Gunshot Wounds

Question 1

Types of guns

Answer 1

Rifled weapon fire single bullet
- handguns
- rifles - grooved spiralled long barrel
Smooth bore weapons fire multiple lead pellets
- shotgun

Question 2

Ballistics motion of projectiles

Answer 2

Interior ballistics
- travel within weapon
Exterior ballistics 
- travel in air
Terminal ballistics 
- penetration of solids
Wound ballistics
- penetration of tissues

Question 3

Types of interior ballisitcs

Answer 3

Rifling marks on bullet
- class characteristics - make/model
- individual characteristics - unique to gun
Cartridge case - extractor
Primer cap - firing pin
Fingerprints

Question 4

Effects of kinetic energy in bullets

Answer 4

Large velocity gives high energy on impact
KE = 1/2 mass of bullet x velocity^2
Double mass of bullet -> double energy
Double velocity -> quadrupled energy
Wounding effect due to transfer from bullet to tissues
- miss = no energy transferred
- exit = not all energy transferred
- no exit = all energy transferred

Question 5

Types of small firearms

Answer 5

Shotguns - smooth bore
Handguns
Rifles
Submachine guns
Machine guns

Question 6

Rifling marks

Answer 6

Lands and grooves inside barrel give specific characteristics
Class characteristic of weapon
- number of lands and grooves
- width
- depth
- degree of twist
- direction of twist
Individual characteristics of weapon
- imperfections on lands and grooves due to use

Question 7

Types of handguns

Answer 7

Single shot pistols
Derringers
Revolvers
Auto-loading pistols

Question 8

Features of revolvers

Answer 8

Rifled barrel
Fired from hand
Revolving cylinder
Several chambers
Types
- solid frame 
- swingout - chamber spins outside ways
- breaktop - load from behind

Question 9

Features of auto-loading pistols

Answer 9

Rifled barrel
Fired from hand
Removeable magazine stores cartridges - sits in handle
Mechanism for autoloading - fires 10-15 shots one after each other

Question 10

Features of rifles

Answer 10

Rifled barrel
Fired from shoulder
Single projectile
Types
- single shot
- bolt action
- lever action
- pump action
- autoloading

Question 11

Features of sub-machine guns

Answer 11

Rifled barrel
Fired from shoulder or hip
Fires pistol ammunition
Capable of fully automatic fire

Question 12

Features of machine guns

Answer 12

Rifled barrel
Fired by individual or crew
Fires rifle ammunition
Capable of fully automatic fire

Question 13

Parts of small arms ammunition

Answer 13

Bullet
Propellant
Primer
Cartridge case

Question 14

Handgun ammunition

Answer 14

A range of calibre - .22 to .5 inch
Blanks has case, propellant with a plastic cap but no bullet
Different tip types

Question 15

Features of small arms ammunition

Answer 15

Cartridge case
- composed of brass cylinder
- filled by propellant
- expands to fill chamber on discharge
Primer
- lead, barium and antimony compounds
- shock-sensitive chemical compound explodes on impact by firing pin
- flame secondarily ignites propellant
- 2 types - centrefire (firing pin strikes centre) and rimfire (firing pin strikes anywhere on base)
Propellant
- smokeless powder - nitrocellulose +/- nitro-glycerine
- burns to produce large volume of gas under pressure
- forces projectile down and out of barrel
- formulations - discs, flakes, cylinders, balls or flattened balls

Question 16

Features of lead bullets

Answer 16

Usually lead but can be alloyed with tin/antimony
May have thin copper gilding
Used in revolvers and .22 rimfire cartridges
Types
- round nose
- wadcutter
- hollow point - mushroom and stay within animal preventing secondary damage and injury

Question 17

Features of jacketed bullets

Answer 17

Lead or steel core
Encased in jacket of CuZn, CuNi or Al
Used in auto-loading pistols and HV rifles
Types
- full metal jacket - HV military rifle
- partial metal jacket - hunting and autoload pistol
- semi-jacketed hollow soft/point - hunting
- silvertip - all

Question 18

Wounding mechanisms from bullets

Answer 18

Direct laceration - permanent cavity
Temporary cavity > 800m/s
- opens in wake of bullet and collapse on exit
- wide zone of haemorrhage around wound tack
- dense inelastic organs (liver) may rupture
Shockwaves may rupture gas-filled organs (bowel, bladder)
Secondary projectiles - bone fractures cause injury
Discharge gases at contact range

Question 19

Gunshot signs range

Answer 19

Flame - 5cm
Smoke - 15cm - billows out so wider radius
Tattooing - 50cm - burnt propellant marks skin

Question 20

Features of entry wounds

Answer 20

Abrasion and stretching of skin from contact

Chips away bone as exits cause conical appearance

Question 21

Features of exit wounds

Answer 21

Smaller hall on entry side and larger on exit side - conical shape
Exit defect in skin larger than bullet due to skin being stretched

Question 22

Skin surface characteristics of gunshot wound

Answer 22

Muzzle imprint
Hot gases - singeing
Soot - smudging
Propellant - tattooing
Bullet
- skin defect
- abrasion of margin
- microtears
- bullet wipe

