Gun Shot Wounds Flashcards
What type of projectile does a smooth bore weapon fire
Multiple lead pellets
Includes shotguns
What is ballistics
The study of the motion of projectiles
What type of projectile does a rifled weapon fire
Single bullets
Includes handguns and rifles
What are interior ballistics
The study of the travel of projectile within the weapon
Includes rifling marks, cartridge case marks from extractor, primer cap marks from firing pin and fingerprints on bullet from loading
Can help identify the weapon a bullet has come from
What are exterior ballistics
The study of the travel of the projectile through the air
What are terminal ballistics
The study of the penetration of solids by a projectile
What are wound ballistics
The study of the penetration of tissues by a projectile
What types of rifling marks might you find on a bullet
Class characteristics - scratches which indicate the make/model of weapon
Individual characteristics which are unique to gun - irregularities appear with use
How do you calculate the kinetic energy of a bullet
KE = ½ Mass of bullet x Velocity2
Greater the mass of bullet and the greater the velocity the greater the energy (2x and 4x more respectively)
What causes the wounding effect to tissues in a gunshot
Caused by the transfer of energy from bullet to the tissues
Bullets are so harmful due to the speed at which they travel - high energy
If the bullet exits the body all of it’s energy has been transferred - true or false
False
Not all energy will have been transferred (still has energy to travel out of body)
A bullet that does not exit will have transferred all it’s energy
Which guns are considered ‘small arms’
Shotguns (smooth bore not rifled) Handguns Rifles Submachine guns Machine guns
What causes rifling marks on a bullet
Spiraled lands and grooves on the internal surface of the barrel Leads to lines/scratches on the bullet Can be used to identify class of weapon and even individual weapon
How can you identify the class/model of weapon from the rifling marks
You analyse the: Number of lands & grooves Width Depth Degree of twist Direction of twist
Should match a specific make/model
How can you identify the individual weapon from the rifling marks
Imperfections in the lands/grooves will leave unique rifling marks that can be matched to the weapon
Imperfections caused by firing/use - can change over time with use
Which guns can be classified as handguns
Single shot pistols
Derringers
Revolvers
Auto-loading pistols - like glocks
What are the main features of revolvers
Rifled barrel Fired from hand Revolving cylinder - spins to load bullets until they run out Several chambers Usually contain around 6 bullets
What are the main types of revolvers
Solid frame - hard to load
Swingout - chamber comes out at side
Breaktop - chamber opens on top
What are the main features of auto-loading pistols
Rifled barrel
Fired from hand - glocks like on TV
Removable magazine stores cartridges - usually in the handle
Mechanism for autoloading - will fire until magazine is empty
Press trigger each time to fire - not automatic fire
What are the main features of rifles
Rifled barrel
Fired from shoulder
Single projectile
What are the main types of rifles
Single shot Bolt action Lever action Pump action Auto loading
What are the main features of sub machine guns
Rifled barrel
Fired from shoulder or hip
Fires pistol ammunition - i.e. not lead bearing
Capable of fully automatic fire
What are the main features of machine guns
Rifled barrel Fired by individual or crew Mounted military weapons Fires rifle ammunition - larger ammo Capable of fully automatic fire
What makes up the ammunition required for small arms
Bullet at front
Propellant
Primer
Cartridge case around all
Describe the structure of a small arms ammunition cartridge case
Composed of a brass cylinder filled with propellent (e.g. gunpowder)
This expands to fill the chamber with gas when fired
Describe the composition of a primer in small arms ammunition
It is a shock-sensitive chemical compound which explodes when impacted by the firing pin
Made up of lead, barium & antimony compounds
What are the 2 main types of primer in small arms ammunition
Centrefire
Rimfire
What is used in small arms ammunition as propellent
Smokeless powder made of nitrocellulose +/- nitroglycerine
Can be in the form of discs, flakes, cylinder, balls or flattened balls
How does the propellent work in small arms ammunition
It burns to produce large volume of gas under pressure
Ignited by the primer explosion
This pressure forces projectile(s) down & out barrel
List the main types of lead bullets
Round nose
Wadcutter
Hollow point
Describe the structure of a lead bullet
Made of lead, alloyed with tin &/or antimony
May have thin copper gilding (thin coating)
Lead bullets are used in which types of gun
Used in revolvers and .22 rimfire cartridges
Handguns and rifles
List the main types of jacketed bullets
