Topic 5 - shooting scene investigation Flashcards
what is a shooting RECONSTRUCTION?
the process of utilising information derived
from physical evidence at the scene, analyses of physical evidence, and inferences drawn from such analyses to test various theories of the occurrence of prior events.
what is a shooting RE-ENACTMENT?
a demonstration of a previously existing
reconstruction based on conjecture rather than scientific principle.
why would you do a shooting reconstruction?
- To answer who, what, when, where, how and why?
- To understand the component factors of a shooting – trajectories, distances, cartridge case ejections, ricochets etc.
- To provide a range of possible positions for shooter and victim and thus ‘paint the picture’ of prior events.
- To corroborate or dismiss claims made about a given shooting for the courts.
what are the four main outcomes when a bullet impacts a surface?
- The bullet remains intact and passes through causing identifiable entry and exit holes.
- 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 of the fragments are either retained or pass through.
- The bullet bounces off either intact or fragmented.
what are some general indicators of firearm use at a scene?
bullet, cartridges and fragments of bullets
Gunshot residue (GSR)
size and shape of hole
evidence of high energy penetration and damage highly local to the hole, which depends on the material
what does a bullet hole in metal look like?
- Normally quite easy to distinguish and
usually neat on the entry side of the hole - Exit side will look like a ‘truncated’ funnel. There may be a wipe ring on the inside of the funnel.
- The length of the “funnel” depends upon:
Caliber & Projectile velocity.
Physical characteristics of the metal.
Bullet construction.
Will just be a dent if the plate is thick.
Paint or surface mark if the plate is very thick.
what does a bullet hole in wood look like?
in wood and other frangible materials the entry side of the whole is usually neat, but cratered and splintered on the exit side and the exit side distributes a lot of debris.
- Low velocity, large caliber will cause significant
splintering on the exit side. - Small caliber, high velocity makes a neater hole.
Soft wood tends to splinter less than hard
wood.
* Plywood will delaminate with large sections of the
back layer being torn away.
There may be a wipe ring towards the entry
side.
what are the effects of bullet holes on glass?
- Dependent upon the type of glass, forensic information can be extracted from the impacts.
- Order of impact - radiating cracks will
not propagate across an existing fault. - High velocity bullets tend to leave
small neat holes with little fracturing. - Low velocity are the opposite which leave a lot of fracturing.
what are the effects of bullet holes on fabrics?
- If aligned with a wound, you can follow the bullet path into the body from the clothing.
- GSR if a close range shot.
- May get a bullet wipe ring too at all ranges.
- For synthetic fabrics: Microscopic examination
at the edge of the hole will show evidence of
individual fibres melting, resulting from the
frictional heating caused by the bullet’s transit. - Natural fabrics: Microscopic examination will
reveal fibres with shredded and frayed ends around the hole.
what is evidence of the firearm user?
flash burns on the target including Gunshot residue on the skin.
- Burns to fabrics and flammable surfaces.
- Imprints and impressions.
- This might include ricochet damage.
- Bullet/fragment wounds.
- This might also include wounds from debris launched by the bullet impacting a surface.
- Hearing damage.
what is “slide bite”?
this is a common injury with inexperienced firearm users - it is a result from mishandling the weapons.
slide bite 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.
what is “scope bite”?
- All telescopic sights are designed with a set “eye relief”.
- This is the optimal distance at which the view is in focus.
- This is designed to allow for recoil.
- Inexperienced users do not know this.
- This leaves a characteristic crescent-shaped contusion on the forehead or nose of the shooter.
what is “hammer bite”?
this is similar to slide bite but because this handgun has a different mechanism (a hammer that is external) - it should be noted it makes a different mark compared to slide bite, this mark is smaller and less noticeable.
- SLPs with an external hammer can pinch the web between thumb and fingers.
- Different from slide bite in that a mark may be present that can be matched specifically to the hammer.
- There may also be DNA left on the firearm hammer chequering.
what are “recoil marks”?
- Recoil marks left on the body will vary and are dependant upon type of weapon used and the experience of the user.
- Rifles and shotguns will imprint on the shoulder and upper arm through clothing (if present).
- Handguns may imprint chequering and grip patterns on the palm and web of the hand.
- These imprints may be short-lived indents, or long-term bruising.
what are string lines and when are they used?
string lines are used when reconstructing trajectories
they are cheap
they are easy for the jury to understand in court
main drawback is they requiring being anchored to keep them at high tension
the line passes through the centre of the bullet hole
they show the extended bullet hole (past the exit wound trajectory
different colours used for different shots.
