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Forensic medicine > Bodies from fire > Flashcards

Bodies from fire Flashcards

1
Q

what is “flashover”?

A

ignition temperature of nearby combustible material is reached (sinister development in a housefire).

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2
Q

List the 3 main aspects of fire dynamics.

A

Incipient - fuel supply heated, ready to burn.
Emergent smouldering - inefficient combustion: smoke ++
Growth of flames - efficient burning, intensity doubles for each 10 degree C rise in temp. flashover.

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3
Q

what is the most common manner of death in bodies from fires?

A

accident - alcohol, drugs, cigarettes implicated.

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4
Q

homicide is a rare manner of death in bodies from fires - true or false

A

true - rare as method except arson or concealment of homicides (often fails).

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5
Q

What are the 4 main questions to ask when investigating fire-related deaths?

A

Was the victim alive at the start of the fire?
what was the CoD? (fire / other)
Why was the victim in the fire?
Why was the victim unable to escape?

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6
Q

Re. identification of body from fire, which personal effects often survive and where?

A

jewellery and wallets often survive

clothing can persist in flexor areas and around neck

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7
Q

It is rare to have enough DNA to identify a body from fire - true or false?

A

false - it is rare for not enough tissue to be present for DNA analysis

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8
Q

A tooth which is present in life but absent in death is an incompatible difference - true or false

A

false - tooth present in life but absent in death = compatible difference.
incompatible would be a tooth absent in life but present in death.

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9
Q

which organs/structures tend to avoid putrefaction and destruction?

A

ovaries and uterus

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10
Q

what can a fire investigator tell you about the scene of the fire?

A

the origin, development and nature of the fire

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11
Q

effects of fire continue after death - true or false

A

true

fire artefacts occur in any body from fire, irrespective of CoD

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12
Q

flexor muscles contract/drawn in = ?

HINT: aka. boxer’s position

A

pugilistic posture

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13
Q

describe PM burning

A

thin reddened margin
leathery brown from smouldering heat
charred by high temperature or direct flame
severe: skin splits and is lost; muscle loss; limb amputation

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14
Q

what colour does hair turn from singeing?

A

red/brown discolouration

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15
Q

why is skin splitting clearly a PM artefact and not something that happened AM?

A

skin is charcoaled then splits, but muscle and subcutaneous fat is exposed without being covered in soot

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16
Q

where are some common sites for skin splitting?

A

axillae, across forearms, at elbow, groin, behind knees

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17
Q

describe how a heat haematoma forms in the skull.

A

dural membranes and brain contract - blood within cranium is forced extra-durally

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18
Q

a subdural haematoma is seen on PM of a body from fire - how can you tell if this is a genuine or heat haematoma?

A

genuine haematoma will be associated with a AM fracture = genuine trauma

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19
Q

What signs suggest the victim was breathing (but not necessarily conscious) during the fire?

A

soot in airways BELOW level of vocal folds
thermal injury to the larynx
blood CO >10% (cyanide)

absence of these signs DOES NOT indicate already dead - unconscious?

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20
Q

In a fire-related death, what sign is known as ‘heat shock’?

A

thermal injury to the URT - due to smoke inhalation

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21
Q

thermal injury to the face and whole respiratory tract is common in fire-related deaths - true or false

A

false - thermal injury to face and URT is common… URT has very efficient heat exchange but LRT is protected!

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22
Q

What is the mechanism of death in heat shock?

A

dry air >150C or moist air (lower temp) -> laryngeal injury
reflex vagal inhibition from breathing hot air -> laryngeal spasm + oedema
tracheobronchial necrosis seen microscopically
rapid, immediate and early death due to inhalation of hot gases

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23
Q

What gross appearance suggests heat shock?

A

red, congested trachea which is less affected further down larynx since heat transfer is less efficient

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24
Q

At which % of Hb is carbon monoxide fatal and what level indicates victim was alive (breathing) during fire?

