CRIM 355

• Tool marks, firearms
• Comparison/physical matching 
• RCMP lab - Vancouver - 7 People
• Need atleast a B. Sc. Hon engineering or science, including chemistry 
• 2-year understudy program

• Firearms and ammunition
• Toolmark identification
• Autopsy attendance
• Gunshot residue sampling
• Reconstructions
• Physical Matching 
• Serial number restoration
• Spark plug matching

• ANY hard object that leaves a mark in a softer object
• May be an actual tool
• May be a foot print in blood
• Hence, any harder objects leaving a marker in a softer objects

• 1. Impressed tool marks:
• -Tool pressed into objects
• -No movement involved

• 2. Striated tool marks
• -Pressed into object then removed
• -Sliding motion

• Can indicate the group that the tool came from (e.g. width of the blade, shape)
• Can eliminate but not identify to a single source
• Tool mark may not include entire tool

• MUST compare like to like 
• NEVER place suspect tool in mark 
• Take impression in a soft substance
• Compare the tool marks

• Class characteristics
• -are they the same?
• -do they eliminate?
• Individual characteristics
• -How many
• -Usually at least 7-8 matches needed

• Combo of class and accidental characteristicsHow manufactured?
• Every difference can be explained

• A significant and unique similarity must exist between the test and suspect tool mark
• Class and individual characteristics must agree
• NO unexplained differences must exist

• Was bullet fired from this gun?specialized form of tool mark examination
• Barrel is a tool that marks the bullet, breech face
• Firing pin, chamber, extractor ar tools

• Bullet-"slug"
• Usually lead
• May have a jacket - full metal jacket - prevent fragmenting

Roach - hollows out solid bar of steel - to make a barrel Leaves small scratches as it does each one, picks up dirt, loses dirt, etc ---> each barrel is unique

• Rifling is added
• Rifling - spiral grooves:
• -Puts spin on bullet (prevents tumbling)
• -Puts mark on bullet - Class and accidental

• Each manufacturer different - go clockwise or counter clockwise
• Grooves-cut bit, and lands

• Must compare like with like
• Is the gun safe to fire
• DO NOT clean it
• Test bullet fired into water
• Test bullet compared with suspect bullet

• Class characteristics
• -Same number of lands and grooves?
• -Same direction?
• -Caliber of bullet-original width of barrel before rifling
• Accidental (individual) characteristics
• -Use
• -Manufacture

• Can determine position of antagonists
• Distance apart
• Ammunition propelled by expanding gases
• Burned, Partially burned and unburned powder 
• MUST have suspect weapon AND suspect ammunition
• Fire into similar material at different distances

• Unburned powder inside woundStellate tearing
• Bullet wound surrounded by rim of vaporous lead
• Fibres may be melted

• Halo of vaporous lead around wound
• Unburned powder around wound

Only soot deposited

• Scattered specks of unburned and partially burned gunpowder grains 
• Stippling
• No soot or blackening, or vaporous lead

• NO residue on target
• Bullet wipe - on  edge of wound - wiped off bullet as it entered flesh

• If do not have suspect weapon and ammunition, can only make general conclusions
• Ammunition
• Weapon
• Silencer?
• Was bullet fired though something?

• Early tests – Dermal Nitrate Test
• Gunpowder
• Nitrates – in urine, cosmetics, tobacco
• False positives
• May just have been standing nearby
• Easily washed off

• Now test for Primer Residue:
• lead styphnate, barium nitrate & antimony sulfide
• Specific
• May be transferred by handling – look at amount
• Still easily washed off

• Why is bullet wound so much worse than knife wound?
• Temporary Cavity:
• Massive stretching due to gases expanding
• Briefly, very massive wound, much bigger than projectile
• Permanent Cavity:
• Actual damage to tissue

• Hollow point – mushrooms on contact – large wound
• Civilian ammunition – NO full metal jacket – mushrooms, fragments, great stopping power – hunting
• Military – full metal jacket - injure