Full metal jacket (HV military rifle)
Partial metal jacket (hunting & auto-load pistol)
Semi-jacketed hollow soft/point (hunting)
Silvertip (Al)
Jacketed bullets are used in which types of gun
Used in auto-loading pistols (glocks) and high velocity rifles
Describe the structure of jacketed bullets
Have a lead or steel core
Encased in a jacket of CuZn, CuNi or Al
Jacket prevents them from fragmenting
List the wounding mechanism of a bullet
Direct laceration (permanent cavity)
Temporary cavity
This either causes a wide haemorrhage zone or rupture of a dense organ like the liver
Shockwaves may rupture gas-filled organ
Secondary projectiles (e.g. bone)
Discharge gases at contact range will also cause damage
How far does the flame reach after a gun is fired
Around 3 inches
Can leave burn/singe marks at entry wound if within range
How far does the smoke reach after a gun is fired
Around 6 inches
Will leave soot deposition at entry wound if within range
Describe the formation of the temporary cavity in a gunshot wound
The huge pressure of the bullet causes a cavity to form behind the bullet
This can be up to 30-40x greater in diameter than the bullet
It only lasts milliseconds and then collapses in a pulsatile fashion
This pulsing causes lots of haemorrhage
What are the effects of the temporary cavity in a gunshot wound
Can cause a wide zone of haemorrhage around the permanent cavity or rupture dense, inelastic organs like the liver
What features may you find on the skin after a shooting
Muzzle imprint - contact Singeing due to hot gases - close range Smudging of soot - within 6 inches Tattooing due to the propellent - scattered abrasions Skin defect from bullet Abrasions on the margins Microtears in HV shootings Bullet wipe
What is powder tattooing
Skin injury caused by unburnt or partially burnt propellant grains
Forms individual reddish-brown punctate abrasions where grains hit
May or may not have rim of bruising (vital reaction)
What determines the spread of tattooing from a gunshot
Depends on powder, range, barrel
Pattern also depends on angle of entry - eccentric if angled
What is considered a near contact range
Within a few centimeters of target but less than intermediate
List the features of a contact range gunshot wound
Singeing of the entry wound from flame
Soot and propellant seared into margins
If there was loose contact then soot-laden gas will escape sideways
If the contact was angled then there will be an eccentric soot stain
List the features of a near contact range gunshot wound
Soot and propellant still seared into margins of wound
No tattooing - too close
Peripheral ring of soot staining - can be wiped off
Soot reaches 20-30 cm
What is considered an intermediate range shooting
Few cm to 1 m
Basically within arm’s reach
May still be suicide
What are the features of an intermediate range shooting
Powder tattooing - small, individual abrasions from the propellent
This cannot be wiped off like the soot
May have some associated bruising
What is considered a distant range shooting
Beyond 1m
Beyond arms length
What are the features of an distance range shooting
No flame or soot effect and no tattooing as too far away
Bullet is on its own which causes skin defect (hole) with marginal abrasion
Hard to estimate distance at this point
How does angle affect shape of entry wound
Circular if impacting at right angle
Elliptical if impacting at another angle
List the features of a bullet entry wound
Circular defect
Diameter is less than the bullet due to stretching of skin (will shrink back)
Abraded margin
May have soot or propellant in/around wound if close range
List the features of a bullet exit wound
Irregular shape Diameter is greater than the bullet and larger than the entry wound No abrasion (unless shored)
Where is gunshot residue found on the hand
Deposited on radial side of firing hand
How do you sample for GSR
Cotton tipped swab moistened with HCl
or HNO3 (or tape)
Put it through mass spec
This picks up the residue and tells you if they have fired a gun recently
What is GSR composed of
Spheroidal particles of barium, lead & antimony compounds from primer
Caused by condensation and solidification of molten and vaporized primer and bullet materials
How is gunshot residue forms
The firing pin strikes the primer which causes it to explode and ignited the gunpowder
Some unburnt gunpowder and vaporized components from the primer are found in the resulting gas
The gas causes a rise in pressure which ejects the bullet
The vapors quickly condense into spherical particles which can be deposited on the shooter
These particles are composed of one, two or three of the primer elements and it is these particles together with their morphology that make GSR unique - can be analyzed and matched
How are ballistics tests carried out
The gun is fired into a water tank
The bullet is retrieved and can be analysed for rifling marks etc.
