Tuesday, March 1, 2005 - 7:30 PM
Convention Center, Room 006 A,B
Kim A. Collins
Medical University of South Carolina
Bexar County Medical Examiner's Office
University of Texas Health Science Center, San Antonio, TX
Kim A. Collins
Medical University of South Carolina
The History of Warfare - An Overview
- The severity of a wound is determined by two factors: the amount of tissue shredded by the bullet as it "cuts" its' way through tissue and the amount of Kinetic Energy lost by the bullet in the body. The greater the kinetic energy lost by a bullet in the body, the greater the amount of tissue damaged and thus, the severer the wound.
- Kinetic energy possessed by a bullet:
K.E. = W x V2 / 2G
W = Weight of bullet
V = Velocity of bullet
G = Gravitational acceleration
- It is not the kinetic energy possessed by a bullet prior to entering a body that determines the severity of a wound, but rather the amount of this energy lost in the body.
- As a bullet passes through the tissue, it imparts a radial motion to the tissues surrounding the path (i.e. it hurls the surrounding tissue away), thus creating a temporary cavity much larger than the permanent cavity. The lifetime of this cavity is 5-10 milliseconds. In the case of centerfire rifles, the pressure waves produced by high velocity projectiles can cause injuries to blood vessels, nerves, organs and bones at a considerable distance from the path of the bullet. For handguns, the temporary cavity phenomena plays virtually no role in wounding.
HIGH VELOCITY RIFLE WOUNDS
- Discharge of a Gun
On discharging a gun, the following material leaves the barrel:
This material can have an effect on the appearance and extent of a wound.
- The bullet
- A flame at 1400 F
- Powder: burning and unburnt
- Metal vaporized from the bullet and jacket
- Primer compounds (lead, antimony and barium)
- Copper and nickel vaporized from the cartridge case
- Types of Wounds
- Contact Wounds
- The muzzle is in contact with the body.
- Contact wounds are either: hard contact or loose contact. In loose contact wounds, there is a wide zone of soot deposited around the entrance.
- In contact wounds, there is:
- Scorching of the wound edges
- Soot (powder blackening) deposited on the wound margins.
- Soot and powder particles are driven into the wound track.
- In contact wounds, there may be:
- A muzzle impression, due to blow-back of the skin, caused by the gases.
- Soot on the skin adjacent to the wound.
- Singeing of adjacent hair (rare).
- In contact wounds over bone, such as in the head:
- A stellate wound of entrance is often produced by subcutaneous expansion of the powder gases between the skin and bone.
- Soot is deposited around the entrance in the bone.
- Soot may also be deposited on the inner surface of the skull and on the dura.
- In contact wounds over clothing, the clothing may absorb all the external soot and powder. Powder grains and soot will still be inside the wound track, however.
- Near Contact Wounds
- This is a transition wound between loose contact and intermediate wounds. The entrance hole is surrounded by a wide band of seared and blackened skin. Deposits of powder may be present in this zone.
- Intermediate Range Gunshot Wounds
- The range is greater than contact, and near contact, but close enough to have "powder tattooing" of the skin.
- Powder tattoo marks are punctate abrasions of the skin due to impact of unburnt and burning grains of powder in the skin. They are not burns.
- Maximum range for powder tattooing depends on the physical form of the gunpowder, the barrel length and to a lesser degree the caliber.
- Powder tattooing from rifles and shotguns is less dense than due to handguns.
- The size and density of the powder tattoo pattern can be used to determine the range. The same weapon and ammunition should be used, as powder patterns are variable from gun to gun and ammunition to ammunition.
- Soot (powder blackening) is present on close-up gunshot wounds out to a maximum of 12 inches for handguns.
- Soot can usually be wiped off, but powder tattooing cannot be.
- Hair and clothing may interfere to some degree with powder tattooing. All clothing should be examined.
- With centerfire handguns, powder tattooing usually extends out to approximately 2 feet for flake powder, 3 feet for flattened ball and 4 feet for ball powder.
- Distant Wounds
- Range greater than intermediate. No soot or powder tattooing present.
- Exact range cannot be determined.
- Entrance wound can be differentiated from exit by virtue of the abrasion ring
- Virtually all entrance wounds have an abraded margin, called the "abrasion ring". This is due to the bullet scraping the margins of the bullet hole as it perforates the skin.
- The abrasion ring is present in contact, near contact, intermediate and distant gunshot wounds.
- Symmetrical abrasion rings suggest a head-on shot and eccentric rings, an angled shot. This is not absolute, however. The course of a bullet can only be determined by an internal examination of the body.
- On occasion, entrance wounds do not have abrasion rings but rather present with a punched out appearance. These wounds may have micro-tears. They are usually due to semi-jacketed/jacketed high velocity bullets e.g. the .357 Magnum, rarely 9mm.
- Except for contact wounds over bone, entrance wounds tend to be small, circular or oval, and regular.
- On occasion, a distant wound may have a stellate appearance. Such wounds are almost invariably head wounds over bony prominences or curved surfaces.
- One cannot tell the caliber of a bullet by the entrance hole in the skin, due to the elasticity or lack of elasticity of the skin.
- Exit Wounds.
- These are usually larger and more irregular than entrance wounds. This is due to:
- Bullet tumbling.
- Bullet deformation.
- Some exit wounds may appear slit-like resembling stab wounds
- There is usually no abrasion ring.
- Rarely an abrasion ring is present at an exit. This occurs when the exit is shored up by a firm object, such as a belt, a wall, the floor, clothing, etc.
- Bullet Wound of Bone.
- Entrance: punched out, circular to oval hole with sharp edges. The opposite surface is beveled. Therefore, in skulls, the entrance bullet hole is beveled inward.
