Tyre marks

Question 1

What 6 things can tyre marks tell us?

Answer 1

tyre type

• all terrain
• high-performance
• winter

Make

• michelin
• bridgestone
• goodyear

Model
-optigrip

size of tyre

track width

wheel base

Question 2

What is the track width?

Answer 2

distance between left and right tyres

Question 3

What is the wheel base?

Answer 3

the distance between front and rear tyres

Question 4

Tyre mark evidence

Answer 4

subject to deformation or destruction

• other vehicles
• rain
• wind

ability to find unknown suspects may be limited

• stronger than footwear = PNC/DVLA
• can provide extremely useful intelligence

Question 5

What are the 4 types of impression.

Answer 5

3D impression
positive impression
negative impression
other impressions

Question 6

What is a 3D impression?

Answer 6

impressions in soft ground

Question 7

What is a positive impression?

Answer 7

residue from the tyre is deposited into a surface and remains

Question 8

What is a negative impression?

Answer 8

tyre removes material from a surface

Question 9

Give an example of an other impression?

Answer 9

tyre marks on body of victim

Question 10

What is a treatment for 3D impressions?

Answer 10

cast

Question 11

What are 3 treatments for wet impressions?

Answer 11

powder
alternative light source
chemical treatment

Question 12

What is a treatment for dry impressions?

Answer 12

lift

photography in situ

Question 13

What two features of tyre marks help to identify the size of the vehicle?

Answer 13

track width

scene marks

Question 14

e.g. 155/70 R13 75 T

What does the 155 represent?

Answer 14

section width (mm)

Question 15

e.g. 155/70 R13 75 T

What does the 70 represent?

Answer 15

aspect ratio

Question 16

e.g. 155/70 R13 75 T

What does the R represent?

Answer 16

radial tyre type

Question 17

e.g. 155/70 R13 75 T

What does the 13 represent?

Answer 17

wheel rim diameter

Question 18

e.g. 155/70 R13 75 T

What does the 75 represent?

Answer 18

load index

Question 19

e.g. 155/70 R13 75 T

What does the T represent?

Answer 19

speed rating

Question 20

Reference tyre mark impressions

Answer 20

tyres should be fitted to suspect vehicles

car/driven/rolled across a section of inked paper onto a section of thick paper

thin layer of vaseline applied to tyre and driven or pushed over thick paper

Question 21

What are the problems with mould characteristcs?

Answer 21

non unique

• specific to a single tyre mould
• features may therefore be present on numerous tyres
• the sipe is not fully formed
• damaged mold

not conclusive
-does not provide support

Question 22

What are identifying charactersitcs?

Answer 22

cuts/abrasions

nail or screw head

holes-perforations

trapped material-stones

Question 23

Conclusion of characteristics

Answer 23

class
-size consistent with scene

sub class
-missing spieling mark consistent with scene

identifying characteristics

• generally consistent
• some missing marks
• may have been lost due to additional wear