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Imaging and Photography > Footwear Impression Evidence > Flashcards

Footwear Impression Evidence Flashcards

1
Q

footwear anatomy

A 
midsole
sole- area of she most likely to leave a mark
upper
toe box
toe cap
throat
tongue
quater
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2
Q

the sole

A

Can be made from a variety of materials:
An understanding of materials and processes is essential

Latex derived rubber – e.g. Vibram

  • Vulcanised to increase hardness – Hard wearing
  • Environmentally friendly

Polyurethane – Variable air bubble content for shock absorption

Thermoplastic rubber (TPR/TPE) – Rubber/plastic property
Various shoe types
Fairly hard wearing

PVC – Includes chemicals to prevent stickiness at high temperature
Chemically resistant, but sticky when warm

Ethyl vinyl acetate (EVA) – Excellent shock absorption
Commonly midsole material as foam material

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3
Q

manufacturing

A

manufactured either by:
Molding processes – Completed sole formed in a mold

Cut processes – Sole is cut from pre-made sheeting material

Completion by combination processes also quite common

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4
Q

sole manufacture- compression molding

A

compression molding

  • material placed into the mould
  • mould closed, compressed and heated
  • Excess material leaks around the edges – Flashing
  • Cycle may take up to 10 minutes in some cases
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5
Q

sole manufacture- injection moulding

A
  • Soling material injected in liquid form into a closed mold
  • Air holes allow efflux of trapped air – Characteristic flashing
  • Formed soling sometimes directly attached to uppers at the same time as the molding process
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6
Q

footwear mark impressions

A

Present in up to 60% of crime scenes

Intelligence
Excellent ability to link multiple scenes
Poor ability to identify unknown offender

evidential

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7
Q

footwear mark impressions

A

Often difficult to locate
Easy to miss

Often overlooked

Recent drive to improve results and awareness
Centre for applied Science and Technology (CAST)

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8
Q

plastic 3D impressions

A

variable in quality
Dependant upon material texture and stability
- Clay soils (if damp) in particular hold marks very well

May contain contaminants which obscure detail

  • Small stones, plant detritus etc.
  • Never remove these (unless you can guarantee no harm will come to your mark), but note their presence and location
Longevity variable
Rain – Stability depends upon medium
Wind – Unlikely to be a big problem in most cases
Snow
Access to other pedestrians
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9
Q

3D impressions treatment and casting

A

Treatment
Photography – Scale

Casting
Life size – 1:1 Scale allowing a direct comparison to footwear or a reference mark
Shows very fine detail –

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10
Q

3D impressions casting

A

Dental Stone
Produces high detail, high strength casts which are cheap

Paraffin Wax – Marks in snow (not UK)
Causes immediate melting of impression
Bubbles
Contraction an issue therefore not 1:1

Sulphur – Marks in snow (not UK)
Causes immediate melting of impression
Fragile
H&S implications
Contraction one again an issue
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11
Q

surfaces

A 
types
smooth non porous
- floor tiles
- glass
-gloss painted surfaces
- laminate floor

smooth porous- some loss of detail due to surface topology

  • untreated wood
  • emulsion surfaces

other surfaces- variable

  • carpet
  • patterned/stippled surfaces
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12
Q

marks

A

Patent or latent

Latent marks may only be visible under certain lighting – Oblique

Consist of a variety of substances
Dust, powder, ash, dirt, soil  
Oils, waxes
Water  
Blood

May be of wet or dry origin
This should inform your treatment of the mark

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13
Q

enhancement

A

Improve contrast between the medium and the mark

Improves the outcome of identification

Some techniques potentially destructive therefore…

Photograph the mark before enhancement

Consider testing any chemical or powder technique on a small lower quality area of the mark before committing

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14
Q

enhancement techniques

A

-Chemical
- Powders and suspensions
- Physical Lift
ESLA
Gel Lift
- Alternative light source
Quasar, Crimelite (82L)

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15
Q

chemical enhancement

A
  • Thiocyanates
    Iron in soil residue will react to form red/brown colour
    Good for wet origin marks
  • 8-Hydroxyquinoline
    Reacts with some metallic ions to produce U.V. luorescence – Aluminium
    Wet or dry origin marks
  • Physical developer
    Silver deposited preferentially on waxy materials

-Iodine*
Vapour will cause a yellow/brown colour change in waxy or oily materials

-Bromophenol blue
A pH indicator! Turns from yellow to blue above pH 4.6 – dry origin marks

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16
Q

enhancements for marks in blood

LMG

A
  • Leuco malachite green (LMG)

