Test 1 - #4 Firearm Injuries
when the entrance is supported by another portion of the body
"shored" entrance wounds
what are the different possible ranges of fire and what do their entrance wounds typically look like
-contact (stellate) -close range/intermediate range (circular with other small satellite injuries surrounding) -distant range (circular)
contact wounds and distant range wounds can both contribute to skull fractures but for different reasons:
-contact = gases entering the cranium and expanding -distant = fractures produced by pressure from the temporary cavity formation
secondary fractures of the skull (bullet enters skull and then enters brain and the brain swells and...) -occur due to: -most common where: -usually happens at what range:
-due to intracranial pressure waves -most common in orbital plates -common in contact wounds (gas discharge and amount of energy)
name things that forensic professionals can determine about gunshot wounds
-entrance vs. exit -range of fire (how far was the muzzle of the weapon?) -direction of wound path -injured organs -how long did they survive/remain conscious -recovery of projectiles
what can bullet wipe help you determine
-entrance/exit -sequence of fire
things that can mimic soot (pseudo gunpowder soot)
-fingerprint dusting powder -graphite (bullet striking pencils) -asphalt (bullet striking ground) -powdered lead (bullet fragments) -dried edges of entrance wound (blood)
name common examples of pseudo gunpowder stipple
-glass -fragmented bullet -homemade silencers -post-mortem insect activity (ants and roaches) -hemorrhaging of the hair follicles -medical intervention (sutures and staples) -petechiae
types of contact gunshot wounds
-hard -loose -angled -incomplete -near
size and shape of exit wound may depend on
-location of exit wound -what it passed through first
the amount of KE lost in the tissue depends on what factors
-mass and velocity of the bullet (KE at time of impact) -angle of yaw at time of impact -type of bullet -type of tissue involved
problems that may arises from x-raying bullets
-may distort the size -aluminum bullets difficult to see -other things may mimic bullets
bone perforation depends on what
-velocity of the bullet -bullet construction -weight of bullet -angle of interaction btwn bullet and bone -type of bone
soot generally does not travel further than: ******
12 inches (1 foot)
gunpowder generally does not travel further than:
3 feet
differentiate the type of entrance wound made by bullets fired form 5, 50 or 500 feet
ALL THE SAME (distant-range)
how does one determine range for a distant-range wound
CAN'T (no gunpowder residue, no stippling, no soot)
what does a cylinder gap look like
L or V shaped black area
used on clothing; detects nitrites as orange spots used to determine range of fire
Modified Greiss Test
can you estimate caliber of a bullet by an entrance wound?
NO = skin is very elastic; it can stretch and contract so measurements do not always correspond to size of bullet
what can bullet wipe tell you about the range of the shot
NOTHING
detects lead residue around an entrance defect (i.e. from primer, bullet, residue from barrel)
Sodium Rhodizonate Test
severity of wound is directly related to the:
amount of KE lost in the tissue
symptoms of lead poisoning from retained bullets cells involved
anemia, seizures intranuclear inclusions of hepatocytes
flatter surface but the muzzle is not complete in contact with it
angled contact
bullet emboli usually occur due to what types of bullet wounds (where)
aorta/heart embolize to legs, pelvis, brain (rare) may have regurgitation or aspiration of bullets involving the oral cavity or respiratory tree
different shapes of gunpowder
ball flattened ball disk, flake
why could you see shored exit wounds in the neck
because folds of the neck can support each other
how does bone indicate direction of bullet
beveling
when/where do re-entrance wounds most commonly occur
bullet perforates arm and then enters the thorax
when oil and grease are pulled from the gun's chamber along with the bullet and deposited around entrance wound
bullet wipe
soot is vaporized:
carbon
when muzzle is away from the body at time of discharge but close enough to produce gunpowder stippling and possibly soot deposition
close range - intermediate range wounds
Gunpowder stippling at closer range and greater range
closer range = narrow, more dense pattern greater range = wider, less dense pattern
different types of gunpowder
coated grains (shiny, black) uncoated grains (green or beige)
soot and gunpowder deposition in near contact GSW
concentric circles (most concentrated around the entrance wound, then lighter and lighter as it goes outward)
what components do energy dispersive x-rays analyze for
copper, antimony, barium, lead
when you have an exit wound on the skin, does that always mean that the bullet left the body? explain how not
could be piece of bone that broke off and left the body
seen when cloth is wrapped around a revolver at the time of the shooting
cylinder gap
variation of abrasion rings from entrance wounds depends on: what are the main types of variation
depends on direction bullet entered concentric (perfect equal circles) vs. eccentric (not centered around entrance wound, off to the side, when the bullet enters at an angle)
soot and gunpowder deposition in a loose contact GSW
deposited in a BAND circumferentially around the wound
in tangential wounds, torn margins of skin (apices)point in what direction
direction where the bullet came from, point in direction the bullet moved
_______-range entrance wounds may be stellate especially over (what types of skin) what can these wounds resemble
distant-range especially over bony prominences (i.e. the head) can resemble exit or contact wounds in this case!!!
