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Forensic medicine > Gunshot wounds and ballistics > Flashcards

Gunshot wounds and ballistics Flashcards

1
Q

Interior ballistics (travel within the weapon) can give you what information?

A 
Rifling marks on bullet - class characteristics (make model), individual characteristics (unique to gun). 
cartridge case (extractor)
primer cap (firing pin)
fingerprints
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2
Q

if the mass of the bullet is doubled, the energy is doubled - true or false

A

true

KE = 0.5mass x velocity2

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3
Q

If the velocity of the bullet is doubled, the kinetic energy is doubled - true or false

A

false - double velocity - quadrupled energy

KE = 0.5mass x velocity2

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4
Q

Which rifling marks indicate the class characteristics of the weapon?

A 
No. of lands and grooves
width
depth
degree of twist
direction of twist
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5
Q

Which rifling marks indicate the individual characteristics of the weapon?

A

imperfections on lands & grooves due to firing/use

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6
Q

Describe the components of small arms ammunition.

A

Bullet - lead alloyed with tin and/or antimony.
Propellant - smokeless powder which burns to produce large volume of gas under pressure. This forces the bullet down and out the barrel.
Primer - shock-sensitive chemical compound which explodes on impact by firing pin, flame secondarily ignites propellant. Primer chemic compounds (lead, barium, antimony) can be found on shooter.
Cartridge case - filled with propellant, expands to fill chamber on discharge

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7
Q

Jacketed bullets are encased in CuZn, CuNi or Al - why?

A

prevents the bullet from fragmenting, used in auto-loading pistols and high-velocity rifles.

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8
Q

List the wounding mechanisms of gunshots.

A

Direct laceration
Shockwaves - may rupture gas-filled organ
Secondary projectiles - e.g. shattered bone.
Discharge gases (contact range)

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9
Q

Entry wound will have inverted skin margin and exit wound shows everting skin margins - true or false

A

true

exit wound is bigger, since skin everts there are no abrasions at exit site

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10
Q

List some skin surface signs of a gunshot

A

muzzle imprint (skin kick-back into gun)
Singeing (hot gases)
Smudging/soot
Tattooing (propellant)

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11
Q

Sideways escape of soot-laden gas indicates angled contact range - true or false

A

false - indicates loose contact range

angled contact range - eccentric soot stain

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12
Q

muzzle against skin = which range of gunshot and what will you see?

A

muzzle against skin = contact range

soot and propellant seared into margins

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13
Q

anything from contact to intermediate range = ?

A

near-contact range

few cm

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14
Q

tattooing and peripheral ring of soot staining is seen in near-contact range - true or false

A

false - NO tattooing but peripheral ring of soot staining can reach up to 20-30cm
soot can be wiped off!

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15
Q

gunshot within arm’s reach = ?

A 
intermediate range (still near enough to be suicide)
few cm to 1cm
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16
Q

powder tattooing signifies which range?

A

intermediate range individual reddish-brown punctate abrasions and/or vital reaction (rim of bruising)

17
Q

further than arm’s length = ? range

A

distant range

>1m

18
Q

at distant range, which skin features will you see?

A 
no flame effects
no soot effects
no propellant tattooing
bullet is on its own.
entry wound (central laceration) with marginal abrasion
19
Q

an elliptical laceration with marginal abrasion, with no soot, flame or propellant effects indicates what?

A

a shot from distant range (>1m) impacting at an angle other than a right angle

20
Q

entry wound is circular and exit wound is irregular - true or false

A

true

diameter bullet on exit

21
Q

exit wounds have a marginal abrasion - true or false

A

false - no abrasion on exit; marginal abrasion on entry

No abrasion UNLESS skin pushed against hard surface on exit (bra strap)

22
Q

entry wound at temple which has extended open the laceration, no tattooing, soot/flame marks around margins

A

contact range - split by gases

23
Q

gunshot residues deposit on ulnar side of firing hand - true or false

A

false - radial side of firing hand

24
Q

what are gunshot residues made up of?

A

generally composed of one, two or three of the elements present within the primer.

25
Q

the bigger the shotgun gauge, the more lead balls within the barrel for 1lb weight - true or false

A

false
the bigger the gauge = smaller no. of balls in that barrel for 1lb weight

e.g. 20 gauge = 15mm internal diameter
12 gauge = 18.2mm diameter

26
Q

a shotgun power piston will contribute to the wound <20 feet range - true or false

A

true - shotgun power piston will strike body at <20’

<1ft, not yet opened
1-3ft, abrasions from petals
>3ft, folded back
>8-10ft, strikes alongside entry

27
Q

what can the shotgun power piston indicate?

A

manufacturer and gauge

28
Q

A contact range, suicidal shotgun wound to the head is very mutilating due to the gas (comminuted #) and energy of the shot (brains exit via #)… but which side of body gets brunt of shot?

A

if right-handed, left side gets brunt of shot since torso rotates.

This can be confirmed by fine mist/spray of blood onto hand / neighbouring objects which result from the HV shot.

29
Q

a cherry pink wound margin is seen in which range of shotgun shot?

A

contact range shotgun wound to torso

carbon monoxide causes the cherry pink colour

30
Q

contact range shotgun leaves which skin features?

A 
circular entry = muzzle diameter
muzzle imprint
soot smudging
burning or melting of clothes since all the soot, propellant and flame with be caught on clothes
cherry pink wound margin (CO)
31
Q

Which range of shotgun wound causes scalloped margins?

A

shotgun wound distant range causes scalloped margins by 3 feet
no tattooing >3’

32
Q

Which range of shotgun wound causes satellite holes?

A

shotgun wound distant range causes satellite holes (fliers) by 4’

cuff of satellite holes by 6’

33
Q

a loose near-contact gunshot wound shows soot staining on skin. When the soot is wiped away, a burnt hole left = distance?

A

<3-6’ since flame reached skin

34
Q

petal marks from power piston = ?

A

1-3ft = abrasions from petals

<1ft = not yet opened, >3ft folded back

35
Q

half-formed cuff of satellite holes = ?

A

~5’ since cuff beginning to form

start to form at 4’ and full cuff by 6’

36
Q

signs indicative of gunshot suicide include…?

A

male > females
contact range wound
HV blood splatter on steadying hand
GS residues on firing hand

37
Q

smudging

A

deposition of soot on skin (production of gun discharge)

38
Q

tattooing

A

propellant grains abrading and embedding themselves into the skin

39
Q

singeing

A

burning of the skin and its hairs from hot gases including flame

Forensic medicine (10 decks)

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