Firearm Injuries and Mechanisms
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Questions and Answers

What is the defining feature of rifled weapons that contributes to the bullet's motion?

  • Smooth interior bore
  • Spiral grooves with lands (correct)
  • Large caliber measurement
  • Short barrel design

Which component of a cartridge ignites the propellant powder in the firing mechanism of rifled weapons?

  • The primer (correct)
  • The firing pin
  • The bullet
  • The shell casing

What is meant by the term 'caliber' in the context of rifled weapons?

  • The velocity of the bullet
  • The weight of the bullet
  • The length of the barrel
  • The distance between two opposite lands (correct)

Which of the following is NOT a characteristic of firearm wounds?

<p>Uniformity of tissue damage (C)</p> Signup and view all the answers

What type of powder utilizes nitroglycerine or nitrocellulose?

<p>Double base smokeless powder (B)</p> Signup and view all the answers

Which type of weapon relies on the absence of spiral grooves within the barrel?

<p>Non-rifled weapon (C)</p> Signup and view all the answers

What happens during the rapid burning of the propellant powder in a cartridge?

<p>An enormous amount of gas is produced (B)</p> Signup and view all the answers

What signifies the unique 'family characteristics' of a bullet from a specific weapon?

<p>The pattern of lands and grooves on the bullet (A)</p> Signup and view all the answers

What is the primary effect of gas released during gunfire?

<p>Leads to eversion of wound edges and cruciate lesions (C)</p> Signup and view all the answers

What is the phenomenon called when unburned gunpowder particles enter and deposit in the skin?

<p>Stippling (A)</p> Signup and view all the answers

What type of injury results from the bullet entering the skin and causing direct damage?

<p>Laceration and crushing (D)</p> Signup and view all the answers

How does the lubrication effect manifest at the margin of a gunshot wound?

<p>As a grease ring or mark (B)</p> Signup and view all the answers

What effect does carbon monoxide in the gunfire gases have on tissues?

<p>Leads to a pink coloration in tissues (D)</p> Signup and view all the answers

What causes the wound diameter to shrink after a bullet exits the skin?

<p>Elasticity of the skin (B)</p> Signup and view all the answers

Which effect is caused by the muzzle of a gun when fired close to the skin?

<p>Imprint from muzzle contact (A)</p> Signup and view all the answers

What type of cavity is created by the continued acceleration of air or tissue during a gunshot?

<p>Temporary cavity (A)</p> Signup and view all the answers

What characteristic wound pattern is associated with new shotgun ammunition devices?

<p>Square edged star or capital X-shape (C)</p> Signup and view all the answers

Which factor is the most significant in determining the range of shotgun pellets?

<p>Type of powder (A)</p> Signup and view all the answers

What typically happens to wads traveling over a distance of 5 meters from the gun muzzle?

<p>They will fall to the ground (C)</p> Signup and view all the answers

In the investigation of firearm injuries, which question aims to determine whether the wound is an inlet or an exit?

<p>Is it an inlet or an exit? (A)</p> Signup and view all the answers

What complication is most likely to occur if a firearm injury affects the medulla oblongata?

<p>Instantaneous death (A)</p> Signup and view all the answers

Which statement accurately describes exit wounds produced by non-rifled weapons?

<p>They may occur if pellets strike at an acute angle (D)</p> Signup and view all the answers

What is a possible consequence of a firearm injury to the abdomen?

<p>Hemorrhage or infection (D)</p> Signup and view all the answers

What is a common visible sign of firearm residue on a victim with an entrance wound?

<p>Blackening and tattooing (C)</p> Signup and view all the answers

What is the typical shape of the exit wound caused by a bullet?

<p>Any shape including stellate and cruciate (B)</p> Signup and view all the answers

Which characteristic is true of the inlet wound compared to the exit wound?

<p>Inlet wounds commonly exhibit a regular shape (A)</p> Signup and view all the answers

How does the beveling differ between inlet and exit wounds?

