Shooting scene investigation Flashcards
Reconstruction
The process of utilising information derived from physical evidence at the scene, analyses of physical evidence, and interferences drawn from such analyses to test various theories of the occurence of prior events
Re-enactment
Is but a demonstration of a previously existing reconstruction based on conjucture rather than scientific principle
What are the possible outcomes of a bullet impacting a surface
The bullet remains intact and passes through causing identifiable entry and exit wounds
The bullet remains intact but does not pass through, there is an entry but no exit hole
The bullet does not remain intact and some, or all the fragments are either retained or pass through
The bullet bounces off either intact or fragmented
Indicators for the use of firearm
Bullet, cartridges, of fragments
GSR deposits, but only at close range and subject to confirmation tests
Wipe ring around hole
Size and shape of the hole
Evidence of high energy penetration and damage highly local to the hole, which depends on the material
Metal penetrations
Bullet impacts on metal are easily distinguishable
They leave neat margins on the entry side of the hole and the exit looks like a truncated funnel
If the metal plate is thick there might just be a dent but paint or other surface coatings may be disrupted
Wood and frangible penetrations
Present a neat hole on the entry side
Catering and splintering
Low velocity creates significant splintering whereas high velocity makes a neater hole
Soft wood splinters less than hard wood
Plywood will delaminate with sections of the back layer being torn away
Glass penetrations
Order of impact for multiple bullets can be figured out
High velocity bullets leave small neat holes with little fracturing
Low velocity is the opposite
Concentric - circular ring cracks
Relatively straight radial cracks
Fabric penetrations
Gun shot residue will be present if its a close range shot
May get a bullet wipe ring
For synthetic fabrics, microscopic examination at the edge of the hole will show evidence of individual fibres melting, resulting from frictional heating
For natural fabrics- it will reveal fibres with shredded and frayed ends around the hole
Evidence from a firearm user
Flash burns including GSR on skin
Burns to fabrics and flammable surfaces
Imprints and impressions - ricochet damage
Bullet wounds - also includes wounds from debris
Hearing damage
Slide bite
This is where the recoiling slide on a SLP cuts the web between thumb and index finger on the hand holding the weapon
This is from holding the firearm too high on the pistol grip
Hammer bite
SLPs with an external hammer can pinch the web between the thumb and finger
Could be DNA left on the chequered hammer
Where was the shooter in the scene
Eyewitness accounts
Bullet trajectories and velocities
Gunshot residue
Cartridge ejection patterns
String Trajectory lines
Inexpensive and easy to use
Must be kept tensioned so require anchoring
Line is passed through the centre of the bullet hole and then extended to show the path.
Laser trajectory lines
useful for non-penetrating impacts.
Can be left in place
Can be used to align objects that have been moved
Hard to photograph
Can be unstable and divergent
Cartridge ejection patterns
Dependent on:
Weapon design
Weapon condition
Ammunition type
Position weapon is held when fired
Movement of weapon during firing
How tightly a weapon is held during firing
Type of terrain where shooting occurred
Presence of obstacles at scene
