Related with basic understanding of firearms

1. Firearms

2. FIREARMS: OSCAR PISTORIUS
• February 14, 2013
–1:30am—neighbors of Oscar Pistorius,
Paralympic champion and Olympic runner,
call police for a noise disturbance
–Pistorius shoots his girlfriend Reeva
Steenkamp
–Acknowledges that he shot Steenkamp
four times, but said he mistook her for a
possible intruder
–Spends the night at the Boschkop police
station

3. FIREARMS: OSCAR
PISTORIUS

4. FIREARMS:
OSCAR
PISTORIUS

5. FIREARMS: OSCAR
PISTORIUS
• A case of premeditated murder is opened
against Pistorius
• February 19—Pistorius insists he did not plan
to kill Steenkamp and cries uncontrollably and
states the loved her
• February 22—Pistorius posts bail and the case
is postponed to June 4

6. FIREARMS: OSCAR
PISTORIUS
• March 3, 2014—Trial starts
–Pistorius is also charged with illegal
possession of ammunition and firing a gun
in a public space
• First witness (neighbor) testifies to hearing
“blood-curdling” screams before the sound of
gunshots on the night Pistorius killed
Steenkamp

7. FIREARMS: OSCAR PISTORIUS
• March 24—Whatsapp messages between
Pistorius and Steenkamp are read
– “I’m scared of you sometimes and how you
snap at me and how you will react to me”
• April 7—Pistorius takes the stand
– Begins with an apology “There hasn’t been a
moment since this tragedy happened that I
haven’t thought about your family”
• Pistorius is cross examined for 7 days
• Forced to look at Steenkamp’s head wound, re-
read Valentine’s Day cards Steenkamp sent him,
etc.

8. FIREARMS: OSCAR PISTORIUS
• September 11, 2014—Pistorius is found guilty
of culpable homicide. Found not guilty of
murder and granted bail until his sentencing

9. Firearms
• Forensic analysis is vital to solve a crime that
uses a gun
• In 2018, there were about 14,600 gun-related deaths in
the US (not including suicides)

10. A Quick History
• Almost every gun is based on the same simple
concept: You apply explosive pressure behind a
projectile to launch it down a barrel
• The earliest & simplest application of this idea
is the cannon
• The 1st handheld guns were essentially mini-
cannons; you loaded some gunpowder & a steel
ball & lit a fuse

11. A Quick History

12. A Quick History (cont.)
• War typically resulted in the need for improved
weapons technology
• In the late 1800s, the revolver quickly became
popular due to its size & quick loading
– It only had to be reloaded every 5-6 shots
instead of after each shot

13. A Quick History(cont.)
• Handguns reigned supreme for the past 200
years &, to this day, remain the most popular &
readily available firearm

14. Types of Firearms
• Handguns
– Pistols, semiautomatic handguns, machine
pistols, revolvers
• Long/Shoulder Guns
– Rifles, shotguns
• Mounted guns
– Large machine guns mounted on an aircraft,
tank, etc.

15. Ammunition
• Components:
– Cartridge case (container that holds all
components together)
– Primer (explosive chemical compound that
ignites the propellant when struck by a firing
pin)
– Propellant (often gunpowder; burns rapidly
and converts to an expanding gas)
– Projectile (bullet; object expelled from the
barrel)

16. Ammunition

17. Firearms Identification
• Firearms is often confused with the term
ballistics
• Ballistics is the study of a projectile in motion
• Identification of firearms is based upon this
basic idea: A harder object marks a softer one
& imparts/transfers its microscopic
irregularities to that object

18. Pulling the Trigger
• Pulling the trigger releases the firing pin…
• The firing pin strikes the primer…
• The primer ignites the gun powder…
• The powder generates gas that propels the
bullet forward through the barrel & ejects the
spent cartridge case
https://www.youtube.com/watch?v=TXliIJ_66FQ
https://www.youtube.com/watch?v=rJMXXuGhINE

19. Firearm Evidence
Individual:
• Striae
• Firing pin marks
• Breech marks
• Extractor marks
• Ejector marks
• Chamber marks
Class:
• Bullet type
• Bullet caliber
• Bullet weight
• Lands & grooves
• Rifiling
• Cartridge case
• Head stamp

20. Bullet Caliber
• Caliber is the diameter of the gun barrel
• Caliber is recorded 2 ways:
– Hundreths of an inch (.22 & .38)
– Millimeters (9mm)

21. Bullet Comparisons
• Each gun leaves distinct markings on a bullet
passing through it
• A gun barrel is made from a solid bar of steel that
has been holloed out
• The drill leaves microscopic marks on the barrel’s
inner surface
• Gun manufacturers also add spiral grooves to the
barrel. This is known as rifiling
• As a spinning bullet passes through the barrel, it
is marked by these grooves

23. Firearm Evidence
• Breech marks—left when the shell is forced
back against the breech of the gun
• Firing pin marks—impression left unique to the
gun’s firing pin on the back of the cartridge
• Head stamp—tells who manufactured the case
• Extractor & Ejector marks—extracting pin and
ejector leave marks on the shell casing when
throwing the spent shell from the chamber

24. Gunshot Residue (GSR)
• When a weapon is fired:
– Primer and propellant particles blow back
toward the shooter
– Combustion products, unburned propellant,
and particles of lead follow the bullet,
spreading out with distance

25. Contact GSW
• Since the barrel
contacts the
skin, the gases
released by the
fired round go
into the
subcutaneous
tissue & cause
the star-shaped
laceration Entrance wound

26. Abrasion Ring
• Formed when the force of the gases entering
below the skin blow the skin back against the
muzzle of the gun

27. Exit Wounds
• Exit wounds vary in size and shape because the
bullet can be deformed in its transit through the
body
• There may be no exit wound at all if the bullet’s
energy is absorbed by the tissue. Some bullets
are designed to deform so that all their energy
will be converted to tissue damage and not exit

28. Firearms Evidence Collection
• Make sure it is unloaded!!!!
• Revolvers
– Indicate location of fired & unfired ammunition
• Automatics
– Check magazine for number of rounds
– Fingerprint magazine
• Place ID tag on trigger guard
• Ammunition
– Package in pill box or envelope
– Wrap in tissue to protect