<p>Inlet wounds have internal beveling, exit wounds have external beveling (B)</p> Signup and view all the answers

When a ricochet bullet strikes before entering the body, which consequence is most likely?

<p>The bullet will leave powder marks on the object it hit (B)</p> Signup and view all the answers

What may cause a bullet's inlet wound to take on an 'F' or 'D' shape?

<p>Firing from a distance (C)</p> Signup and view all the answers

Which of the following statements correctly describes marginal abrasions?

<p>They show equal scraping on all sides in perpendicular shots (A)</p> Signup and view all the answers

Which feature is present in an inlet but absent in an exit bullet wound?

<p>Gunshot residue (C)</p> Signup and view all the answers

What characteristic of inlet wounds may change based on near firing or oblique firing?

<p>Size (B)</p> Signup and view all the answers

Which factors significantly determine the extent of injuries caused by a bullet?

<p>The velocity and mass of the bullet (B)</p> Signup and view all the answers

What results from a contact wound where a bullet strikes an area over bone?

<p>A dome-shaped elevation of skin can occur (B)</p> Signup and view all the answers

How do intermediate range wounds differ from distant range wounds?

<p>Intermediate range wounds may exhibit powder stippling (C)</p> Signup and view all the answers

What primarily causes exit wounds to be larger than entrance wounds?

<p>Bullets may expand or tumble while traversing tissues (D)</p> Signup and view all the answers

What is crucial for estimating the distance of a bullet's impact accurately?

<p>Test firing from various distances (A)</p> Signup and view all the answers

What characterizes a contact wound from a sporting gun?

<p>Single circular entrance wound with minimal soiling (B)</p> Signup and view all the answers

Which of the following effects does NOT occur in non-rifled weapons at distances greater than 2 meters?

<p>Presence of burning and blackening (B)</p> Signup and view all the answers

What causes wad wounds in non-rifled weapons?

<p>Non-metallic contents of shotgun cartridges (A)</p> Signup and view all the answers

What happens to the entrance wound's edges when fired from 15 cm up to 2 meters?

<p>Edges become scalloped and crenated (A)</p> Signup and view all the answers

What is the primary indicator of a wound caused by a shotgun at a distance of over 4 meters?

<p>Central entrance hole is notably missing (C)</p> Signup and view all the answers

What occurs immediately after the trigger of a sporting gun is pulled?

<p>The powder ignites and builds up high pressure (D)</p> Signup and view all the answers

What is a typical consequence of a contact wound that involves bone?

<p>Splitting of the skin due to expanding gases (C)</p> Signup and view all the answers

How do the effects of non-rifled weapons differ from those of rifled weapons?

<p>The effects occur at different distances (D)</p> Signup and view all the answers

Flashcards

Shock Waves

The impact of a bullet creates a pressure wave that travels ahead of the bullet, causing tissue compression and injury.

Bullet Velocity and Mass

The speed and weight of a bullet directly impact the severity of the wound. Faster and heavier bullets cause more damage.

Distance from Muzzle

The distance between the gun and the target affects the amount of gunpowder residue deposited on the wound, which helps determine the range of fire.

Type of Tissue

The type of tissue the bullet hits impacts the severity of the wound. Density and elasticity are major factors, with denser tissues causing more damage and more elastic tissues causing less damage.

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Exit Wound

An exit wound is typically larger than an entrance wound because the bullet may deform or tumble as it travels through the body. It usually lacks gunshot residue.

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Firearm Function

The primary function of a firearm is to propel a projectile using the force of expanding gases, which are generated by the explosion of an explosive substance.

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Rifled Weapons

Rifled weapons have spiral grooves inside the barrel, which impart a spin to the bullet as it travels. This spinning motion improves accuracy and range.

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Lands & Grooves

The grooves in a rifled weapon's barrel are called "lands" and the spaces between them are called "grooves". These features leave distinct marks on the bullet during firing.

