Impression Evidence Exam 1 FIVS 220

Bill Bodziak

FBI tire and footwear expert

wrote the textbook

Paul Kirk

microscopy specialist

Edmond Locard

father of forensic science

created the Locard Exchange Principle

“It is impossible for a criminal to act, especially considering the intensity of a crime, without leaving traces of this presence”

basic shoe terminology

backstay

the back of the heel portion of the shoe

heel

and lifted platform on a shoe

lining

the inside of the shoe

quarter

the sides of the shoe

tongue

portion under the shoelaces

vamp

the flat portion on top of the toes

welt

the front portion of the toes

the scale of detection

under a comparison microscope, microstritae become visible

tire impression

a detailed section of a track that includes details about one tire

tire track

a long section of a path the car drove down. combined pattern of all tires

tire terminology

tire tread patterns

DOT serial number

DOT (plant code) (tire size code) (group of opt symbols with the MFR) (date of manufacture)

sidewall codes

DOT (retread) (retread code) (week/year)

tire construction

1. the building drum is made in collapsible sections so the tire can be removes

2. the liner is applied

3. ply 1 and 2 are applied

4. beads are set in place and ply ends are wrapped over them

5. the center of the drum is inflated to a predetermined diameter. this expands the center of the plys and brings the beads closer together

6. 2 belts are applied

7. the tread is applied

8. rollers press against the tire as the drum rotates. this stitches the parts tightly together

9. a green tire is the result from these steps

green tire formation

the green tire is placed in a mold and curing press assembly to cure it to its final shape

tread wear indicators

AKA wear bar

a raised rubber bar 1/16 of an inch (2/32) above the base of grooves of tire

DOT requires all tires to contain at least 6

noise treatment

tire industry created tire designs that vary the size/pitch design elements of tire

reduces and controls the noise emitted by tire

stress cycle

under load of a vehicle, rotating tire goes through stress

contact patch

portion of tire touching ground

women vs men shoe sizes

women sizes are men size + ~1.5

sizes 1.5 (5-6.5, 7-8.5 10-11.5…) may have the same outsole size

typical outsole length

8.46mm/each full size

4.23mm/each half size

Vitale Bramani/Vibram shoes

Quabaug

the largest shoe manufacturer

blown rubber/microcellular outsoles

the outsoles can burst from their molds and expand to a larger size

can be die cut to a particular shape and size

same size elements

larger sizes have more elements

graded elements

some elements stay constant and depends on the shoe size

tread depth by shadow length

EH = (SH x SL)/SS

EH = element height

SH = spike height

SL = shadow length

SS = spike shadow

tire track width

between 2 tires

front/front or rear/rear

center of wheel to opposite center of wheel

wheelbase dimensions

front to rear tire measurements

turning diameter

diameter of circle a vehicle makes when its steering wheel is fully turned

pertains to FRONT WHEELS only

(B²/A) + A

B = distance between 2 points on turn circle

A = distance between outer margin and a mid point between B points

Antilock Breaking System (ABS)

helps with skidding

automatically breaks and unbreaks the tires when slamming on breaks