- Exit: beveled or cratered. In skulls, the exit hole is beveled outward.
- If a bullet hits and perforates a bone at a shallow angle, a combined entrance-exit or "keyhole" wound may be produced.
- Bullet holes in bone from full metal-jacketed bullets tend to be the same diameter as the bullet. Lead or partial metal-jacketed bullets can produce holes up to twice the diameter of the bullet.
- Bullet Wipe
- A grey ring around the entrance hole in skin or clothing, due to grime on the bullet being wiped off on the skin or cloth as the bullet enters.
- Occurs with both revolvers and automatic pistols.
- Must not be mistaken for soot on the wound margin.
- Miscellaneous points
- Cannot tell caliber of a bullet from an x-ray of it in the body, due to x-ray distortion.
- The trajectory of the bullet through the body is dependent on:
- The position of the victim.
- The position of the assailant.
- The angle the weapon was held.
- Wounding Potential
- Much greater than handguns, due to the greater kinetic energy possessed by the bullets as a result of high velocities.
- Cause very severe injuries to the skull and internal organs of the torso. External injuries of the torso usually appear no different from handgun wounds.
- The temporary cavity may fracture bones, injure vessels and organs without the bullet directly striking them.
- General Wound Characteristic
- Same as in handguns, but the internal injuries are much more severe. The entrance may lack an abrasion ring and show "micro-tears".
- Powder tattooing disappears by 1 1/2 feet for cylindrical powder and 3 feet for ball powder.
- Soft-point hunting bullets shed lead as they go through the body, creating a "lead snowstorm".
- High velocity rifle bullets exit as a rule.
- 5-6% of right-handed individuals, who use a handgun to commit suicide, shoot themselves in the left temple, using the left hand to fire the gun and steadying the barrel with the right.
- Multiple bullet wounds do not rule out a suicide. One woman shot herself nine times in the chest, while a man shot himself five times in the head.
- A fatal "accidental" shooting by an individual while "cleaning" a gun is almost always a suicide.
- Suicide notes are present in only 25% of cases.
- Backspatter (blowback) of blood on the firing hand occurs in about 33-35% of cases involving handguns.
- The gun is found clutched in the hand in 20% of the cases involving long arms and 25% of the cases handguns.
- Occasionally individuals shoot themselves in the back of the head
- There are two methods of analysis for gunshot residue in current use: atomic absorption spectrometry (AAS)and scanning electron microscopy with energy dispersive x-ray (SEM-EDX).
- SEM-EDX is more suitable for detecting gunshot residue on the hands of suspects than on the hands of deceased individuals.
- A shotgun is a smooth-bore, shoulder-fired firearm. It is usually used to fire multiple pellets, rather than a single slug. The most common gauges (caliber) with their corresponding bore diameters:
| GAUGE || DIAMETER (Inches)|
| 12 || .729|
| 16 || .662|
| 20 || .615|
| .410 || .410|
- The pellets fired range in diameter from .08 inches for No. 9 shot to .33 inches for 00 Buck. A wad or wads which may be either paper or plastic, lie in between the shot pellets and the powder. Most modern shells use plastic wads. These wads may be any color. A shotgun shell can contain anywhere from a couple of hundred pellets to nine for 00 Buck, or one large lead slug. Most buckshot and Magnum birdshot shells contain a white plastic filler.
- Choke: The choke is a partial constriction of the bore of a shotgun barrel at its muzzle end that controls the size of the shot patterns.
- Entrance Wounds
- Close-range wounds (contact and close-up): From contact to 12 inches, there is a single round entrance, 3/4 to 1 inch in diameter. The edge of the wound shows an abrasion ring. As the distance between muzzle and skin increases, powder tattooing appears. Powder blackening is most prominent at less than 12 inches. Powder tattooing is considerable less dense than in pistol wounds.
- Powder tattooing extends out to 3 feet (90 cm) for Winchester ammunition which is loaded with ball powder and out to 2-2 1/2 feet (60-75 cm) for other cartridges which are loaded with flake powder. Plastic filler found in some shells may produce stippling marks on the skin that appear identical to powder tattoo marks. These marks, however, may be produced out to 6-8 feet in contrast to powder tattooing.
- At 3 feet of range, one usually has a circular wound of entrance with scalloped margins.
- At 4 feet of range, there is a large central entrance with scalloped or ragged margins and a few satellite pellet holes.
- Distant range: Beyond 10-12 feet., there is great variation in the spread of the pellets depending on the choke of the weapon.
- The Wad
- At close range, the wad will be propelled into the body through the large single entrance wound.
- Beyond approximately 10 ft., the wad will have separated from the pellets and will not enter. It may mark the skin adjacent to the entrance.
- Retain the wad and representative pellets. The gauge of the shotgun and the size of the pellets can be obtained from examining wad and pellets, respectively. The manufacturer of the ammunition can be determined from the wad.
- Rarely, a plastic wad may be marked by the choke or irregularities at the end of the barrel (especially in a sawed off-shotgun) making ballistic comparison possible.
- Range Determination
- These can be made by duplicating on paper the size of the shotgun pattern described at autopsy. The same weapon with the same type ammunition must be used in duplication of the pattern if accurate results are desired. Range formulas do not work.
- X-ray patterns of shot in the body are useless for range determinations.
- Patterns on the body in which the shot first struck an intermediate target are useless for range determinations.
- The size of the shot pattern on the body is dependent primarily on the range, the choke of the gun and the type of ammunition. The barrel length is a minor factor.
- The size of the pellet pattern is independent of the gauge of the shotgun. An increase in gauge just increases the density of the pattern.
Di Maio, V.J.M. GUNSHOT WOUNDS, 2nd edition, CRC Press, Boca Raton FL, 1999