Firearms

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

FireArms: Oscar Pistorius

Firearms: Oscar Pistorius

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

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

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.

Firearms: Oscar Pistorius September 11, 2014—Pistorius is found guilty of culpable homicide. Found not guilty of murder and granted bail until his sentencing

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) The vast majority of U.S. homicides involve guns. And they are more powerful than ever. Lansing State Journal, July 2007

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

A Quick History

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

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

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

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)

Ammunition

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

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

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

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

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

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

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

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

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

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

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