Topic 4 - Shooting Scene Reconstruction ('Bullet' Holes…
Topic 4 - Shooting Scene Reconstruction
the process of utilising information derived from physical evidence at the scene, analyses of physical evidence and conclusions drawn from such analyses to test various theories of the occurrence of prior events
Sketches of the incident scene and trajectories .
eye witness accounts
Cartridge ejection patters (if at scene)
a demonstration of a previously existing reconstruction based on conjecture (a guess) rather than scientific principle
Why Shooting Reconstruction?
Who, what when, where how and why?
cartridge case ejections
ricochets (rebound off a surface)
Provide a range of possible positions for shooter and victim to "paint the picture" of prior events.
To corroborate (confirm) or dismiss claims about a shooting for the courts.
To confirm a shooting actually took place:
bullet holes do not count, how do you know its a bullet hole?
do you have definite evidence of a firearm being used? Without it is a suspected shooting.
-Bullet remains intact:
passes through, identifiable entry and exit holes.
does not pass through, entry hole but no exit hole.
-Bullet does not remain intact:
some/all fragments retained in body or pass through.
-Bullet bounces off either intact or fragmented.
"the change in angle and/or direction of a projectile resulting from substrate contact."
V-shape left by lead/lead-nosed bullets.
Fracture lines left on painted surfaces.
Bullets can deform upon impact.
Bullets expand and spread and
as they scrape across surface.
can aid in determining shooter position. (suspects height, dominant hand, weapon position).
Direction of twist
is directly related to the side of the ricochet mark that the tail sits and also any lateral deflection observed.
Dense tissue will suffer more damage than hollow tissue - bone vs lung.
Elastic tissue will suffer less damage than rigid tissue - muscle vs liver.
Bone will suffer more damage than organ (hollow tissue) as it is more dense, alters projectile path.
Indicators for use of firearm:
bullets or cartridges.
GSR (close range only)
wipe ring around hole
size and shape of hole
evidence of high energy penetration
damage highly local to hole, depends on material.
neat entry hole
exit hole: truncated funnel
wipe ring on inside of funnel
Length of funnel depends on:
metal characteristics (too think = dent)
Wood and frangible/fragile materials:
neat entry hole
exit side: splintered, distributed debris
soft wood splinters
than hard wood (oak)
low velocity, large caliber = significant splintering on exit side
high velocity, small caliber = neater hole
radiating cracks will not propagate (grow) across an existing crack, thus can determine order of impact of the bullet holes.
high velocity bullets: neat holes, little fracturing
low velocity bullets: more damage
if aligned with wound, follow track
Synthetic fibres: microscope examination at edge of hole will show evidence of individual fibres melting, resulting from the momentary frictional heating caused by the bullet.
Natural fibres: microscope examination will reveal fibres with shredded and frayed ends around the hole.
bullet wipe (residue from barrel on bullet )
abrasion rings (close range < 6")
skull: inwards bevelling
star pattern (stellate) tissue disruption
long range shot distance
be determined. Shape of wound depends on impact angle.
larger bullet hole
skull: outwards bevelling
material projected outwards.
Evidence from Firearm and Shooter:
flash burns on user and target
GSR on shooter and target
burns to fabrics and flammable surfaces
imprints and impressions
Evidence Seen with
Recoiling slide on a SLP cuts the web between thumb and index finger on the hand holding the weapon, from mishandling the weapon.
Scope is designed to allow for recoil and inexperienced users do not know this, so when firing the scope hits them in the face due to recoil, leaving a crescent shaped mark.
SLPs with external hammer can pinch the web between the thumb and fingers. The mark can be matched to a specific hammer. Can also be DNA.
Rifles and shotguns will imprint on the shoulder and upper arm.
Handguns may imprint grip pattern on hand and wed of hand.
sin(A) = width / length
Or and inclanometer with
Can give muzzle to target distances (humane tissue markings).
Particulate: lift with acetate sheets or SEM stubs.
Precipitate: swab with distilled water and/or ethanol.
For Distribution Pattern:
Test suspect firearm with matching ammunition to recreate deposition pattern. This can reveal data: range and angle of shot.
Hot GSR particles travelling quickly can penetrate and produce bruising and/or burning on the skin. This marking is called
and is a series of dark spots around the
(60 cm or less). Density of tattooing is a fair indication of muzzle-to-target distance and can be compared with lab testing.
firing pin impression
ejection port dent
Cartridge Case comparison:
Test sample needed for comparison.
Ejection Patterns Depends On:
weapon design and condition
position held when fired
floor type - bouncing
obstacles i.e. walls