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