ul><li>Protective Tyvek ® shoe covers </li></ul><ul><li>Tyvek ® or Kleengard ® coveralls or suits (liquid repellant) </li></ul><ul><li>Particle mask/respirator, goggles/face shield to prevent exposure to dust, mist, body fluids, etc. </li></ul><ul><li>Be aware of sharp objects like broken glass, knives, needles, etc. </li></ul><ul><li>Use biohazard labels when collecting materials hazardous to health. </li></ul><ul><li>All gloves, masks, suits must be disposed of in red biohazard bags, taped shut and sent to a proper facility for incineration. </li></ul><ul><li>Note-taking should be done with fresh, uncontaminated gloves to prevent contamination of pens, pencils and notepads. </li></ul><ul><li>Torn or soiled protective gear must be removed immediately and replaced with a fresh one, AFTER the individual disinfects the contaminated body area with 10% bleach solution, antimicrobial wipes, etc. </li></ul><ul><li>Absolutely no eating, drinking, smoking in the crime scene or laboratory. </li></ul><ul><li>All non-disposable items such as cloth lab coats, etc. must be placed in yellow bags labeled “Infectious linen” and sent to a proper facility for laundering and disinfection. </li></ul>
  41. 49. CSI Clean-up crew
  42. 50. Legal Considerations at a Crime Scene <ul><li>The removal of any person or evidence from a crime scene must be done in conformity with Forth Amendment privileges: </li></ul><ul><ul><li>The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized. </li></ul></ul>
  43. 51. Warrant or no warrant <ul><ul><li>Therefore, search warrants are required. A warrantless search can only be conducted under the following circumstances: </li></ul></ul><ul><ul><li>Existence of an emergency </li></ul></ul><ul><ul><li>To prevent immediate loss or destruction of evidence </li></ul></ul><ul><ul><li>Search of a person or property of the person during his arrest </li></ul></ul><ul><ul><li>Search an seizure with the consent of the persons involved </li></ul></ul>
  44. 52. Let the evidence speak for itself. Physical Evidence Chapter 3
  45. 53. Remember: Locard’s Exchange Principle &quot;Every Contact Leaves a Trace&quot; The Locard’s Exchange Principle states that &quot;with contact between two items, there will be an exchange.&quot; For example, burglars will leave traces of their presence behind and will also take traces with them. They may leave hairs from their body or fibers from their clothing behind and they may take carpet fibers away with them. The value of trace (or contact) forensic evidence was first recognized by Edmund Locard in 1910. He was the director of the very first crime laboratory in existence, located in Lyon, France.
  46. 54. Physical Evidence <ul><li>Blood, Semen, Saliva </li></ul><ul><li>Documents </li></ul><ul><li>Drugs </li></ul><ul><li>Explosives </li></ul><ul><li>Fibers </li></ul><ul><li>Fingerprints </li></ul><ul><li>Firearms and Ammunition </li></ul><ul><li>Glass </li></ul><ul><li>Hair </li></ul><ul><li>Impressions </li></ul>
  47. 55. Physical Evidence <ul><li>Organs and Physiological Fluids </li></ul><ul><li>Paint </li></ul><ul><li>Serial Numbers </li></ul><ul><li>Tool Marks </li></ul><ul><li>Other </li></ul>
  48. 56. Physical Evidence <ul><li>Identification - Determination of physical or chemical identity of a substance with as near absolute certainty as the analytical method will permit. </li></ul><ul><ul><li>What is the material? How certain is the answer? What analytical method(s) will give the best answer (multiple methods)? </li></ul></ul><ul><li>Comparison - Compares standard and suspect samples to determine if they have a common origin. </li></ul><ul><ul><li>Can the source of the sample be identified? How certain is the correlation? How many “data points” are necessary to be “certain beyond a reasonable doubt” of the answer (probability)? </li></ul></ul>
  49. 57. Identification - Determination of the physical and chemical identity of a substance with as near absolute certainty as existing analytical techniques will permit. <ul><li>Examples: drug analysis, species determination & explosive residue that contain dynamite. </li></ul><ul><li>Example: Gas Chromatography / Mass Spectrometry (GC/MS). Accurate identification of a compound. </li></ul>
  50. 58. Comparisons <ul><li>Analysis of a suspect specimen WRT a standard/reference (exemplar) specimen to determine whether or not they have a common origin . </li></ul>Common Origin?
