incriminating marks part 1. what are we looking at? imprints vs. impressions imprints vs....

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