incriminating marks part 1. what are we looking at? imprints vs. impressions imprints vs....
Post on 01-Apr-2015
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Incriminating MarksPart 1
What are we looking at?
Imprints vs. ImpressionsImprints vs. Impressions Very real differences Very real differences Determining the difference can determine Determining the difference can determine
how the evidence is collectedhow the evidence is collected
Imprints
Is a two-dimensional pattern on a hard Is a two-dimensional pattern on a hard surfacesurface Examples:Examples:
Impressions
Is a three-dimensional indentation or patternIs a three-dimensional indentation or pattern Formed when an object presses into a Formed when an object presses into a
softer surface.softer surface. Examples: Examples:
Information Specific to Shoeprints
Can be impressed or Can be impressed or ““visiblevisible”” Many Different Ways to collect this Many Different Ways to collect this
evidenceevidence Many Different Factors involved in the Many Different Factors involved in the
analysis of this evidenceanalysis of this evidence
Types of Shoeprints
Visible (Imprint)Visible (Imprint) Stepped into something, then onto Stepped into something, then onto
somethingsomething Impressed (Impression)Impressed (Impression)
Stepped into somethingStepped into something
How to collect Imprint Evidence
Many different ways to collect, based on Many different ways to collect, based on the type of shoeprint it isthe type of shoeprint it is Electrostatic LiftingElectrostatic Lifting Gelatin and Adhesive tape liftingGelatin and Adhesive tape lifting PhotographyPhotography Powdering and ImprintsPowdering and Imprints Chemical EnhancementsChemical Enhancements
Electrostatic Lifting
Used for lifting Used for lifting ““VisibleVisible”” Shoeprints Shoeprints Uses Electricity to place a charge on the particles Uses Electricity to place a charge on the particles Used on many different surfaces: almost Used on many different surfaces: almost
everythingeverything
Video of LiftingVideo of Lifting
Chemical Enhancement
Tests on the residues found within the Tests on the residues found within the imprintsimprints Examples of what can be found is:Examples of what can be found is:
How to collect Impression Evidence
PhotographPhotograph
CastingCasting Is done differently depending on the Is done differently depending on the
location of the impressionlocation of the impression
How to make a castHow to make a cast
Comparing Evidence
Most importantMost important FIND THE ORIGINAL FIND THE ORIGINAL OBJECTOBJECT This is the This is the ““known standardknown standard””
Database of shoe and Tire treads – used to Database of shoe and Tire treads – used to exist! Law enforcement only has it now. exist! Law enforcement only has it now.
Analysis of Evidence
3 Major steps to examining evidence3 Major steps to examining evidence Determine what made the prints (class)Determine what made the prints (class) Determine the (individual) characteristics Determine the (individual) characteristics
of the printof the print Comparing to Known StandardsComparing to Known Standards
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