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Ballistics > Wounding > Flashcards

Wounding Flashcards

At the conclusion of this section students should be able to: • • Identify the main classifications of gunshot wounds • Explain the factors that contribute to the extent of gunshot wounds • Explain the significance of the temporary cavity in wounding. • Differentiate entry and exit gunshot wounds

1
Q

What is Wound Ballistics?

A

Wound ballistics can be considered a subdivision of terminal ballistics Which deals with the motions and effects of projectiles in tissue.

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2
Q

The extent of injury from a bullet is attributable to:

A
  1. The mechanical shredding and crushing of tissue by the bullet as it perforates the tissue.
  2. Shearing, compression and stretching injuries to the tissue due to temporary cavity formation.
  3. Secondary issues due to the breakup of the bullet
  4. The nature of the tissue perforated by the bullet
  5. The length of the wound track
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3
Q

Temporary Cavity

A

A cavity which is formed when the kinetic energy of a projectile is transferred to the surrounding tissue causing it to expand outwardly.

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4
Q

How long until the cavity collapses ?

A

The cavity collapses after a few seconds and is again filled with surrounding tissue and fluid.

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5
Q

The are the factors that affect the size and shape of temporary capvity

A
  • Nature of the bullet
  • The amount of kinetic energy lost by the bullet in its path
  • How rapidly the energy is lost
  • The elasticity and cohesiveness of the tissue
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6
Q

What is not a significant TC in wounds caused by which firearm?

A

The temporary cavity is not as significant in wounds caused by handgun bullets as with rifle bullets.

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7
Q

How does the organ the projectile hit effect the temporary cavity?

A

No matter how large the temporary cavity is, it will have little or no effect unless it forms in an organ sensitive to injury from such a cavity (eg. liver vs muscle).

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8
Q

How doe the location of the wound play a important role in the severity of the injury.

A

Specific organs like elastic tissue such as muscle or the lung are more resistant to stretch damage as opposed to solid organs such as the liver.

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9
Q

How does kinetic energy determine the size of the temporary cavity?

A

It is the amount of kinetic energy lost in the tissue that determines the size of the temporary cavity and not the total energy possessed by the bullet.

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10
Q

What factors that affect kinetic energy lost ?

A
  1. Yaw of the bullet at the time of impact
  2. Bullet Characteristics
  3. Location of the wound
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11
Q

What is the yaw of the bullet?

A

The yaw of the bullet is the deviation of the long axis of the bullet from its line of flight. As soon as the bullet leaves the barrel it begins to yaw or wobble.

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12
Q

What physical characteristics of the bullet affect the yaw?

A

The degree of yaw of a bullet is determined by its physical
characteristics of the bullet, the rate of twist and the density of the air.

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13
Q

How does the gyroscopic spin become insufficent?

A

Although the gyroscopic spin imparted by the rifling is sufficient the bullet in air, it is insufficient to stabilize the bullet when it enters the body.

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14
Q

How is kinetic energy lost in the wound by yawing?

A

As the bullet begins to yaw, its cross-sectional area becomes larger, the drag forces increases and more kinetic energy is lost in the wound. The sudden increase in the drag force on yawing puts a great strain on the bullet may cause it to break up.

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15
Q

What bullet characteristics can influence the amount of kinetic energy lost in the body?

A

The bullet characteristics such as its calibre, construction and configuration can influence the amount of kinetic energy lost in the body.

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16
Q

How does the type of bullet affect kinetic energy in the body?

A

Expanding bullets, which open up or mushroom in tissue, are more retarded by tissue than round nose bullets and therefore lose greater amounts of kinetic energy in the body.

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17
Q

As the bullet deforms what characteristics are affected?

A

As the bullet begins to deform, the shape and calibre of the bullet play less of a significant role in the amount of kinetic energy lost in the body.

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18
Q

What does bullet deformation depend on?

A

The amount of deformation depends on the construction of the bullet( length, thickness, hardness of the jacket material, hardness of the lead core and the presence of a hollow point) and the bullet velocity.

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19
Q

How does the density of the tissue affect the energy lost ?