when the muzzle of the gun is far enough from the body so that no soot or gunpowder is deposited on the body
distant-range wounds
soot and gunpowder distribution in angled contact
eccentric (no real pattern) entrance wound is at the base of this eccentric distribution
soot and gunpowder disposition in incomplete contact GSW
elongated area of searing, gunpowder and soot (only on side that is lifted up partially)
analyzes the edges of an entrance wound for various components
energy dispersive x-ray
describe entrance vs. exit wounds of bone
entrance = round, oval, punched-out, sharp edges exit = excavated in cone-like manner (external beveling)
usually has a ring of abrasion (entrance or exit wound)
entrance = scraping the skin
even though a stellate entrance wound may resemble an exit wound, you can tell them apart because:
entrance wound cannot be re-approximated
entrance or exit wound (inner hole is smaller than outer hole)
exit wound
muzzle imprint in loose contact GSW
generally not present in loose contact
which travels further? soot or gp
gp
elongated area of abrasion (type of entrance wound) damage to dermis only
graze wound (just grazes the dermis)
which causes tattooing (stippling), soot or gunpowder
gunpowder only (soot is too light)
describe what a wound might look like when shot (hard contact) through clothing
gunpowder seen all over front of clothing disorganized scattering of gunpowder seen around the wound after traveling through the clothing
how can you tell the difference between actual gunpowder stipple and pseudo
gunpowder stipple is much smaller and much more uniform
when gunpowder causes injury, abrasion, burning of the skin; but it falls out and is gone (not permanent)
gunpowder stippling
when gunpowder embeds itself in the skin; may cause permanent discoloration
gunpowder tattooing
tangential wounds of the skull (they graze the bone)
gutter wounds
when skin surrounds the muzzle and creates a "muzzle stamp" = tearing of skin while it's simultaneously being blackened by soot
hard contact GSW
when the edges of the wound (skin) are seared by hot gases and blackened by soot (burning) soot and gunpowder are found within the wound track
hard contact GSW
stellate entrance wounds occur most commonly where
head
typical places that incomplete contact wounds are seen
head, shoulder, buttocks
coloration of skin during hard contact GSW
in addition to the black color from soot, the tissue surrounding the wound may have a cherry red color from *carboxyhemoglobin* (carbon monoxide release)
when/where are shored entrance wounds typically seen
in re-entrance wounds involving the arm and chest (when the arm is leaning on the body)
occurs when the body surface is not flat (i.e. the head)
incomplete contact
when a bullet passes through an object (i.e. door, window) before striking person; these objects are called:
intermediary targets
when a bullet strikes at a shallow angle, it produces a wound with one edge having characteristics of an entrance wound while the other edge has external beveling characteristic of an exit wound
keyhole wounds
how do re-entrance wounds typically present; how does it differ from the original
large, irregular wound with irregular abrasion ring (much larger and irregular compared to the original)
how do exit wounds of lax skin differ from exit wounds of tightly-stretched skin
lax skin (i.e. armpit) = can look like stab wound, slit-like tight skin = stellate
what types of bullets typically produce bullet wipe
lead and full jacketed
very rare; may occur if the lead bullet is lodged in the synovial joint, bone, or vertebral disc
lead poisoning from retained bullets, v rare
when muzzle comes in light contact with the skin
loose contact GSW
_______-velocity bullets may strike the skull, flatten out and travel subcutaneously between the scalp and skull
low
purpose of energy dispersive x-ray is to:
map out distribution of residue in a semi-quantitative manner gives approximation of range
danger of bullets striking skull at shallow angle
may cause portion of bone to penetrate the brain
penetration/perforation of ricochet bullets
may penetrate the body but do not usually perforate
soot contains
metal from primer, bullet and cartridge case
entrance wound of a ricochet bullet
much larger, irregular wounds (because tumble through the air after ricochet)
when muzzle is close to but not in actual contact with the skin; gray zone between contact and intermediate range wounds
near contact GSW
is surrounding abrasion present in exit wounds
no (rare)
can the margins be re-approximated in an entrance wound?