Firing pin can leave a mark on the base plate of the cartridge which can be identified
Military weapons are designed to have their projectiles fragment - true or false
False
They are designed to not fragment so that they keep going whilst injuring as many as possible
They will exit the body
What is meant by fully automatic fire
As long as trigger as pressed the gun will continuously fire until it runs out
Where would you typically find the magazine of a gun
Usually found in the handle
How do guns autoload
Once fired the gun ejects the spent cartridge and loads a new one
On a Glock the top slides back and forth to load and eject cartridge
What are hollow point and soft point bullets designed to do
They are designed to mushroom on impact so that they stay in the target
Shouldn’t exit the body
Designed for hunting
What are jacketed bullets designed to do
They are designed not fragment on impact
This allows you to hit more targets - designed for military use
Which type of ammunition is larger - handgun or rifle
Rifle ammunition is much larger volume wise, bullet is same size
It contains more propellent so travels further
Why does rifle ammunition travel further
Contains more propellent (larger ammunition)
This allows the bullet to travel faster and further
The longer barrel allows for accuracy
What causes abrasion at the entry wound
Imprint abrasion at point of contact due to compression by nose of bullet
It compresses and stretches the skin before breaking it
Skin then folds inwards
What distance does the WAD travel after a shotgun discharge
Around 1m or 3ft
Can be cardboard or plastic
Satellite holes would occur at what distance after a shotgun discharge
Around 2m
Centre wound with a few smaller satellite holes as the pellets start to spread out
Uniform peppering would occur at what distance after a shotgun discharge
Around 10m
Pellets can spread out and cause several wounds
Likely no central hole
List the main types of shotgun
Single shot
Double barrel - side by side or over and under, fires 2 shots at once
Over & under
Bolt action
Lever action
Pump action
Auto-loading - military and police typically
List the features of a shotgun
Smooth barrel
Fired from shoulder
Fires multiple pellets/lead shot
What is the shotgun gauge
The number of balls of lead exactly fitting the barrel (same diameter) which make up 1lb in weight
Describe the structure of shotgun ammunition
Base is a brass head plate
Above is the primer then the powder/propellent
The WAD (cardboard or plastic) sits on top of propellent
Modern guns may use plastic power piston instead of WAD
The shot/projectiles are above
All encased in a crimped plastic tube (rather than metal seen in handguns)
What is the function of the ‘choke’ of the barrel
This is the taper towards the muzzle - decreases in diameter towards the end
It keeps the shot more closely clustered- channels the pellets closer together
How do you measure the choke of a shotgun barrel
Measured as % shot striking within a 30 inch target circle at range of 40 yards
e.g. a full choke is 60% and a normal cylinder is 30% (same diameter all the way down)
What is the function of the shotgun power piston
It pushes the shot out of the barrel but also exits and contributes to the wound
More effective way of channeling the explosive force from propellent
More complex mechanism than traditional WAD - made of plastic and double cupped (upper cup made of petals
Describe the structure of the shotgun power piston in different guns
12 gauge, 16g & 20g have 4 petals
.410 has 3 petals
The petals are closed initially but open up and fall to the sides as fired
The power piston can indicate manufacturer & gauge
At what distance does the shotgun power piston contribute to the wound itself
Below the range of 20ft
It will also strike the body at this range
Describe the appearance of the shotgun power piston at different distances after firing
< 1ft, not yet opened nand will hit body
1-3ft, petals are starting to open and will leave abrasions when they hit
> 3ft, petals folded back and no longer get petal marks
> 8-10ft, strikes of to the side of entry wound
The power piston can indicate manufacturer & gauge
What are the features of a contact shotgun wound to the head
Scalp laceration - hard to construct dimensions of weapon as so massive
Skull fracture - caused by huge energy
Brain may be “blown out” - caused by release of gas
Most pellets & wad may exit
Very mutilating injury due to gas and energy of the shot
What are the features of a contact shotgun wound to the torso
Circular entry wound that matches muzzle diameter
Muzzle imprint
Soot smudging - loose contact
Burning or melting of clothes
Cherry pink wound margin due to carbon monoxide
What are the features of a shotgun wound from various known distances
Below 2ft there is a circular wound matching barrel diameter
Tattooing present up to 3ft but no further
Scalloped margins by 3ft
Satellite holes (fliers) form by 4ft as individual pellets start to spread and central hole gets smaller
Cuff of satellite holes by 6ft - definite shape
How can you estimate the distance of a shotgun from the wound if it was over 10 away
This would require test firing of the suspect weapon
This is because over 10ft the entry wound will vary with the range, length, choke of barrel and the ammunition
At what distance would you get tattooing from a shotgun
Up to 60cm or 24 inches
At what distance would you get smoke/soot on the body from a shotgun
Up to 38cm or 15 inches
At what distance would you get burns on the body from the flame of a shotgun
Up to 15cm or 6 inches
List signs of suicide by gunshot
Contact wound