Question 23

Features of contact range wound

Answer 23

Soot and propellant seared into margins
Loose contact - sideways escape of soot-laden gas
Angled contact - eccentric soot stain

Question 24

Features of near contact range wound

Answer 24

Few cm
Soot and propellant seared into margins
No tattooing
Peripheral ring of soot staining
- soot reached 20-30cm
- can be wiped off

Question 25

Features of intermediate range wound

Answer 25

Few cm to 1m - arms reach
Powder tattooing
- unburnt or partially burnt propellant grains
- individual reddish-brown punctate abrasions
- vital reaction - rim of bruising
- eccentric pattern if angled entry
- spread depends on powder, range and barrel
- reaches up to 30-40 cm

Question 26

Features of distant range wound

Answer 26

Beyond 1m - beyond arm's length
No flame effect
No soot effect
No propellant tattooing
Bullet is on its own
Skin defect with marginal abrasion
- circular if impact at right angle
- elliptical if impacting at another angle

Question 27

Entry vs exit wounds

Answer 27

Entry
- circular defect
- diameter < bullet
- abraded margin
- soot 
- propellant
Exit
- irregular shape
- diameter > bullet
- no abrasion
- near exit

Question 28

Features of gunshot residues

Answer 28

Spheroidal particles of barium, lead and antimony compounds from primer
- condensation and solidification of molten and vaporised primer and bullet materials
Newer lead-free ammunition
Deposited on radial side of firing hand
Cotton tipped swab moistened with HCl or HNO3
Sent for forensic scientific analysis

Question 29

Formation of gunshot residue

Answer 29

Hammer within firearm strikes outside of priming cap crushing explosive
Shock-sensitive chemical compound explodes igniting secondary charge of gunpowder
Temperatures exceed 2000°C
Unburnt powder and vaporised metallic components from priming cap remain within recently formed gasses
Increase in pressure causes ejection of bullet from casing and barrel
Spherical particles formed are composed of elements present in the primer therefore making gunshot residue unique

Question 30

Shotgun discharge range

Answer 30

Flame - 15cm
Smoke - 38cm
Powder tattooing - 60cm
Wad - 1m
Satellite holes - 2m
Uniform peppering - 10m

Question 31

Features of shotguns

Answer 31

Smooth barrel
Fired from shoulder
Fires multiple pellets
Types
- single shot
- double barrel
- over and under
- bolt
- lever 
- pump
- autoloading

Question 32

Shotgun gauge

Answer 32

Number of balls of lead exactly fitting the barrel diameter which make up 1lb in weight

• .410 is 10.2mm internal diameter
• 20 gauge is 15mm
• 12 gauge is 18.2mm
• 10 gauge is 21 mm

Question 33

Features of choke of barrel

Answer 33

Taper towards muzzle keeping shots more closely clustered
Measured as % shot striking within 30” target circle at range of 40 yd
- cylinder = 30%
- improved cylinder = 40%
- modified choke = 50%
- full choke = 60%

Question 34

Parts of shotgun ammunition

Answer 34

Crimped plastic tube
Shot
Wad - plastic
Powder
Primer 
Brass head plate

Question 35

Shotgun power piston

Answer 35

Plastic spring shaped wad
12g, 16g and 20g have 4 petals
.410 has 3 petals
Pushes shot out of barrel 
Contributes to wound
- < 1f not yet opened
- 1-3 ft abrasions from petals
- > 3 ft folded back
- 8-10ft strikes alongside entry
Indicates manufacturer and gauge

Question 36

Features of contact shotgun wound to head

Answer 36

Very mutilating
- gas
- energy of shot
Scalp laceration
Skull fracture
Brain may be blown out
Most pellets and wad may exit

Question 37

Features of contact shotgun wound to torso

Answer 37

Circular entry = muzzle diameter
Muzzle imprint
Soot smudging
Burning or melting of clothes
Cherry pink wound margin - CO

Question 38

Features of distant range shotgun wound

Answer 38

Small circular defect < 2'
No tattooing > 3'
Scalloped margins by 3'
Satellite holes (fliers) by 4'
Cuff of satellite holes by 6'
Beyond 10' entry depends on 
- range
- length and choke of barrel
- ammunition
Test firing required

Question 39

Features of gunshot suicide

Answer 39

Rare in females
Contact wound -> presumption of suicide
HV blood splatter on steadying hand
GS residues on firing hand
Evidence of test firing
Sites of election 
- head = 80%
- chest = 15%
- abdomen = 5%

Question 40

Important points in gunshot cases

Answer 40

Beware of artefacts and loss of evident
Take X-rays
Examine clothing for burns, tattooing and gunshot residue
Examine hands
- soot
- blood
- residues
Recover projectiles
- bullet, pellets
- propellant, wadding

Question 41

Problems with gunshot cases

Answer 41

Shored or partial exit wounds
Bullet ricochet out of and within body
Separation of bullet jacket and core
Projectiles may embolise or move
Plastic wad and AI jacket invisible on x-ray
X-ray may magnify projectiles
Snooker ball effect of pellets