A

50% = fatal (>30% if heart & lung disease)

>10% indicates victim alive/breathing during fire

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25
Q

CO kills in seconds - true or false

A

false - CO kills over mins rather than sec

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26
Q

What factors effect CO toxicity?

A

Rate of inhalation
Physical activity - as O2 is consumed, requirement increases, CO bound to Hb -> worsening condition.
Individual susceptibility (heart/lung disease; higher resting HbCO)

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27
Q

At which % Hb does CO impair judgement and cause LOC?

A

30-40% Hb -> impaired judgement, LOC and failure to escape.

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28
Q

CO <10% Hb = victim was already dead

A

CO <10% does not mean already dead:
A well-ventilated fire will have enough O2 -> CO2 -> little or no CO produced (<10%)
Rapid deaths = not enough time to inhale CO

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29
Q

what is direct particulate injury in fire-related deaths?

A

super-heated soot and other particulate debris pass deeper into URT than gases
depth of penetration depends on size - smaller particles can reach alveoli

30
Q

smoke poisoning is incapacitation due to CO and other noxious gases. one of these gases is hydrogen cyanide - burning of which materials forms this gas?

A

wool, silk, nylon, polyurethanes -> hydrogen cyanide gas

31
Q

smoke poisoning is incapacitation due to CO and other noxious gases. one of these gases is benzene - burning of which materials forms this gas?

A

petroleum, plastics and polystyrene -> benzene gas

32
Q

smoke poisoning is a common CoD in fire-related deaths - true or false

A

FALSE
noxious gases cause incapacitation but RARELY DEATH
the effects can be additive meaning that non-fatal levels of multiple gases in combination may kill

33
Q

1st degree burn = ?

A

superficial

34
Q

2nd degree burn = ?

A

partial skin thickness

35
Q

3rd degree burn = ?

A

full skin thickness

36
Q

(4th degree burn = ?)

A

full skin - through fat, down to muscle and tendon

technically only 3 degrees of burning

37
Q

List the exposures which would cause 1st degree burn.

A

Brief exposure to high intensity heat
OR
long exposure to low intensity heat (sunburn)

38
Q

1st degree burns will peel and heal in 5-10 days w/o scarring - true or false

A

true

redness, swelling and pain last 48-72hrs

39
Q

Which symptom tells you that a 2nd degree burn involves deep proportion of dermis?

A

if it is painless = nerves damaged and deep
vs
superficial and painful

40
Q

2nd degree burns heal without a scar - true or false

A

TRICK Q
superficial 2nd degree - blisters and heals in 7-14 days, no scar
deep 2nd degree - blisters, painless, heals slowly but WITH scar.

41
Q

3rd degree burns are extremely painful - true or false

A

FALSE

3rd degree burns involve epidermis, dermis and underlying tissue - nerves are destroyed = painless!

42
Q

Why are tissues waxy in 3rd degree burns?

A

heat damage to vessels leaves tissues avascular and waxy - will require grafting if person survives

43
Q

a keyhole-shaped burn in a child is caused by ?

A

a cigarette burn = wider at bottom with tail = keyhole

44
Q

What is the “rule of nines” an how is it used to judge burning extent?

A 
Head: 9%
Front of torso: 18%
Back of torso: 18%
EACH arm: 9%
EACH leg: 18%
Victim's palm: 1%

If >50% if burnt = poor prognosis
(<50% in elderly)

45
Q

What are some burns complications that occur within the first 48hrs of injury?

A

fluid loss
hypovolaemia
shock
renal failure

46
Q

What are some burns complications that occur 2-6 days after injury?

A 
burn oedema
ischaemia
conversion
airway oedema
respiratory failure
47
Q

Surgical escharotomy needs to be done in which kind of fires/burns and what is its purpose?

A

In accelerated clothing fires, areas of skin under clothes are burnt more than uncovered skin.
Surgical escharotomy allows skin to relax and not squeeze arteries.
(similar idea to fasciotomy)

48
Q

What is “cindering”?