Colour change to green in presence of blood

17
Q

enhancements for marks in blood

Luminol/blue star

A
  • Luminol/Blue Star

Production of luminescence visible in darkened area

18
Q

enhancements for marks in blood

KM

A

Kastle-Meyer (KM) – Colour change to pink

Peroxidase activity

19
Q

enhancements for marks in blood

Leuco crystal violet

A

-Leuco-crystal violet (LCV)

Colour change to violet

20
Q

enhancements for marks in blood

Acid …

A

-Acid Yellow 7 – Yellow stain

Acid black 1 – Black Stain

Acid Violet 17 – Violet Stain

-protein stains which responds well to marks in blood giving marked enhancement of contrast

21
Q

chemical enhancement for blood

A

Method

Suspected bloodstains first fixed
ensure the mark doesn’t run

Dyed
Covered in absorbent material
Material covered in dye and left for 30 mins

Wash
Dye washed off and dabbed with absorbent
material

22
Q

powder enhancement

A

-Provide maximum detail and contrast against surface
-May work well with damp or tacky (wet origin) marks
- An alternative is the use of powder suspensions
Powder/Detergent/Water such as SPR

23
Q

vacuum metal deposition

A
  • Rarely used for the enhancement footwear marks
  • Expensive
  • Few chambers available in UK
  • Lab only
24
Q

superglue fuming

A
  • Not commonly used for the enhancement footwear marks due to the practicalities of ‘at scene’ fuming
  • May be very effective in some cases
  • Generally lab based technique
  • Portable fuming apparatus is available but practicality is somewhat limited and there are H&S concerns of producing CA fumes in situ
25
Q

ESLA

A

Electrostatic lift apparatus
A device designed to lift dry origin dust impressions from a surface

Operation

  • Film placed over mark
  • Device connected to film and also to ‘ground’
  • Uses a build up of static charge in the film to lift particles from the mark onto the film surface
26
Q

ESLA issues

A
  • Limited success with some types of mark
  • Unless the film is well stored
    It continues to attract ambient dust particles until the mark is eventually hidden!
  • ESLA film should be kept out only as long as is necessary
  • Storage
    Often stored in flat ‘pizza’ boxes to minimise contact with dust
    Can be rolled – May produce loss of evidential material
27
Q

Gel lift

A

A gelatine based adhesive surface

  • A low tack solution for lifting some dry/wet origin impressions
  • Ideal for powdered impression
  • Best used when a surface medium cannot be removed
  • Gel may be coloured to improve mark contrast
    Black
    White

Issues
-Loses tack over time

28
Q

alternative light sources

A

Crimelites or Quasar

  • Marks may well be visible under illumination at an appropriate wavelength
  • Fluorescent properties may allow visualisation
  • Simple oblique
    The simplest and perhaps most reliable lighting technique for latent footwear marks
29
Q

photography

A
  • Get the best image that you can get
  • Never rely on software to improve a poor image
  • Take as many shots as you need
  • The photograph may be the only record if other techniques fail but you need to use a scale!

Lighting is crucial to get a good image
- Marks and 3D impressions will respond well to oblique lighting

30
Q

what can a footwear mark actually tell us

A

no reference

  • shoe type
  • make
  • model
  • description
  • possible size
  • can link scene to scene

with reference

  • can yield a positive match
  • extremely strong evidence
31
Q

footwear database

A

National footwear reference collection (NFRC) has since 2009 ensured a nationally agreed coding system for footwear

Numerous examples of software

  • NFD – National footwear database
  • Solemate and SICAR
  • FIT (Footwear intelligence Technology)
32
Q

reference marks

A

shoes donated by a suspect

33
Q

class characteristics

A
  • repeatable characteristics shared by many or all shoes of the same type or class
  • it only takes a single point of difference for an elimination
34
Q

wear characteristics

A

influenced by:

  • walking style
  • weight
  • anatomy

fundamental state of wear should approximate scene mark

wear appears do not constitute positive ID
except shallamach wear

35
Q

shallamach wear

A

often known as feathering

  • caused by abrasive forces
  • very short lived
36
Q

wear characteristics

A

time between scene mark and reference

  • short (days/weeks)
    wear marks consistent

-medium (weeks/months)
consistency poorer

-long (months/years)
variable consistency

37
Q

combined class characteristics

A

-Repeatable characteristics shared by many or all shoes of the same type or class

Despite this, certain features may be present in only a proportion of shoes

  • Many shoes are made from a number of separately molded sole elements
  • these are brought together and assembled to form a completed shoe

for each element of the shoe there may be a number of moulds

38
Q

identifying characteristics

A
  • a unique characteristic found on only that shoe

- must be created by a random ‘unrepeatable’ event

Imaging and Photography (20 decks)

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