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Lecture 17-18 Impression Evidence . General & Scene Considerations. Overview. Impression Evidence Anything that leaves an impression can be compared with an original Class Characteristics Marks produced during manufacture AND during routine use

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lecture 17 18 impression evidence

Lecture 17-18Impression Evidence

General & Scene Considerations

overview
Overview

Impression Evidence

Anything that leaves an impression

can be compared with an original

  • Class Characteristics
    • Marks produced during manufacture AND during routine use
      • Made during the manufacture of the tool or the object
  • Accidental or Unique Characteristics
    • Small (or microscopic) unique (accidental) marks are thought to be traceable to a specific object
    • Occur during normal useage
slide3

Classifying Footwear Impressions

  • Three categories:
    • Visible: Occur after someone steps into a foreign substance and then transfers the substance to a clean surface.
      • Depending upon the background color, a visible print may be a simple impression made from dust on the sole of the shoe.
    • Plastic: Occur when someone steps into a malleable (soft) surface and leaves a three-dimensional impression.
      • Typically, this could be an impression in mud or cement.
    • Latent:Those that are invisible to the naked eye and typically require an aided eye to make them visible.
slide4

General Characteristics of Impression Evidence

  • 2D Impressions
  • Defined as a pattern lying ON TOP of a surface
    • Latent (invisible)
    • Patent (visible). Examples are fingerprints, footwear impressions and tire tracks, among others.
  • Dust impressions are usually classified or defined as 2D impressions,
    • Actually three dimensional having very shallow depth and surface topology
slide5

3D impressions

  • Object impresses its pattern into a softer surface,
    • When tire makes pattern in wet mud.
    • The famous impression of Neil Armstrong’s footwear impression on the moon is an example of a 3D impression
slide6

Impression Evidence

  • Large, diverse group,
  • Expect at least one category present at most scenes.
  • Fingerprints – most prevalent
    • Next would be footwear and tire impressions
    • Bite marks (sexual assaults), lip prints and ear prints comprise another category but occur much less frequently.
    • Tool mark impressions is another large class of impression evidence that comprises several subcategories:
      • Screw drivers, saws, cutting tools (wire cutters) etc.
  • Ballistics evidence:
    • Bullet impressions,
    • Cartridge case impressions, and marks made by other
slide7

Categories of Impression Evidence

Fingerprints

Footwear Prints

Tire Tracks

Tool Marks

Bullet Marks

Cartridge Cases

Fired Weapon

Bite Marks

Ear Prints

  • Impressed prints
    • Shape of a tool
    • Striated impressions or striated marks/scraping marks
      • Scrapping of tool’s surface against receiving surface
slide9

A Class of Associative Evidence

  • Refers to its future use; to help ascertain the truth of alleged facts.
  • Footwear evidence = Associative evidence.
    • Helps investigators (police and prosecutors) and juries support contention that someone had been at crime scene.
    • Can identify which shoe left an impression ,,, can help place someone at the scene. ….
    • Alone, not determinative of guilt,
      • Help circumstantially toward that end.
      • Thus finding footwear evidence linked to an individual shoe can be critical evidence,
      • Used by a prosecutor during trial.
      • Also helpful for investigators to understand the veracity of witness or a suspect’s statements.
  • Locating footwear evidence: not easy … logic can point to the location where to search.
  • Time and effort spent locating, photographing, lifting and comparing impression evidence is critically important.
slide10

National Research Council 2009 Report

  • National Research Council of the National Academy of Sciences suggests that pattern (impression) evidence should be interpreted more carefully.
    • The report says that additional research is necessary in order to determine the underlying scientific basis of pattern evidence comparisons.
  • NRC committee also suggested there should be a statistical basis for making these comparisons, which currently, does not exist.
    • Practitioners do not universally agree that a statistical basis is necessary for making valid comparisons.
  • The NRC report does not say or imply that footwear comparisons are not valid nor does it say or imply that these comparisons have no forensic value.
value of impression evidence
Value of Impression Evidence