high velocity blood spatter on steadying hand - blow back from the injury
GS residues on firing hand -hands should be swabbed
Evidence of test firing
Which sex is more likely to commit suicide by gunshot
Males - more likely to use violent methods
It is rare in women (poisoning more common)
List the most common sites for gunshot suicides
Head - 80% of cases
Typically the temple, forehead, mouth or chin
15% of cases are in the chest
5% in the abdomen
What signs should be looked for on the hands of a gunshot case at autopsy
Look for soot, blood or residues (e.g. GSR)
What are some of the issues at autopsy in gunshot cases
Shored or Partial exit wound - can be confusing
Bullet ricochet outwith & within body
Separation of bullet jacket & core - seperate wound tracks
Projectiles may embolise or move
Plastic wad and Al jacket invisible on X-ray
X-ray may magnify projectiles
Snooker ball effect of pellets - bounce off each other and spread around (messes up distance analysis)
What is the function of the WAD
Cardboard or plastic disk that pushes the shots out of the barrel
It also holds them in place before firing
Will also leave the barrel
How does range affect the spread of the bullets
The longer the range the greater the spread of pellets
Contact/close range typically a single hole
Start splitting at around 2 metres
Describe the appearance of a contact shotgun wound
Circular hole wound with a surrounding ring of burns
Describe the appearance of a close shotgun wound (few cms)
Circular entry wound with soot staining around it from the smoke
What is a single shotgun projectile called
A slug
Describe the appearance of high velocity blood splatter
At high velocity the blood sprays out in a fine mist
At lower velocities the drops will be larger
You always X-ray a gunshot victim - true or false
True
Allows you to locate and retrieve projectiles (bullet, pellets etc)
Why is the clothing of a gunshot victim retained
So it can be analysed and tested for things like GSR or blood splatter
Are the individual rifling marks that are specific to one specific gun always the same for that gun
No They are due to wear and tear in the gun and so they will change over the years within the same gun Just because 10 years ago that specific rifling mark was made by that gun doesn't mean it will make the same marks today Its class characteristic rifling marks will be the same though
Are handguns rifled
Yes
What is meant by autoloading in hand guns
That you press the trigger each time and the gun will reloaded the next bullet automatically
Are revolvers autoloading
No
Each time you must pull back a lever to reload
What’s the difference between a shotgun and a rifle
A rifle has a rifled barrel that fires single rifle ammunition
A shotgun has a smooth barrel and fires multiple lead projectiles (balls bearing)
How far does the propellant reach from a gun fired
18 inches
When do discharge gases in particular cause a lot of damage
Especially in close contact with shotguns as gets lots of CO released
how far does the propellant reach from a gun fired
18 inches
If a gun is fired from more than 18 inches away what do you see on the body
Just the bullet entry wound
Everything else doesn’t reach far enough
How can you tell from bone which side the bullet exited through
The wound will be larger on the side of the bone it exited through
Creates an outward cone shape
What does a bullet do to the skin as it exits
It rips through it so the skin will fold outwards
There will be no imprint abrasion as seen at entry wound
How can you tell an entry and exit wound apart
Entry - skin folds inwards and there is imprint abrasion
- the bone hole will be larger in the innermost side of that bone
Exit - skin rips outwards and no imprint abrasion
Bone hole is larger on the outermost surface of that bone
What causes the muzzle imprint in contact shooting
It’s not a direct imprint abrasion from the muzzle itself but is in fact caused by the gas from the firing going into the skin and blowing it back into the gun muzzle
What is bullet wiping
This is when the barrel of the gun hasn’t been cleaned so there is oil, dirt and grease that can be seen in the edges of the bullet track
Wipes off the bullet as it travels
How can you tell apart a hard contact shooting and a loose contact shooting
If hard contact - entry hole is burnt with soot and propellent seared into the edges
Loose contact - The entry hole is still burnt but some soot will escaped outwards to side and will line the hole
What must you be careful of when examining near contact gunshot wounds
The soot ring identifies it as near contact and the soot can be wiped off - may lose evidence if not documented
What firing distances can be a suicide
contact ( on skin) near contact ( up to about 6 inches) intermediate (up to 1 meter to 18 inches)
What is shoring of exit wounds
When there is an abrasion around the exit wound (where there shouldn’t be)
This can occur if the skin was pressed up against a bra or a wall etc.
What is a near exit wound
When the bullet ahs run out of energy and because the skin is stretchy and elastic it hasn’t quite been able to break through
You see a bruise and can feel the bullet underneath
What does a contact entry wound between the eyes suggest
Most commonly suicide
Assassination
What must you not do when removing a bullet from a near exit wound
Do not used toothed forceps as this could ruin the rifle markings
If you have a case where the same bullet has entered/exited more than once (e.g. through arm then through chest) what does it suggest
High velocity rifle with a jacketed bullet
What can cause the skin to split around a bullet wound
The high velocity gases
