Forensic Ballistics: Study of Firearms and Projectile Trajectories

Firearm(Ballistics)

Father of ballistics- Calvin Goddard. Ballistics is the study of projectile motion, which refers to anything that comes out of firearms. Examples include bullets and lead shots. 

Firearm- weapon; Ammunition- bullet, explosive material; Problem- wound. All these three things are called forensic ballistics. 

Classification of Ballistics

• Proximal(internal) Ballistic:  Study of the projectile in firearm weapon. 

Intermediate(exterior) Ballistic: Study of the motion of projectile gun barrel till the time it hits the target.

• Terminal Ballistics: Penetrate the target.
• Wound Ballistic: Penetrate in living tissue. 

Classification of Firearm

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Advantages of Rifling in Rifled Firearms

• It has spin and rotation of the bullets. 
• Increases accuracy and range (kinetic energy is more, therefore range is more).
• It checks the wobbling effect.
• It causes gyroscopic stability. 
• Enhances wounding power. 

Caliber or Gauge: it is used for rifled weapons. 

Bore or Gauge: It is used for smooth bore weapons. 

The number of balls/pellets of equal size/weight are made up of 1 pound lead(454gm)

12 bore = 12 balls

Bore decides the size of the pellets

Helixometer: It is an instrument to examine the inner surface of a barrel. 

How to Increase the Range of Shot- Gun

Different ranges of Firearm

• Shotgun:  50 to 60 yards
• Revolver: 200 yards
• Pistol: 400 yards
• Military Rifle: 1000 to 3000 yards
• Airgun: 40 yards. The mechanism is air compression. Absence of tattooing, blackening, and singeing. 

Paradox gun: It is a mixed gun. It has features of both rifle and shotgun. It is a shotgun in which a part of the barrel towards the muzzle is rifled. 

Choking

The muzzle end of a shotgun is constricted to

•  Lessen the rate of speed of the shot. 
•  Increase the velocity of pellets. 

Different Types of Choking 

• Unchoked or cylindrical base: its range is 25 yards. 
• Improved cylindrical choke: its range is 30 yards. 
• Modified cylindrical choke: its range is 35 yards. 
• Full choke: its range is 40 yards.

Cartridge: Loaded within the firearm

• Primer: which ignites
• Propellent: Gunpowder
• Projectile: In rifle, it is bullets, and in the smooth bore, it is pellets.

The Rifle Cartridge 

• On the base, we have a primer cup. 
• In a rifled firearm, we have a bullet case composed of Brass( copper + Zinc)
• A bullet made of lead. 

Cartridge of Smooth Bore Firearm

• Primer cap/ detonator cap/ percussion cap
• Gun powder
• Cardboard disc as known as Wad. 
• Lead shots. 

Wad Function 

• It separates projectiles from propellants. 
• It seals air. 
• It acts like a piston and lubricant. 

Lead Shot: it is pellet/ lead balls. 

• Soft: composed of lead
• Hard: composed of Lead and Antimony 
• Steel: composed of steel

Size: It varies from Dust shot, Birdshot, and Buckshot. 

Primer Composition

• B- Barium Nitrate 
• L- Lead peroxide
• A- Antimony 
• S- Styphnate/ Antimony Sulphide
• T- Tetrazine

The Function of Primer

• First, it burns, then detonates(explodes), and then ignites the gunpowder. 

Gun Powder: it is of 3 types. 

1. Black (POCSO)

• PO: Potassium Nitrate (75%)
• C: Charcoal (15%)
• SO: Sulphur (10%)
• 1gm produces 3000-4000 cc of gas. 
• Produce more smoke.
• Have less power.

2. Smokeless

• Single base: it contains Nitrocellulose. 
• Double base: it contains Nitrocellulose and Nitro-glycerine 
• Triple base: it contains Nitrocellulose and Nitro-glycerine, Nitroguanidine
• 1 gm produces 12000-13000 cc of gas.
• Produce less smoke.
• Have high power.

3. Semi Smokeless Gunpowder contains 80% Black and 20% Smokeless gunpowder. 

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Gunshot Residue Test (GSR)

It is composed of primer and lead. 

• H-Harrison and Gilroy test. It can detect Antimony, Barium, and Lead.
• A- Atomic absorption Spectrometry. It can detect Antimony, Barium, Copper, and Lead
• N- Neutron activation analysis.
• D- Dermal nitrate test, also known as Paraffin test.
• S- Scanning electron microscopy energy dispersive X-ray analysis(SEM-EDXA). It is the most specific test. 

The Sequence in Firing

The trigger is pulled. Once you pull the trigger, the hammer will rise. It will move upwards and release, hitting the firing pin, and then it will move forward. Then the primer burns, and flames produce gunpowder. When gunpowder ignites, gas or smoke in a small compartment is produced, and the projectile can come out. 

Bullets 

• Damage depends on the velocity. 
• Large round bullets have greater damage. 
• Should be picked by hand from the crime scene.

Types of Bullets

•  Souvenir bullet: also known as sleeping bullet. It is a retained bullet in the body or skin. Surrounding the bullet there will be fibrosis; it is composed of lead. So, it will cause lead poisoning, which is known as Plumbism. 
• Frangible: It divides into multiple components. Composed of Iron and copper. 
• Tumbling: Rotates end-to-end. 
• Duplex: Two bullets in a cartridge. 
• Tracer: Can be traced in your pathway. Because the base is composed of illuminating subjects. 
• Incendiary: Contains phosphorus. It catches fire. 
• Yawning: Slow and irregular bullet. 
• Tandem: If two bullets are coming out, it is called tandem also known as piggyback bullets. 
• Plastic or Baton Bullet: It is composed of polyvinyl chloride and used in riot control. 
• Piston bullet: Curare, resin. Any type of poison in a bullet is known as a poison bullet. 

Ricochet Bullet

If a bullet is deflected from any object, it goes into your body. 

• The critical Ricochet angle is 30 degrees. 
• Spin and rotation lost, so no abrasion collar.
• Burning, blackening, and tattooing all are absent. 
• Round nose tip bullet - Round Tip
• Sharp nose bullet- Sharp pointed Tip
• Fully jacketed bullet- Copper jacket 
• Semi-jacketed bullet- Nose is not jacketed, expanded inside tissues. 
• It can be of two types:
  • Dum-Dum Bullets
  • Hollow Pointed Bullets

This causes more external damage due to expansion. 

Kennedy Phenomenon

• Surgical alteration of gunshot wounds. If it dies during the post-mortem, it is difficult to identify the entry, exit wounds, and range difficulty. 

Rayalaseema Phenomenon

• Bullets are implanted in stab wounds to mislead the investigation. 

Discharge from Gun- Effects

• Flame: Causes burning of hair, charring, singeing 
• Smoke: Smoke is deposited surrounding the skin. This phenomenon is known as blackening and smudging. 
• Unbound Gun Powder: This is impregnated in the skin and known as tattooing, peppering, and stippling. 
• Projectiles from Shotgun: Lead shot (wad), Rifle(bullet). 

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