Toolmarks, ‘Other’ Marks, Physical fits & Physical features

Question 1

What are toolmarks?

Answer 1

• Burglary
• Criminal damage
• Murders
• Kidnapping

Question 2

Type of mark

Answer 2

Impressions
- Mark pressed on surfaces
- Credit cards
- Engine numbers

Striated marks

Dynamic marks
- Inc marks left by bullets
- Saw marks

Question 3

What are the two general types of cutting action

Answer 3

• A squeezing action- seen with tools like bolts cutters, wire cutters, pliers
• Shearing/scissors action - seen with tools such as scissors, shears, snips

Question 4

How would you recover at the scene

Answer 4

Casting/Recovery
- What & Where to recover
- Cast may contain other evidence i.e paint

Question 5

What are the features when comparing?

Answer 5

Class features
- Common to all tool/items of a particular type
i.e flat headed screwdrivers

Subclass features
- Allows discrimination between groups of tools
i.e size or other manufacturing detail

Identification features
- Allows identification of a specific tool
- Random featured acquired via manufacture or use
i.e grinding detail or damage

Question 6

What are related evidence?

Answer 6

• Paint
• Flesh
• Blood?
• DNA

Question 7

What marks other than toolmarks?

Answer 7

• Tyre marks
  Similar to footwear marks but more complicated to examine

-Glove marks
Mostly impressed marks
Different depending on the type of glove

Question 8

Three categories of tyre marks

Answer 8

• Latent
  not visible to the naked eye
• Visible
  clearly visible - variation of quality
• Plastic
  3D prints in soft substrate

Question 9

Tyre Marks - Latent

Answer 9

E.g dusty tyre mark on cardboard box
Lifted using gel and photographed

Can be chemically treated to enhance
- similar to fingerprints
- tyre marks with protein
- DFO or ninhydrin

Question 10

Tyre marks - Visible (+ and -)

Answer 10

Positive: material i.e blood deposited by the tyre on a clean surface

Negative: material removed from a “dirty” surface by the tyre

Question 11

Tyre marks - Plastic

Answer 11

Made in soft material i.e snow, mud or sand

Photograph to recover or cast with dental stone
-> dental stone only good for short section
-> photography allows a recover of a whole thing

Question 12

What information can you get from tyres

Answer 12

Tyre patterns vary considerably between manufacturers and intended use of tyre

Basic tread info can help identify tyre type
- narrows down potential suspect vehicle

Tyres do suffer wear and random damage
- these features can allow identification

Suspect vehicle - prepare test impression from all 4 tyres