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Caliber

The caliber of a firearm describes the diameter of the barrel, measured between opposite lands. It is stated in hundredths of an inch or in millimeters.

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Primer Function

The primer in a cartridge contains an explosive substance that is initiated by the firing pin. This ignites the propellant powder within the cartridge, causing the bullet to be propelled.

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Propellant Powder

The propellant powder within a cartridge burns rapidly, generating expanding gases that exert pressure on the bullet, driving it out of the barrel.

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Firearm Wound Characteristics

Firearm wounds exhibit specific characteristics, including tissue damage, entry and exit wounds, powder marks, gunshot residue, and sometimes the bullet itself.

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Bevelling of Bones

Bevelling of bones is a characteristic of firearm wounds, where the entry side of the bone is compressed and the exit side is pushed outward.

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Gas Effect on Wound

The gases released from a firearm upon firing create an outward pressure on the edges of the wound, resulting in a star-shaped or cruciate (cross-shaped) pattern of tissue damage.

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Flame Effect

The hot flame from the firearm can directly burn the target's skin or clothing.

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Smoke Effect on Target

The smoke released from the firearm deposits a black residue, or smut, on the surface of the target, especially when black powder is used.

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Tattooing or Stippling

Unburnt gunpowder particles are propelled into the target's skin by the force of explosion, embedding themselves in the dermis. This leaves a characteristic stippling pattern.

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Bullet Entrance Wound

The bullet's entry into the body creates a wound that is initially larger than the bullet itself due to the skin's stretching. The entrance wound later shrinks due to the skin's elasticity, leaving a final diameter smaller than the bullet.

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Grease Ring

Lubricant used in the gun barrel and on the bullet can be transferred to the wound margins, leaving a visible grease ring.

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Metal Fragments

Tiny fragments of metal from the gun barrel or the bullet itself can become embedded in the skin, forming gunshot residue.

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Muzzle Effect

The muzzle of the gun can leave an imprint on the skin due to direct contact or pressure from the expanding gases.

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Bullet Inlet

The entrance wound of a bullet, characterized by smaller size, inverted edges, and the presence of gunpowder residue, often referred to as the entry point.

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Bullet Exit

The exit wound of a bullet, characterized by a larger size, everted edges, and absence of gunpowder residue.

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Bullet Inlet Shape

The shape of the bullet wound at the entrance point, typically round or oval, depending on the angle of impact.

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Bullet Exit Shape

The shape of the bullet wound at the exit point, often irregular and can vary drastically, from round or oval to stellate (star-shaped), slit-like, or cruciate (cross-shaped).

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Internal Bevelling

The inward beveling of the bullet wound at the entrance point, where the bullet has pushed bone fragments inwards.

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External Bevelling

The outward beveling of the bullet wound at the exit point, where the bullet has pushed bone fragments outwards.

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Bullet Grazing Wound

A wound created when a bullet grazes the skin and subcutaneous tissue without fully penetrating the body, often forming an elongated or oval mark.

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Ricochet Wound

A wound created when a bullet ricochets off a firm object before entering the body, often resulting in deformed bullet shapes and irregular wounds.

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Choking in a shotgun

A narrowing of the shotgun barrel near the muzzle end that keeps pellets together over a longer distance, modifying the spread of pellets.

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Range of fire

The distance between the firearm and the target at the time of discharge.

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Wads in gunshot wounds

Wads from shotgun ammunition can be found within the wound, within 2 meters of the muzzle.

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Exit wounds in shotguns

Exit wounds are uncommon in shotguns, except when pellets strike the body at an acute angle or near firing range.

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Complications of firearm injury

Immediate death, laceration of the brain, paraplegia (neck injury), instant death (medulla oblongata), blood loss, hemorrhage, infection, peritonitis (abdomen injuries), fat embolism (long bones), pulmonary embolism (immobilization).

