FORENSIC BALLISTICS😊

FORENSIC BALLISTICS

Ballistics

• Study of firearm & its effects.

• Calvin Goddard: Father of Ballistics

Types of Ballistics

• Internal Ballistics:
• Study of structure of firearms.
• Motion of projectile within the firearm.

• External Ballistics:
• Study of motion of firearm in air after being fired.

• Terminal Ballistics:
• Study of effects of the bullet in the target.
• Wound produced.

• Mnemonic: Ball was used as bullet earlier → Ballistics

Parts of a Firearm

1. Stock/handle.

2. Breech.

3. Barrel.

4. Muzzle: Outer end of the barrel.

Classification

• Based on the inner surface of the barrel.

• Visualized by helixometer.

Rifled gun:

• Inner surface of barrel has Rifling.
• Spiral grooves made in the inner surface.
• Using broach/hook cutter.
• Rifling spins the bullet, increasing stability.

• Projectile is Bullets.

Smooth-bored gun/shotgun:

• Inner surface of barrel is Smooth.

• Leads to dispersion of lead shots and poor precision.

• Projectile is Lead shots/pellets.

Choking

• Narrowing the terminal end of the barrel of smooth-bored shotguns.

• Purpose: ↓ dispersion.

Grades:

• Cylinder bore/unchoked: Maximum dispersion.

• Modified choke.

• Improved cylinder.

• Full choke: Least dispersion.

• Paradox gun:
• Smooth bored gun with terminal rifling.

• C () M () I () Full () choke

Internal diameter of firearms

• Rifled gun:
• Measured by Caliber.
• Measurement is between 2 diametrically opposite lands.
• 2 methods:
• Direct: Diameter measured directly.
• Indirect:
• No. of spherical lead balls made from 1 pound of lead
• that precisely fit the barrel
• Diameter of 18G > 24G

• Smooth-bored gun/shotgun:
• Measured by Gauge/bore.

Ammunition

Structure

• Shotgun cartridge:
• Has 3 compartments.
• Top compartment: Contains lead shots.
• Middle compartment:
• Contains wad.
• Travels around 2 meters.
• Produces minor bruises.
• Functions:
• Lubrication of the barrel.
• Separation: B/w gun powder & lead shots.
• Obturation
• Piston like action → additional push
• Base compartment:
• Contains gun powder.
• Also contains Primer/detonator/percussion cup.

Rifle bullet:

• Has bullet case.

• Wad: Absent
• Single bullet directly placed over gun powder

• Also contains Primer cup and Gun powder.

Types of Gunpowder

• Black gunpowder:
• Energy produced: Low (1gM 3-4 litres gas).
• Smoke: High.
• Components:
• Potassium nitrate (75%).
• Charcoal (15%).
• Sulphur (10%).
• Mnemonic: Preethi (dark complexion wearing powder) Can Sing.

• Semi-smokeless:
• Black gunpowder (80%) + smokeless gunpowder (20%).

• Smokeless gunpowder:
• Energy produced: High (1g 12-13 litres gas).
• Smoke: Low.
• Components:
1. Nitrocellulose.
2. Nitroglycerine.
3. Nitroguanidine.

Types of smokeless gunpowder:

• Single base: Nitrocellulose.
• Double base: Nitrocellulose + nitroglycerine.
• Triple base: Nitrocellulose + nitroguanidine + nitroglycerine.

Fineness of gunpowder

• FG < FFG < FFFG < FFFFG.

• ↑ fineness of gunpowder → ↑ ability to burn.

Primer

• Helps to BLAST the gunpowder.

• Mnemonic: Barry () Stephi () Auntye BLAST enn vilich → Lead () to 4 sin (tetrazine).
• Barium nitrate.
• Lead peroxide.
• Antimony sulphide.
• Styphnate (Lead).
• Tetrazine.

Discharges From a Gun

In order of emission from the gun

• Remember sequence

• Flame:
• Burns & charring of skin.
• Singeing of hair.

• Smoke:
• Blackening/smudging
• Can be wiped with a wet cloth

• Unburnt gun powder:
• Tattooing/peppering (Reddish brown abrasions).
• Can’t be wiped with a wet cloth.

• Bullet:
• Punctured wound.
• Grease collar/bullet wipe/dirt collar.
• Abrasion collar.

Grease collar/bullet wipe

• Mnemonic:
• Bullet () From () Some () Gun ()
• Theeyum Pokayum Podiyum

• Bullet entry wound → Grease collar → Abrasion collar → burning (flame) → blackening (smoke) → tattooing (unburnt gun powder)

• D/t deposition of grease from the outer surface of bullet onto entry wound margin.

• Most reliable Sign of entry wound.