no bc core of tissue is lost
is there gunpowder stipple in near contact GSW
no, too close for that
parts of body where abrasion rings may be absent
palms and soles bc thick keratinized skin
differentiate penetrating vs. perforating gunshot wounds
penetrating = projectile still in body perforating = exits the body
what color does lead turn in Sodium Rhodizonate Test what does this test tell you about range what test comes first: this or Greiss test?
pink NOTHING (must be performed after the Greiss test)
punctate abrasions produced by objects other than gunpowder; can mimic gunpowder stipple
pseudo gunpowder stipple
in a near contact (not touching) angled wound, where does soot go?
radiates outward from the muzzle; bulk of it is on same side as the muzzle; entrance wound is at the apex of the soot pattern (OPPOSITE angled contact in which the entrance wound is at the base of the pattern)
do you see bullet wipe on skin
rarely because the skin has so many oils itself that it doesn't rub off as well as on clothes
when a bullet passes through one body part and enters again in another body part
re-entrance wounds
cylinder gaps are present in:
revolvers only
describe the general shape of an entrance wound
round, oval, elliptical
results when skin is supported by a surface when bullet exits (like if person has on a tight jacket or if they are standing against a wall, or if they are laying on the ground)
shored exit wound
why do _______ exit wounds present with abrasion
shored exit wounds skin hitting against whatever the surface is; causes trauma to the skin
what can bullet wipe tell you about entrance vs. exit
shows up on entrance only
what does a shored exit wound look like
skin surrounding the wound has a broad area of abrasion (which is typically absent in exit wounds)
bullet emboli are usually caused by what type of caliber/bullet
small caliber low velocity bullets
is gunpowder smokey or smoke-less
smokeless
vaporized carbon
soot
what can and cannot be wiped away
soot can be wiped away gunpowder stippling cannot
compare how far you can receive deposition of soot and gunpowder stipple
soot from handguns will not deposit beyond 12 inches (1 foot) gunpowder stippling from handguns does not generally occur beyond 3 feet
bullet wipe is composed of
soot, lubricant, metallic elements
what is lighter, soot or gp? can soot be wiped away?
soot. yes, it wont be embedded in the skin like GP
typical wound shape from hard contact GSW
stellate (gases expanding outward) may have muzzle imprint
injury into subcutaneous tissue; area of abrasion at the entrance, torn margins of skin; deeper than a graze wound but does not enter the body
tangential wound
severity of wound is determined by:
the size of the temporary cavity it creates
what does bullet wipe look like and where is it seen
thin, grey, greasy stain around the bullet hole (entrance wound only, especially on clothing)
common shape of exit wounds
various and irregular
radiating fractures in bone can tell you a lot about:
what bullet came first (bullet holes that produce later radiating fractures will NOT cross the original bullet's radiating fracture lines)
what does the entrance wound look like after passing through intermediary targets
yaw of bullet increases, producing an atypical entrance wound; deformation of bullet may also contribute to this can also cause more than one entrance wound if fragmentation occurs
are microtears present in entrance wounds?
yes = especially in high velocity (i.e. rifles)
can margins of exit wound be re-approximated
yes bc tissue is not lost
what measurements can be determined by measuring the cylinder gap
you can determine the barrel length by measuring the distance between entrance defect (bullet hole) and cylinder gap