A

cindering is the white appearance of bone after severe burning

49
Q

a natural death with PM burning is sometimes known as…?

A

spontaneous human combustion!
person dies and cigarette ignites clothes which acts as wick and body fat as fuel.
fire damage localised to body and surroundings

50
Q

Cremation leaves 1-1.5kg of white calculated bone and ash behind - which bone parts are left behind?

A

ends of long bones
skull fragments
pelvic fragments

51
Q

In which conditions do scalds occur?

A

moist heat - steam or hot liquids

52
Q

a scald resembles a 3rd degree burn - true or false

A

false - scalds resemble 1st or 2nd degree burns

53
Q

Describe the appearance of a scald.

A

red, swollen, blistered, painful
well demarcated
no singeing, charring or carbonisation

54
Q

What patterns are seen in scald injuries?

A 
Clothing spares areas
Flow pattern: gravity & cooling
Splash (irregular): thrown 
Glove & stocking: dipping hands and feet
Doughnut: sitting in bath (sparing of contact areas, buttocks/knees)
55
Q

What factors effect tissue damage in electrical injuries?

A 
Voltage applied
Resistance of skin (wet/dry)
Resistance of tissues (muscles designed to propagate currents)
Current which flows
Duration of contact (deep burning)
56
Q

dry skin has high resistance to current flow - true or false

A

true

57
Q

Where are the vital areas in fatal electrocution?

A

Hand-opposite foot = across chest (heart: VF)
Across chest = respiratory muscle paralysis
Through head = cardiac/resp. centres in brain stem

58
Q

The current in domestic electricity sockets is 240V, 50Hz alternating current. It causes VF and arrest as well as ? effect on muscles.

A

spasm of hand and forearm muscles causes spasm and “hold on”

prolonged contact causes burning which continues PM

59
Q

“higher voltage - throws away

lower (domestic) voltage - …”

A

higher voltage - throws away

lower (domestic) voltage - “hold on”

60
Q

there is often a clear mark signifying an electrical injury - true or false

A

false - often no visible mark

especially when there is a broad area of contact and skin is moist or sweaty

61
Q

How can you determine entry and exit site of an electrical current causing injury?

A

burn at entry site (often hands) and at exit site (often feet)
keratin burned = brown discolouration

62
Q

Describe the cutaneous lesion seen from firm contact with an electrical current.

A

collapsed blister, surrounding zone of erythema, peripheral ring of pallor (target shaped lesion)
metallisation of skin (e.g. copper wire embedded in skin)

63
Q

Describe the cutaneous lesion seen from loose contact with an electrical current.

A

sparks leap gap between source and entry - multiple spark lesions form HV (crocodile skin)
melts epidermal keratin which cools to form a localised hard brown nodule
clothes may ignite

64
Q

Person found dead outside after a storm. They look like they have been electrocuted - what signs would point to a lightening strike as CoD?

A

Clothing scorched and torn by blast
skin burns near metal objects (jewellery, buttons/zips)
arborescent markings - red

scene: near a crane / tall metal structure or near trees/other tall structures

65
Q

acid burns cause coagulative necrosis - true or false

A

true - acids with pH <2 produce coagulative necrosis

66
Q

Chemical burn from acids will scab over. The colour of the scab depends on chemical used. What colour is the scab from nitric acid burns?

A

nitric acid - yellow/brown scab

67
Q

Chemical burn from acids will scab over. The colour of the scab depends on chemical used. What colour is the scab from hydrochloric acid burns?

A

hydrochloric acid - white/grey scab

68
Q

Alkaline burns cause coagulative necrosis - true or false

A

false - alkalis with pH >11.5 cause liquefactive necrosis

69
Q

which chemical burn penetrates more deeply (acid/alkali)?

A

alkali

70
Q

Describe the appearance of a burn from caustic soda (NaOH).

A

grey-white mucoid burn

Forensic medicine (10 decks)

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