Abrasion collar

• D/t gyroscopic action of bullet → margin of entry wound is abraded

• Shape gives information on trajectory of bullet.

Rat hole / Cookie cutter appearance

• Bullet injury

• Mid or Near range gunshot

Gun Ranges

Rifle Gun Ranges

Contact shot

• Gun in contact with skin:
• Tight contact: Recoil abrasion/muzzle impression.
• Tight contact on bony prominence (Skull/sternum):
• Burning, Blackening, Tattooing.
• All seen inside the track of wound.

• Close shot (within range of flame).
• Close friend

• Near shot (Outside flame, within smoke).
• Near smoke

• Intermediate shot (Outside smoke, within gunpowder).
• Into the gun

• Distant shot (Outside gunpowder range).
• Distant range

Wound Characteristics in Other Rifle Shots

• Burns Border Tells Entry

Characteristics	Close shot	Near shot	Intermediate shot	Distant shot
Burning	+	⛔	⛔	⛔
Blackening	+	+	⛔	⛔
Tattooing	+	+	+	⛔
Bullet wound, grease collar & abrasion collar	+	+	+	+

Short Gun Ranges

• Contact:



• Stellate or cruciate margin.
• Lead shots inside the track of wound as a single mass.
• Rifle gun and short gun similar → Can differentiate with the help of bullet
  

• Close (< 1m):





• All lead shots enter as a single mass.
• Burning, blackening, tattooing seen around the wound.

• Near (1 - 2m):



• Central single hole with lead shots as single mass.
• No other effects around wound.

• Intermediate (≥ 2m):



• Dispersion has started.
• Central hole with satellite holes.
• Satellite holes: Independent pellet holes seen around the wound.

• Distant:(4 m)



• Complete dispersion.
• Every pellet seen as independent hole.

Atypical dispersion

• Balling/welding of shots:
• Incomplete dispersion of lead shots
• D/t excessive grease/lubricant heat
• Distant range mimics intermediate shot

• Billiard ball ricochet effect:
• D/t erratic dispersion on hitting intermediate object
• Near shot resembles distant range

Determination of Entry & Exit Wound

• Note: Entry wound with everted margin is a Contact shot on bony prominence.

Bullet Fingerprinting & Atypical Bullets

Bullet fingerprinting

• Identifying gun from the bullet markings.

Markings on a gun

1. Primary marking/class characteristics:



• Marks produced on a bullet by rifling in the barrel.
• Give information about make/model of gun.

2. Secondary marking/fingerprint of a gun:



• Produced by irregularities of the barrel
• Individual characteristics: Vary from gun to gun
• Irregularities are caused by:
• Wear & tear.
• Manufacturing defect.
• Metallic fouling:
• Molten lead particles deposited on barrel,
• Produce additional markings on bullet.
• Mnemonic: Metal foul → bullet metal stayed in barrel

Note

• Handling of bullet:



• Rubber-tipped tweezers (Toothed forceps cause additional markings).
• Gloved hands.

Gunshot Residue (GSR) Test

• To find out if accused has used the gun.

• GSR collected using paraffin wax

• GSR test can be done by:
• Mnemonic: Firing HANDS.
• Flameless Atomic Absorption Spectrometry (FAAS).
• Harrison Gilroy test.
• Atomic Absorption spectrometry.
• Neutron activation analysis.
• Dermal Nitrate test.
• SEM-EDXA
• Specific test
• Scanning electron microscope - energy dispersive Xray Spectroscopy
• Mnemonic: Harri () Sem Exam () nte thalennu Nightil (Nitrate) New Activities (Neutron activation) Absorb (Atomic absorption) chyeyan nokki → exam potti → gun vach fire cheyth marich

Atypical Bullets

• Tandem/Piggy-back:
• 2 bullets coming out back to back.

• Semi-jacketed/dum-dum:
• Tip of lead core is exposed to outside,
• Mushrooms on entering skin & cause greater damage.

• Yawning: Irregular bullet path.

• Tumbling: Bullet rotates end to end.

• Frangible: Fragments on impact.

• Souvenir:
• Retained bullet inside the body.
• Chronic complication: Plumbism.

• Ricochet:



• Bullet stops spinning on hitting intermediate surface
• No abrasion collar.
• No effects of flame, smoke, or gunpowder on the entry wound.

• Tracer:
• Luminous metal at the base → Glows → Can trace the path of the bullet.

• Kennedy phenomenon:
• Iatrogenic alteration of gunshot wound,
• Difficulty in range determination.

• Rayalasima phenomenon
• Stab → Bullet

Gunshot Wound on the Skull

Bevelling

• Differentiated entry wound from exit wound.

• Bevelling in inner table: Entry wound.

• Bevelling in outer table: Exit wound.