footwear impression evidence-Will

Question 1

latex derived rubber

Answer 1

vulcanised to increase hardness
environmentally friendly
huge range of working temperatures

Question 2

polyurethane

Answer 2

variable air bubble content for shock absorption
thermo-set
often used as midsole material as foams

Question 3

thermoplastic rubber

Answer 3

hard wearing

common

Question 4

PVC

Answer 4

includes chemicals to prevent stickiness at high temperature

chemically resistant, but sticky when warm

Question 5

Ethyl vinyl acetate

Answer 5

excellent shock absorption

commonly midsole material as foam material

poor wearing characteristics

Question 6

molding process

Answer 6

completed sole formed in a mold

Question 7

cut process

Answer 7

sole is cut from pre-made sheeting material

Question 8

compression molding

Answer 8

solid plymer material placed into the mold

mold closed, compressed and heated

excess materal leaks around the edges-flashing

cycle may take up to 10 mins

Question 9

injection molding

Answer 9

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

Question 10

plastic 3D impressions

Answer 10

variable in quality - dependant upon material texture and stability

may contain contaminants which obscure detail

longevity variable
-rain = stability depends upon medium

Question 11

casting plastic 3D impressions

Answer 11

casting will destroy the impression

life size 1:1 scale allowing a direct comparison

shows very fine detail

dental stone
-produces high detail, high strength

paraffin wax
-marks in snow
-causes immediate melting of impression
bubbles

sulphur

• marks in snow
• causes immediate melting of impression
• fragile
• H&S implications

Question 12

give 4 examples of smooth non-porous surfaces

Answer 12

floor tiles
glass
gloss painted surfaces
laminate floor

Question 13

give 2 examples of smooth porous surfaces

Answer 13

untreated wood

emulsion surfaces

Question 14

enhancement

Answer 14

improves contrast between the medium and the mark

improves outcome of identification

chemical

powders and suspensions

physical lift

• ESLA
• gel lift

alternative light source

Question 15

chemical enhancement

Answer 15

thiocyanates

• iron in solid residue will react to form red/brown colour
• good for wet origin marks

8-hydroxyquinoline

• reacts with some metallic ions to produce UV fluorescence -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
• will subline

bromophenol blue

• turns from yellow to blue above pH 4.6
• good for some dry origin marks

Question 16

enhancement for marks in blood

Answer 16

leucomalachite green
-colour change to green

luminol/blue star
-production of luminescence visible in darkened area

leuco-crystal violet
-colour change to violet

kastle-meyer
-colour change to pink

acid yello-7

acid black 1

acid violet 17

Question 17

chemical enhancement for blood

Answer 17

suspected bloodstains first fixed

• commercial blood fix
• sprayed

dyed

• covered in absorbent material
• material covered in dye and left for 30 mins

wash
-dye washed off and dabbed with absorbent material

Question 18

other enhancement techniques

Answer 18

powder enhancement

vacuum metal deposition

superglue fuming

Question 19

what does ESLA stand for?

Answer 19

electrostatic lift apparatus

Question 20

ESLA

Answer 20

designed to lift dry origin dust impressions from a surface
limited use for damp or wet origin marks
best used when a surface medium cannot be removed

Question 21

ESLA method

Answer 21

film places 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

Question 22

ESLA issues

Answer 22

limited success with some types of mark

unless the film is well stored
-continues to attract ambient dust particles

Question 23

gel lift

Answer 23

gelatine based adhesive surface
a low tack solution for lifting dry/wet impressions
inferior to ESLA for dry impressions
superior to adhesive and can lift from various media
ideal for powdered impression
best used when a surface medium cannot be removed
gel may be coloured to improve mark contrast

Question 24

name an issue with gel lift

Answer 24

loses tack over time

Question 25

alternative light sources

Answer 25

crimelites or Quasar

marks may be visible under illumination at appropriate wavelength

simple oblique is most reliable lighting technique

Question 26

photography

Answer 26

marks and 3D impressions respond well to oblique lighting

shield from ambient lighting

Question 27

name 3 footwear databases

Answer 27

NFD
Solemate and SICAR
FIT

Question 28

class characteristics

Answer 28

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

Question 29

Shallamach wear

Answer 29

known as feathering

caused by abrasive forces

rubber shaped into wave like formations

similar to friction ridges

very short lived

Question 30

wear characteristics

Answer 30

short

• wear marks consistent
• some additional wear possible but unlikely

medium

• consistency poor
• additional wear features more likely
• original wear features spread

long
-footwear unlikely to be in circulation

Question 31

identifying characteristics

Answer 31

random events giving rise to a unique characteristic found on only that shoe