Bodies from fire Flashcards
what is “flashover”?
ignition temperature of nearby combustible material is reached (sinister development in a housefire).
List the 3 main aspects of fire dynamics.
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.
what is the most common manner of death in bodies from fires?
accident - alcohol, drugs, cigarettes implicated.
homicide is a rare manner of death in bodies from fires - true or false
true - rare as method except arson or concealment of homicides (often fails).
What are the 4 main questions to ask when investigating fire-related deaths?
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?
Re. identification of body from fire, which personal effects often survive and where?
jewellery and wallets often survive
clothing can persist in flexor areas and around neck
It is rare to have enough DNA to identify a body from fire - true or false?
false - it is rare for not enough tissue to be present for DNA analysis
A tooth which is present in life but absent in death is an incompatible difference - true or false
false - tooth present in life but absent in death = compatible difference.
incompatible would be a tooth absent in life but present in death.
which organs/structures tend to avoid putrefaction and destruction?
ovaries and uterus
what can a fire investigator tell you about the scene of the fire?
the origin, development and nature of the fire
effects of fire continue after death - true or false
true
fire artefacts occur in any body from fire, irrespective of CoD
flexor muscles contract/drawn in = ?
HINT: aka. boxer’s position
pugilistic posture
describe PM burning
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
what colour does hair turn from singeing?
red/brown discolouration
why is skin splitting clearly a PM artefact and not something that happened AM?
skin is charcoaled then splits, but muscle and subcutaneous fat is exposed without being covered in soot
where are some common sites for skin splitting?
axillae, across forearms, at elbow, groin, behind knees
describe how a heat haematoma forms in the skull.
dural membranes and brain contract - blood within cranium is forced extra-durally
a subdural haematoma is seen on PM of a body from fire - how can you tell if this is a genuine or heat haematoma?
genuine haematoma will be associated with a AM fracture = genuine trauma
What signs suggest the victim was breathing (but not necessarily conscious) during the fire?
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?
In a fire-related death, what sign is known as ‘heat shock’?
thermal injury to the URT - due to smoke inhalation
thermal injury to the face and whole respiratory tract is common in fire-related deaths - true or false
false - thermal injury to face and URT is common… URT has very efficient heat exchange but LRT is protected!
What is the mechanism of death in heat shock?
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
What gross appearance suggests heat shock?
red, congested trachea which is less affected further down larynx since heat transfer is less efficient
At which % of Hb is carbon monoxide fatal and what level indicates victim was alive (breathing) during fire?
50% = fatal (>30% if heart & lung disease)
>10% indicates victim alive/breathing during fire
CO kills in seconds - true or false
false - CO kills over mins rather than sec
What factors effect CO toxicity?
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)
At which % Hb does CO impair judgement and cause LOC?
30-40% Hb -> impaired judgement, LOC and failure to escape.
CO <10% Hb = victim was already dead
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
what is direct particulate injury in fire-related deaths?
super-heated soot and other particulate debris pass deeper into URT than gases
depth of penetration depends on size - smaller particles can reach alveoli
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?
wool, silk, nylon, polyurethanes -> hydrogen cyanide gas
smoke poisoning is incapacitation due to CO and other noxious gases. one of these gases is benzene - burning of which materials forms this gas?
petroleum, plastics and polystyrene -> benzene gas
smoke poisoning is a common CoD in fire-related deaths - true or false
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
1st degree burn = ?
superficial
2nd degree burn = ?
partial skin thickness
3rd degree burn = ?
full skin thickness
(4th degree burn = ?)
full skin - through fat, down to muscle and tendon
technically only 3 degrees of burning
List the exposures which would cause 1st degree burn.
Brief exposure to high intensity heat
OR
long exposure to low intensity heat (sunburn)
1st degree burns will peel and heal in 5-10 days w/o scarring - true or false
true
redness, swelling and pain last 48-72hrs
Which symptom tells you that a 2nd degree burn involves deep proportion of dermis?
if it is painless = nerves damaged and deep
vs
superficial and painful
2nd degree burns heal without a scar - true or false
TRICK Q
superficial 2nd degree - blisters and heals in 7-14 days, no scar
deep 2nd degree - blisters, painless, heals slowly but WITH scar.
3rd degree burns are extremely painful - true or false
FALSE
3rd degree burns involve epidermis, dermis and underlying tissue - nerves are destroyed = painless!
Why are tissues waxy in 3rd degree burns?
heat damage to vessels leaves tissues avascular and waxy - will require grafting if person survives
a keyhole-shaped burn in a child is caused by ?
a cigarette burn = wider at bottom with tail = keyhole
What is the “rule of nines” an how is it used to judge burning extent?
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)
What are some burns complications that occur within the first 48hrs of injury?
fluid loss
hypovolaemia
shock
renal failure
What are some burns complications that occur 2-6 days after injury?
burn oedema ischaemia conversion airway oedema respiratory failure
Surgical escharotomy needs to be done in which kind of fires/burns and what is its purpose?
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)
What is “cindering”?
cindering is the white appearance of bone after severe burning
a natural death with PM burning is sometimes known as…?
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
Cremation leaves 1-1.5kg of white calculated bone and ash behind - which bone parts are left behind?
ends of long bones
skull fragments
pelvic fragments
In which conditions do scalds occur?
moist heat - steam or hot liquids
a scald resembles a 3rd degree burn - true or false
false - scalds resemble 1st or 2nd degree burns
Describe the appearance of a scald.
red, swollen, blistered, painful
well demarcated
no singeing, charring or carbonisation
What patterns are seen in scald injuries?
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)
What factors effect tissue damage in electrical injuries?
Voltage applied Resistance of skin (wet/dry) Resistance of tissues (muscles designed to propagate currents) Current which flows Duration of contact (deep burning)
dry skin has high resistance to current flow - true or false
true
Where are the vital areas in fatal electrocution?
Hand-opposite foot = across chest (heart: VF)
Across chest = respiratory muscle paralysis
Through head = cardiac/resp. centres in brain stem
The current in domestic electricity sockets is 240V, 50Hz alternating current. It causes VF and arrest as well as ? effect on muscles.
spasm of hand and forearm muscles causes spasm and “hold on”
prolonged contact causes burning which continues PM
“higher voltage - throws away
lower (domestic) voltage - …”
higher voltage - throws away
lower (domestic) voltage - “hold on”
there is often a clear mark signifying an electrical injury - true or false
false - often no visible mark
especially when there is a broad area of contact and skin is moist or sweaty
How can you determine entry and exit site of an electrical current causing injury?
burn at entry site (often hands) and at exit site (often feet)
keratin burned = brown discolouration
Describe the cutaneous lesion seen from firm contact with an electrical current.
collapsed blister, surrounding zone of erythema, peripheral ring of pallor (target shaped lesion)
metallisation of skin (e.g. copper wire embedded in skin)
Describe the cutaneous lesion seen from loose contact with an electrical current.
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
Person found dead outside after a storm. They look like they have been electrocuted - what signs would point to a lightening strike as CoD?
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
acid burns cause coagulative necrosis - true or false
true - acids with pH <2 produce coagulative necrosis
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?
nitric acid - yellow/brown scab
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?
hydrochloric acid - white/grey scab
Alkaline burns cause coagulative necrosis - true or false
false - alkalis with pH >11.5 cause liquefactive necrosis
which chemical burn penetrates more deeply (acid/alkali)?
alkali
Describe the appearance of a burn from caustic soda (NaOH).
grey-white mucoid burn