  51. 59. Physical Evidence <ul><li>Class (Group) Characteristics - Properties of evidence that can only be associated with a general group and not with a common source. e.g., blood type, paint or dye lot, etc. </li></ul><ul><li>Individual Characteristics - Properties of evidence that can connect a sample and standard to a common source (with high probability). e.g., fingerprints, unusual wear patterns, tool marks, etc . </li></ul>
  52. 60. Physical Evidence <ul><li>Class (Group) Characteristics - Properties of evidence that can only be associated with a general group and not with a common source. e.g., blood type, paint or dye lot, etc. </li></ul>Blood Types World : Type A - 42% Type B - 8% Type O - 47% Type AB - 3% US : Type A - 39% Type B - 13% Type O - 43% Type AB - 5% “ Bodies of Evidence” Brian Innes
  53. 61. Class Characteristics <ul><li>Properties of evidence that can only be associated with a group and never with a single source. </li></ul><ul><li>Can be used to exculpate a suspect. </li></ul><ul><li>Examples: single-layer paint chip, blood, nylon fiber from a sweater </li></ul>Where is Waldo?
  54. 62. Physical Evidence <ul><li>Class (Group) Characteristics - Properties of evidence that can only be associated with a general group and not with a common source. e.g., blood type, paint or dye lot, etc. </li></ul><ul><li>Individual Characteristics - Properties of evidence that can connect a sample and standard to a common source (with high probability). e.g., fingerprints, unusual wear patterns, tool marks, etc. </li></ul>Example: from “My Cousin Vinny” (20th Century Fox)
  55. 63. Physical Evidence <ul><li>Class (Group) Characteristics - Properties of evidence that can only be associated with a general group and not with a common source. e.g., blood type, paint or dye lot, etc. </li></ul><ul><li>Example: from “My Cousin Vinny” (20th Century Fox) </li></ul><ul><ul><li>2 people charged with murder during a robbery at a convenience store (“Sack-O-Suds”). </li></ul></ul><ul><ul><li>Escaped in an older car and skidded tires while leaving. </li></ul></ul><ul><ul><li>Witnesses confused but say they saw the two defendants. </li></ul></ul><ul><ul><li>Expert from FBI called to match tire skids with defendants car. </li></ul></ul>
  56. 64. Examples :  Vomit and urine can be used to test for alcohol, drugs, and poisons.  Cigarette butts may contain dried saliva.  Semen containing sperm is valuable for DNA analysis.  Blood can provide DNA evidence and blood spatter can provide clues about the crime. Body Fluids • Blood, semen, saliva, sweat, and urine can be analyzed to give investigators information about the crime as well as its victim or the suspect. • Chemicals and ultra violet light can be used at a crime scene to find body fluid evidence. Areas with potential evidence are swabbed, bagged and collected in vials, which are air tight and have a low risk of cross contamination. Evidence Examples
  57. 65. Questioned Documents • Examiners will analyze a ransom note or other document to find clues to link it to a crime scene or a specific suspect. They will analyze the type of paper used, printing method or handwriting style, and type of ink. • Other unique features, such as watermarks on stationary or indentations made as someone wrote on a page in a notebook, may provide useful clues.
  58. 66. <ul><li>Explosives </li></ul><ul><li>• Explosive substances can be examined to determine its chemical composition to identify the type of explosive used and its origin. </li></ul><ul><li>• Traces of explosives found on a suspect’s clothing, skin, hair, or other objects may be matched to explosives from the crime scene. </li></ul><ul><li>Materials used to make an explosive device will be compared to evidence found in the suspect’s possession to confirm a match. </li></ul>
  59. 67. Hairs & Fibers • Hairs and fibers may be transferred from the suspect or the suspect’s clothes to the victims’ and vice versa. For example, a suspect may pick up carpet fibers on his shoes or leave hairs behind at a crime scene. •  Hairs can be examined to identify their origin, such as human or animal. Hairs with roots intact can be tested for DNA. • Fibers are used to make clothing, carpeting, furniture, beds, and blankets. They may be natural fibers from plants or animals or synthetic fibers that are man-made. Microscopic Image of Hairs & Fibers
  60. 68. Fingerprints <ul><li>•  There are 3 types of fingerprint patterns: arches, loops, and whorls. Investigators also identify unique ridge characteristics in a fingerprint that can be used to identify a suspect or victim. </li></ul><ul><li>•  AFIS (Automated Fingerprint Identification System) is a database used by investigators at local, state, and national levels to search for matches to fingerprints found at a crime scene . </li></ul>
  61. 69. Wounds/Organs and Physiological Fluids <ul><li>• Wounds can often be matched to weapons or tool marks on the weapon. Investigators may also be able to determine the weapon's size, shape, and length.  </li></ul><ul><li>•  Analysis of a wound may provides clues to a victim’s injuries, characteristics of the suspect (left-handed, right-handed, height, etc.), and positions of the victim and suspect at the time of the incident. </li></ul>
  62. 70. Dust & Dirt • Dust, dirt, or sand evidence can reveal where a person has traveled and may be picked up at a crime scene or left behind. • Investigators examine the samples for chemical composition, pollen, plant material, and other organic matter to find links to a specific crime scene. Microscopic Image of Sand
  63. 71. <ul><li>Ballistics </li></ul><ul><li>•  Characteristics of ammunition, firearms, and residue are examined to find matches between suspects and the evidence found at a crime scene. </li></ul><ul><li>• Chemical tests can reveal gunshot residue (GSR) on the hands, face, or clothing of a victim or suspect to indicate how close a person was to a fired gun. </li></ul><ul><li>Rifling (grooves) in a gun barrel causes distinctive grooves, indentations and scratches upon fired bullets, which can be matched to the weapon that fired them. </li></ul><ul><li>Police are able to search the Integrated Ballistics Identification System (IBIS) database to compare markings from bullets, cartridge cases, and shotgun shells to ballistic evidence. </li></ul>Investigators can compare the striations on bullets to see if they match.