A

The denser the tissue then the greater the retardation and greater the energy lost in the body.

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20
Q

What parts of the tissues directly affects the amount of kinetic energy lost?

A

The density, strength and elasticity of the tissue penetrated by a bullet as well as the length of the wound track plays a significant role in determining the amount of kinetic energy lost in the body.

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21
Q

How can handguns produce significant damage?

A

To cause significant damage, a handgun bullet must strike a structure directly.

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22
Q

How big can temporary cavities of rifle bullets get?

A

Temporary cavities created by rifle bullets can reach up to 12.5 times the diameter of the bullet.

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23
Q

What effect does expanding cavity walls have, and how does pressure introduce foreign materials?

A

The expanding walls of the cavity are capable of causing severe damage. Positive and negative pressures alternate in the wound track, resulting in the sucking of foreign matter and bacteria into the track from both the entrance and exit.

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24
Q

Where is maximum kinetic energy lost?

A

Maximum kinetic energy lost occurs at the point where the bullet is in maximum yaw i.e., at a 90 degree angle to the path.

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25
Q

How does permanent cavities form?

A

Less elastic and cohesive structures struck by high velocity bullets results in a permanent cavity approximately the size of the temporary cavity.

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26
Q

What is the critical level of kinetic energy and why is it important?

A
  • There is a critical level of kinetic energy loss above which tissue destruction becomes radically more severe.
  • When a bullet exceeds this level , it produces a temporary cavity that the organ or tissue can no longer contain. When the
  • Elastic level is exceeded the organ bursts.
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27
Q

What is the critical level exceeded for a full metal jacket projectile?

A

For full metal jacketed bullets this critical level is exceeded when the projectile reach velocities greater than 2625 – 2950 ft/s.

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28
Q

What is the critical level exceeded for a soft point or hollow point rifle bullets?

A

For soft point or hollow point rifle bullets, the the critical level can be reached at lower velocities as a result of the deformation and breakup of the bullets.
Therefore, the critical velocity can be 1500 – 2000 ft/s.

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29
Q

What are the four categories into which gunshot wounds can be dvided

A
  • Contact Wounds
  • Near Contact Wounds
  • Intermediate Wounds
  • Distant Wounds
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30
Q

What is contact wounds?

A

A contact wound refers to a wound that is created when the muzzle of the firearm is held against the surface of the body at the time of discharge.

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31
Q

What are the main types of contact wounds?

A

These type of wounds can be divided into:
*hard,
*loose,
* angled
* and incomplete wounds

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32
Q

What substances are deposited in and along the wound tract in contact wounds ?

A
  • Soot
  • Powder
  • Vaporized metals
33
Q

What are hard contact wounds?

A

Hard contact wounds, the muzzle of the weapon is pushed hard against the skin indenting, so that the skin envelopes the muzzle.

34
Q

What are the characteristics of hard contact wounds?

A
  • Seared edges
  • Edges blackened by soot
  • Soot around edges cannot be completely removed either by washing or vigorous scrubbing of the wound.
35
Q

What is loose contact wounds?

A

Loose contact wound is created when the muzzle is held lightly against the skin.

36
Q

What are some characteristics of loose contact wounds?

A
  • Soot deposited around the entrance
  • Soot can be easily wiped away
  • Unburnt grains of powder deposited on the skin in the zone of soot
37
Q

What is angled contact wounds?

A

This type of contact wound, the barrel is held at an acute angle to the skin, so that the entire circumference of the muzzle is not in contact with it.

38
Q

What are the characteristics of angled contact wounds?

A
  • Conspicuous blackened seared area of skin having a circular or oval shape
  • Less conspicuous larger fan-shaped zone of light grey soot that radiate outward from the gap
  • Light zone of soot easily washed or wiped away
  • Unburnt grains of powder deposited around the wound
  • Blackened seared area on the opposite site of the wound from the muzzle
39
Q

What is incomplete contact wounds?

A

This type of contact wounds the weapon is held against the skin but because the surface is not completely flat there is a gap between the muzzle and the skin.

40
Q

What are the characteristics of a incomplete contact wounds?