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Firearm residue on victim

Visible blackening, grease, tattooing, burning, or invisible residue from primer, powder, metal parts of the bullet or cartridge case.

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Investigation for firearm injuries

Used to determine the type of weapon, the range of fire, and the circumstances of injury.

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Shotgun vs. Rifled Weapon

A specialized weapon designed to fire pellets, creating a pattern of smaller projectiles rather than a single bullet.

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Multiple Exit Wounds

Multiple exits occur when the bullet fragments, jacket separates, bones fracture and exit separately, or two bullets are fired at the same point.

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Contact Wound

A contact wound is characterized by a single circular entrance wound, minimal soiling and burning, a muzzle imprint, and pink tissue due to carbon monoxide. It may also contain wads within the wound.

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Cruciate Lesion

In a contact wound over bone, the expanding gases may split the skin, creating a characteristic cruciate lesion.

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Range of Firing: 0-15 cm

Within 0-15cm, the wound is usually circular, but can be elliptical if the gun is angled. Hair around the wound is singed, and there is burning, blackening, and pink coloration due to carbon monoxide. Wads may also be found.

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Range of Firing: 15cm-2 meters

Between 15cm and 2 meters, the wound edges become scalloped and crenated, resembling a moth-eaten appearance.

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Range of Firing: 2 meters-4 meters

Beyond 2 meters, there is no burning or blackening, and powder tattooing is rare. Individual pellet holes (satellites) appear around the main wound and progressively increase with distance.

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Range of Firing: More than 4 meters

At more than 4 meters, only individual pellet holes are present, and the central hole is absent. This is known as full dispersion.

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Wad Wounds

Wad wounds are caused by non-metallic components of shotgun cartridges and can range from minor bruises to fatal lacerations.

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Study Notes

Firearm Injuries

  • Firearm injuries are caused by weapons designed to propel a projectile using expanding gases produced by explosive combustion.
  • Rifled weapons have spiral grooves in the barrel (lands and grooves) that spin the projectile, giving it a spiraling motion. The caliber is the barrel's diameter, measured in hundredths of an inch or millimeters, using the distance between opposite lands.
  • Rifled weapons can be long-barreled (rifles) or short-barreled (handguns like revolvers or pistols).
  • Non-rifled weapons (like shotguns) use pellets.

Mechanism of Firing Rifled Weapons

  • A primer ignites the explosive charge, creating a high-pressure gas.
  • The high-pressure gas propels the bullet out of the barrel.

Gunpowder

  • Black powder is composed of C, S, and KNO3.
  • Smokeless powder (modern gunpowder) contains nitroglycerine and nitrocellulose.
  • Primers consist of lead azide, lead styphnate, mercury fulminate, lead thiocyanate, and antimony sulfide.

Characteristics of Firearm Wounds

  • Tissue damage or defects (cavitations, loss of substance) occur at the inlet and exit points and along the track.
  • Powder marks, gunshot residue, and bullet/shot presence are external characteristics.
  • Bone margins might exhibit beveling.

Effects of Gunfire

  • Gases, flame, smoke, gunpowder, and metallic fragments alter the skin and clothes.
  • Gases cause eversion of wound edges, creating a cruciate shape lesion.
  • Flame causes burning.
  • Smoke produces blackening/smudging.
  • Unburned particles (tattooing/stippling) are deposited in the skin.

Bullet Effects

  • The bullet causes tissue damage by laceration/crushing.
  • Cavitation creates permanent and temporary cavities due to air/tissue displacement.
  • Shock waves from the bullet travel ahead, compressing the tissue.
  • The trajectory of the bullet through the body can modify the wound shape.

Factors Affecting Injuries

  • Bullet velocity and mass.
  • Bullet design.
  • Distance from the muzzle to the target.
  • Tissue type (density and elasticity). A higher density tissue results in greater damage. A higher elasticity tissue results in less damage.
  • Bullet tumbling.