Laboratory Examinations Establish Links

Links to Other Crimes

  • Database searching
    • Footwear impressions from various crimes
  • Useful for investigations of repetitive crimes
    • Burglaries
      • Recidivism rate is high >50%
  • Multiple impressions
  • Absence of multiple impressions
    • Suggests a lone perpetrator

Minimum # of Perpetrators

  • Backtracking footwear impressions
    • Path of perpetrator
    • Discarded weapons or other evidence
      • Associate footwear with tire impression - lead to a vehicle

Association with Other Evidence

slide12

Entering a House

  • From the Outside
  • Defines residue type on shoe.
  • Subsequent steps transfers residue from shoe to carpet.
  • Forensic value not known until found and evaluated.
  • Example
  • Burglar enters a house through a window and steps onto a carpet,
  • What is probability that dirt residue from sole will leave an impression?

Entry Point 1

Entry Point 2

slide13

Hypothetical Murder Scene

  • Assume two burglars enter scene at different points,
    • Expect different footprints
      • ‘Entry Points ‘1’ and ‘2’.
    • If both footprints entering house at different locations had the same sole pattern (class characteristics)
      • Suggests @ least two people involved.
      • Remote possibility that same person entered on separate occasions.
        • Close examination of the size and other characteristics might dispel that argument.
  • Using the same logic, suppose a third unknown fingerprint was found inside the house.
    • Suggests a third perpetrator.
why impression evidence is overlooked or not found
Why Impression Evidence IsOverlooked or Not Found
  • 1. Not aggressively looking for
    • Belief can’t be found
    • Incomplete understanding of value
  • 2. Incomplete search of scene
    • Inability to find points of exit/entrance
  • 3. Lack of Understanding a Class of Fragile Evidence
  • 4. Lack of knowledge of How to Collect and Preserve

Training

1. Weather Obliterates Outside Prints

2. Surface Characteristics not Conducive to

Production of Impression Evidence

3. Scene Entrance Only Access to Scene

Scene

1. Initial Scene Responder Obliterates

2. Public Obliterates Before Authorities Arrive

Other

types of 2d impressions
Types of 2D Impressions

Wet Residue Impressions

Dry Residue Impressions

Made from Dust

Made from a Wet Slurry

2 d impressions
2-D Impressions
  • Most found on floor surfaces
    • Magazines/newspapers,
    • Tile floors
    • Dust prints on carpets
    • Shoe prints on doors
    • Stepped-in grease/oil/blood
  • Requires careful inspection/search of scene
    • A category of fragile evidence
    • One of the first activities
  • Impression transfers vary
    • Clean shoes leave impressions on paper/glass/countertops/furniture
    • Dirt and/or dust
    • Wet grass
    • Grease, oil, wax or furniture polish
    • Blood or other fluids.
  • Visibility of an impression
    • Contaminating material deposited by shoe
    • How it contrasts w/a surface
  • All impressions are potentially identifiable
  • Often, less visible impressions leave more detail
slide19

Intellectual On-Scene

Impression Evidence Checklist

  • ALWAYS Expect Impression Evidence.
  • Study the Scene!!!!!
  • What is the likelihood of finding probative impressions?
    • Where would they likely be?
      • Are they wet or dry residue impressions
      • Would they be plastic, latent, visible?
    • What is the strategy for archiving?
      • Is it necessary to enhance them?
      • Can they be lifted?
    • How should they be preserved?
slide20

Impression Prints @ Crime Scenes

Spilled Blood

Victim’s Clothing

Point of Occurrence

Furniture

Floors

Strewn reading material

Areas of Struggle

Windows

Adjacent areas outside

Point of Entry/Egress

Struggle-to-Victim to Exit Point

Path Through Scene

On Doors – kicked in

Other Footwear Patterns

Landscaping

Driveways

Walkways

Outside

slide22

Following Footprints

Through the Scene

Bodziak: Footwear Impression Evidence, 2nd Ed, CRC Press, New York