A

A jet of soot-laden gas escapes from this gap producing an area of seared, blackened skin.

41
Q

What cases are incomplete contact wounds seen?

A

These types of gunshot wounds are most often seen in self inflicted gunshot wounds of the head due to long arms. In these cases, the zone of blackened and seared skin usually extends downward from the entrance.

42
Q

What are near contact wounds?

A

Near contact wounds lie in the zone between contact and intermediate range wounds. This type of contact wound the weapon is not held against the skin but a short Distance away.

43
Q

Which of the contact wounds are similar to near contact wounds?

A

Near contact wound type of contact wound can be difficult to differentiate from Loose contact wound

44
Q

What are the characteristics of near contact wounds?

A
  • Wide zone of powder soot overlying seared, blackened skin
  • Soot is baked into the skin and cannot be completely wiped away
  • Small clumps of unburned powder present in seared zones
45
Q

What is near contact angled wounds?

A

The near contact wound is where the barrel is held at an acute angle with the muzzle a short distance away from the skin.

46
Q

What are the similarities and difference of near contact angled wounds and angled wounds?

A

Just as in angle contact wounds soot radiates outward from the muzzle creating a circular or irregular shaped blackened seared zone and a light gray fan-shaped. However, unlike angle contact wounds the bulk of the seared blackened zone is on the same side as the muzzle.

47
Q

What is intermediate range wounds?

A

This type of gunshot wound is one in which the muzzle is away from the body at the time of discharge yet close enough to produce “powder tattooing” .

48
Q

What is powder tattooing?

A

“powder tattooing” as a result of powder grains being expelled from the muzzle with the bullet creating reddish-brownish punctuate lesions surrounding the entrance wound.

49
Q

What does powder tattooing indicate?

A

Powder tattooing in an antemortem phenomenon and indicates that the
Individual was alive at the time they were shot.

50
Q

How can you tell if a person was dead before they were shot?

A

If the individual was dead before being shot, even though powder marks may be produced, they will have a moist gray or yellow appearance rather than reddish-brownish.

51
Q

How does powder grains impacts powder tattooing?

A

Powder tattooing are not “powder burns” as often suggested but are rather created by the impact of powder grains on the skin resulting in punctuate abrasions.

52
Q

What is distant gunshot wounds?

A

Distant gunshot wounds, the marks produced by the interaction of the bullet and the skin are the only marks present.

53
Q

What is entrance wounds?

A

An entrance wound is said to be round to oval with a reddish –Brownish margin of abraded skin (abrasion ring).

54
Q

What is another way in which entrance wounds may appear?

A

A fresh entrance wound may also have a punched-out appearance with no abrasion zone with immediate transition from normal appearing skin to shiny pale dermis (this is often seen in centre fire rifle bullets and high-velocity jackets handgun bullets).

55
Q

What is the main difference between an entrance and exit wound?

A

Exit wounds are typically larger than entrance wounds

56
Q

Why are Exit wounds are typically larger than entrance wounds?

A
  • The tumbling or yawing of the bullet is accentuated and the bullet may even start to travel base first.
  • The retardation of the bullet by tissue may cause the bullet to deform.
    *Steel balls fired in the skin will not tumble like bullets and lose some energy at the time of exit causing a smaller wound than the entrance.
  • An exiting bullet will be undeformed and with its long axis perpendicular to the skin, creating a perfectly round exit wound. In both these instances it may be indistinguishable from an entrance.
57
Q

What are the characteristics of exit wounds?

A

These include:
* They are typically larger than and/or more irregular than entrance wounds
* Do not possess an abrasion rings (exception to this is with shored exit wounds)

58
Q

What are other factors that can be used to differentiae between entrance and exit?

A
  • Once a wound has an abrasion ring that it can be easily identified as an entrance. (With exception of the palm, sole and elbow, these wounds are oval to circular)
  • With a punched out clean appearance to the margins, totally unlike that of exit wounds. (The exception to this are re-entry wounds.)
  • In rare instances, a circular punched-out entrance without an abrasion ring is associated with an exit that also has a circular punched out appearance.
59
Q

What are re entry wounds?