Range of Firing

  • Contact wounds: Soot, muzzle imprint, laceration of skin
  • Contact wounds over bone: Gases are reflected, creating a dome effect.
  • Intermediate/close-range: Marked powder stippling.
  • Distant range: Lacking stippling; hole roughly the caliber size. Distance depends on residue dispersion and barrel length..

Exit Wounds

  • Generally larger than entrance wounds due to bullet expansion/tumbling.
  • May not exhibit gunshot residue.
  • Trajectory path may be altered by bone or other firm tissues.
  • Exit wounds may not be directly opposite entrance wounds.

Differences between Inlet and Exit

  • Inlet: More tissue loss, inverted edges (except in near firing cases), round/oval shape, present powder marks .
  • Exit: Less tissue loss, everted edges, any shapes (e.g., round, stellate), absent powder marks, irregular.

Bevelling of Bone

  • Bullets displace bone fragments in the direction of travel, creating an internal or external beveling in the skull and other bones (sternum, iliac crest, scapula, ribs)

Direction of Firing

  • Perpendicular firing creates a rounded inlet wound with marginal abrasions uniformly distributed.
  • Angled firing creates an oval inlet with abrasions on one side closer to the gun.
  • Grazing wounds occur when the bullet grazes the skin/subcutaneous tissue without penetrating.

Special Forms of Firearm Wounds

  • Inlet wounds: D or F shape due to tumbling.
  • Ricochet: Bullet hits an object before the body, leaving powder marks.
  • Multiple exits: Bullet breaks into multiple pieces or parts of the jacket separating and causing multiple exits.
  • Bone fracture fragments: Fragments emerge out of the body.
  • Successive firing: Two or more bullets entering at same point, different exits

Mechanism of Firing Sporting Guns

  • Trigger activates the primer.
  • Primer ignites the powder.
  • Gas pressure pushes the wad and pellets forward.
  • Pellets, flame, smoke, and unburned gunpowder affect the skin.

Effects of Gunfire in Non-Rifled Weapons

  • Effects of gases, flame, and smoke are similar to rifled firearms, but occur at different distances
  • Effects of pellets and wads depend on distance.

Range of Firing in Non-Rifled Weapons

  • Contact wounds: Single circular entrance wound, minimal soiling/burning, muzzle imprint.
  • Beyond 2 meters: Wads may fall to the ground. Distance affected by choking, barrel length, pellet size, and gauge

Investigation for Firearm Injuries

  • Determine if injury is from firearm.
  • Identify the type of injury.
  • Establish the firing range.
  • Detail circumstances of event.
  • Identify the weapon.

Complications and Sequel of Firearm Injuries

  • Depends on injury site, blood vessels and organs involved.
  • Contact or near range firing may result in immediate death.
  • Brain laceration.
  • Neck injury could result in delayed death or paraplegia, if involved medulla oblongata = immediate death.
  • Chest injuries can cause death from blood loss, leading to circulatory collapse .
  • Abdomen injuries: hemorrhage, infection, peritonitis could cause death
  • Long bone fracture can cause fat embolism to occur.
  • Long immobilization could lead to pulmonary embolism.

Firearm Residues

  • Visible residues include blackening, grease, tattooing, and burning
  • Invisible residues related to primers and gunpowder.
  • Residues can be found on clothing, skin, and objects at the scene.
  • Common elements found in modern gunpowder and primers are lead, barium, and antimony.

X-Ray Use

  • Locates bullet/pellet/fragments
  • Delineates trajectory
  • Identifies defects in bone
  • Rules out missile presence

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Firearm Injuries PDF

Description

This quiz covers the fundamental aspects of firearm injuries, including types of weapons and their mechanisms. It explains the structure and function of rifled and non-rifled firearms, as well as the chemistry of gunpowder. Test your knowledge on the science behind these important concepts.

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