Unit 3 - Shoe + Tire impressions

Difference between 2D and 3D shoe imprint:

2D is patent e.g. footprint is in blood

3D is plastic e.g. cast can be made from footprint

How should footprints be photographed?

1. Measure length + width

2. Sources of light are shined at low angles on the footprint to give more depth

3. Tripod is placed 90 degrees above the footprint to take photo

What information can be gained from fingerprints?

1. Sex: male/female

2. Height of the person

3. Entry and exit of the location

4. Whether suspect was running/limping

5. Whether suspect was carrying something heavy

6. Size, type & make of shoe

Examples of class features in a fingerprint include:

1. Logos

2. Pattern of shoe

Examples of wear features include:

fading/discoloration/over pigmentation at any part of the shoe

Examples of individualizing/accidental/minutiae characteristics include:

1. Neutral pronation

2. Over pronation

3. Under pronation

Neutral pronation

even wear patterns on the footprint

Over pronation

Wear patterns on the inside of the body (top left + bottom right)

Under pronation/supination

Wear pattern on the outside of the shoe (pointing away from the body)

Footprints of a man

Toes are pointed slightly outward/straight

Footprints of a women

Toes are slightly pointed inwards

Footprints of someone carrying load

Prints are consistently deeper on one side, then person is carrying load on that side

Footprints of someone running

Footprints are deeper on the front foot than the back foot and stride is long

Tread blocks

Sipes

Grooves

Pitch length

distance until a pattern repeats itself

Directional tread design

• designed to roll forwards not backwards

• snow tires + wet weather tires have this design

  • tires channel water/snow away

• V shape formed by grooves

Non directional symmetrical design

• left and right side are mirror images

• no specific direction of rotation

Asymmetric tread design

• both halves have different pattern

• best for turning ability

Individualizing minutiae

• wears and tears

• foreign object e.g. stone

Problems with tire evidence:

1. Surface conditions need to be good

   • hard packed sand —> better

   • softer sand —> worse

2. Material can “blow into” or fall back into impression

Note: Physical impressions of tires on human skin is possible