  64. 72. <ul><li>Glass </li></ul><ul><li>• Glass particles can be found at various crime scenes, such as breaking and entering, hit and run, vandalism, or murder.  </li></ul><ul><li>• Glass at a crime scene is analyzed to determine its color, surface characteristics, tint, thickness, density, chemical composition, and refractive index (RI). </li></ul><ul><li>The results of the tests provide clues about the crime and help investigators connect the evidence to a suspect or other object used in a crime, such as matching glass from a crime scene to a headlight to a suspect’s car. </li></ul>Magnified image of glass fragments The pattern of cracks in a windshield fracture can reveal information about speed, occupant position, and angle of impact.
  65. 73. Impression Evidence Shoeprints & Tire Tracks •  Impression evidence can be photographed, lifted with tape, or cast with plaster to compare to a suspect’s shoes or tires. •  Investigators will examine the evidence to identify the brand of shoe or tire based on its tread pattern and other physical features to provide leads in the case. •  Shoes and tires will also show wear patterns after being used for a period of time as well as other features (scratches, nicks, and cuts) that can be used to match evidence to specific items. For example, shoeprints can be matched to a suspect based on how the treads on the shoes that are worn down due to that person’s walking style. Tool Marks •  Tiny nicks and chips form on the edges of a tool as it is used, which can be used to identify matches between evidence and suspects. •  Tools may also pick up traces of blood or other substances that can be tested or have fingerprints that can be lifted. Bite Marks • Each of the 32 teeth in humans is unique due to age and wear. • Impressions and photographs of bite marks left on a victim, assailant, or other object at a crime scene can often be matched to dental records.
  66. 74. <ul><li>Paint </li></ul><ul><li>Physical and chemical analysis of paint evidence (chips or residue) can indicate it’s class , such as automobile paint, house paint, nail polish, etc. The evidence can be compared to 40,000 different types of paint classified in a database, which can be used to identify a particular make or model of car or brand of tool. </li></ul><ul><li>Paint evidence can also indicate individual characteristics if an investigator is able to find similarities between two samples, such as the color, number of layers, chemical composition, or a physical match between the edges of two paint chips – one from a tool and one from a crime scene. </li></ul>Paint Layers Physical Match of Paint Chip Edges Paint Transfer on a Car
  67. 75. Tool Marks Matching tip of knife found in victim With knife found in suspect’s pocket Striations across plastic bags; R one found around victim’s Head L one found at suspect home
  68. 76. <ul><li>Fracture Matches (Vehicle Lights) </li></ul><ul><li>• When an object broken, torn, or cut, two unique edges are formed, which are referred to as fracture lines. </li></ul><ul><li>These edges can be compared by the naked eye or with microscopes to see if they fit together , which indicates that they may have been part of the same object at one time. </li></ul><ul><li>•  Investigators may compare the edges on pieces of tape, glass fragments, paint chips, pieces of a car from an accident, paper bag, etc. to find possible matches. </li></ul>
  69. 77. DNA •  Investigators can extract DNA from almost any tissue, including hair, fingernails, bones, teeth and body fluids. The DNA is used to create a profile that can be compared to profiles from suspects or victims. •  CODIS (Combined DNA Index System) is a database maintained by the FBI that is used to find matches to unknown DNA samples from a crime scene. <ul><li>Insects </li></ul><ul><li>Flies, beetles, and other insects can provide useful clues about a corpse. </li></ul><ul><li>Forensic entomologists use factors such as weather conditions, the location and condition of the body, and their knowledge of the life cycles of insects to help them estimate the postmortem interval or PMI (the time between death and the discovery of the body). </li></ul><ul><li>  </li></ul>