A

Re-entry wounds occur when a bullet perforates one part of the body then Re-entered another part of the body.

60
Q

How are re entry wounds categorised?

A

Re-entry wounds are typically characterized by a large irregular entrance hole, whose edges a ragged and has a wide, Irregular abrasion ring.

61
Q

What is a cylinder gap?

A

If a revolver is held parallel to the body at the time of discharge, the jet of gas escaping from the gap between the cylinder and the barrel (cylinder gap).

62
Q

What kind of shape soot may a cylinder gap produce?

A

May produce a L-shaped or V-shaped grey sooty deposit on the skin or clothing.

63
Q

When powder escapes the cylinder gap what occurs?

A

Powder escaping from the cylinder gap may also result in tattooing of the skin. This tattooing however may be relatively sparse.

64
Q

What can happen is the barrel and the cylinder is out of line?

A

If the barrel and cylinder is out of line, fragments of the bullet may be sheared off are the bullet jumps from the cylinder to the barrel. These fragments can produce marks on the on the skin that resemble tattooing.

65
Q

What are flash suppressors?

A

Flash suppressors are attached to the muzzle of firearms and are are used to reduce the muzzle flash that can be seen when a firearm is discharged, especially at night.

66
Q

How is muzzle flash determined?

A

Muzzle flash is determined by the type of propellant, barrel length and muzzle pressure among other factors.

67
Q

What type of contact wound does the muzzle of a flash suppressor make?

A

If the muzzle of the weapon is held in contact with the body at the time of discharge, the flash suppressor will produce a distinctive pattern of seared, blackened areas around the entrance wound. When fully formed it results in a flower-like pattern of soot and seared skin.

68
Q

What are microtears?

A

Wounds from high-velocity centrefire rifle bullets may show small splits or tears radiating outward from the edges of a entrance wound. They may involve only a partial circumference of the entrance wound and are barely visible with the naked eye.

69
Q

What projectile can produce a mircotear?

A

These micro tears, though rarely, may also be seen from partial metal-jacketed high velocity pistol bullets.

70
Q

How does an Intermediary Targets affect the appearance of a wound?

A

The appearance of a wound may be altered as a result of the bullet passing through an intermediary target before striking a victim. This normally results in an alteration to the appearance of the wound or wounds.

71
Q

When passing through an intermediary object what may propel off the projectile and how does this affect wounds?

A

In passing through an intermediary object a bullet may propel fragments of the object forward with the bullet. This may result in fragments from the object being embeded in the skin as well as produce pseudopowder tattoo marks on the skin.

72
Q

What is a keyhole entrance wound?

A

A bullet striking the skull at a shallow angle may produce a keyhole wound of the bone.

73
Q

How is a keyhole shaped wound made?

A

The stress created when the bullet comes into contact with the bone, part of the bullet shears off and travels a short distance beneath the the scalp while the bulk of the bullet enters the cranial cavity. This results in a keyhole-shaped wound in the bone.

74
Q

What is back spatter?

A

Back spatter is the ejection of blood and tissue from a gunshot wound
entrance. The occurrence and degree of back spatter depends on the location of the wound, the range and calibre of the weapon.

75
Q

What is back spatter in contact wounds?

A

back spatter refers to blood that is ejected rearwards towards the line of fire.

76
Q

What information can be received from back spatter on the hands?

A

It can be presumptive evidence that someone has fired a gun. This is especially so when it is found on the firing hand. While its presence may indicate that the person fired the gun, absence of back spatter does not mean they did not.

77
Q

Where on the firearm should be checked for blood or tissue?

A

It is most often detected on the outside of the muzzle than inside of the barrel.

78
Q

What does blood inside the barrel suggest?

A

The weapon was within a few inches of the body at the time of discharge.

79
Q

How can you determine the calibre of the bullet?

A

The calibre of a bullet cannot be determined by the diameter of the entrance wound. The size of the hole is due to the elasticity of the skin and the location of the wound, and not just the diameter of the bullet.

Ballistics (11 decks)

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