Ballistics & Firearm Identification Handguns

 2 Primary Types of Handguns  Pistol  Revolver Pistol  Handgun with single barrel and chamber.

 Pistol fires chambered round, extracts and ejects an empty casing and loads a new round into chamber with each trigger pull.

Revolver  Handgun with a cylinder that has multiple chambers.  When trigger is pulled, cylinder rotates around a central pin to align the next chamber with the firing pin.  Single barrel fires one round per trigger pull.

Single Action vs Double Action

 The hammer on a single-action revolver must be cocked manually.  A double action revolver can be fired with one pull of the trigger, which cocks and drops the hammer with the pull. 4 Primary Parts of a Pistol  Frame  Barrel  Slide  Magazine Projectiles

 Bullets  Shotgun Shells  Shotgun Slugs

Shotguns

 Generally do not have a rifled barrel. Projectile does not spin as it travels through.  The shotgun shell contains the projectile.  Shotguns generally referred to by a gauge.  Gauge is the measurement of the barrel’s inside diameter. (Smaller the gauge, larger the diameter).

Types of Shotguns

 Generally, three types:  Semiautomatic, pump action, break open

Forensic Ballistics

 In forensic science, the study of ballistics is the study of motion, dynamics, angular movement, and the effects of projectiles. Firearms Identification

 Firearm identification deals with the comparison analysis of projectiles and cartridge cases found at crime scenes to submitted suspect firearms.  The basis of firearm identification is in the microscopic individual characteristics caused during the manufacturing process. Additional imperfections may arise from use, abuse, wear, and corrosion. These imperfections caused by manufacture or over time are what make the tool surfaces in firearms unique.  Firearm examiners can also analyze for distance determinations, operability of firearms, and serial number restorations. Firearm Image Database

NIBIN (National Integrated Ballistics Information Network)

Ballistics Comparison

Identifying Firearms

 Serial Number  Manufacturer  Type of Firearm  Loaded/Unloaded/Chambered  Any other descriptive characteristics (sawed off barrel, damage to weapon) 6 Ways to Link Firearms to Scenes

① Striations in fired bullet ② Gunpowder residue leaves patterns ③ Trajectory, ricochet, bullet holes ④ Hidden fingerprints ⑤ Firing pin impressions ⑥ Bullet damage to tissue

(Forensic Outreach, 2015) 1) Striations in Fired Bullet  Comparison microscope used to compare bullet/projectile from scene to bullet/projectile fired from suspected firearm.  If no suspected firearm, striations can identify the type and model of firearm used. 2) Gunpowder Residue Patterns

 When a gun is fired, not just the bullet exits. Gunpowder particles expectorate, create a pattern on an object closest to the barrel.

3) Trajectory, Ricochet, Bullet Holes

 Trajectory of the shot provides a picture of the scene.

4) Hidden Fingerprints

 Someone handling a firearm will touch more than just the stock and trigger. 5) Firing Pin Impressions

 Firing pins leave individual marks on the primer at the bottom of each bullet.  Alignment, size of impression, and age of the firearm contribute to the hard mark (pin) left on the soft mark (primer). 6) Bullet Damage to Tissue

 Wounds can provide an incredible amount of information about sequence of hits, distance, velocity, bullet type, caliber, and more – whether a bullet fragment is recovered or not.  Bevelling around an entrance wound holds clues, fracture lines in dense bone such as skulls can identify distance, velocity and direction of fire.  Grazing bullets leave skin tags – little flags of ragged skin that are pulled up and torn as a projectile passes by at high speed

Firearm Identification