Bodies from Fire Flashcards
What are the 3 components of a fire
Oxygen
Heat
Fuel
All are required for a fire to propagate and burn
If any run out the fire will stop
List the phases of a fire
Incipient
Emergent smoldering
Growth of flames
Describe the incipient phase of a fire
This is when the fuel source is heated and becomes ready to burn
Start of the fire
Describe the emergent smoldering phase of a fire
There is inefficient combustion which leads to lots of smoke production
Low level burn - no flame but lots of smoke
Describe the flame growth phase of a fire
The burning is efficient - flames start to grow
The intensity of the flames doubles for every 10’C rise in temperature
Flashover occurs as the ignition temperature of surrounding materials is reached (more like an explosion)
Everything will start burning at this point
What is the cause of most fires
Accidents
Electrical malfunction, cigarettes, intoxication etc
Clothing may also catch fire
How might someone commit suicide by fire
Pour accelerate on clothes and light it
Or douse car with petrol and lighting it
Very rare in the West (may be seen in asian culture)
List the potential manner of death in a body from fire case
Natural - it can prevent them escaping (e.g. they’ve collapsed)
Accidental - cigarettes, intoxication, electrical fires etc
Suicide
Homicide
Fire is a common method of homicide = true or false
False
It is rare as the actual method
Unless someone dies in a deliberate arson case
More commonly used to try and conceal the body but often fails (fire not CoD but may hide another cause)
Through which mechanisms can the fire itself cause death
Carbon monoxide poisoning
Smoke inhalation
Burns
Heat shock
What 4 questions must you answer when investigating a body from fire
Was the victim alive at the start of the fire?
What was the cause of death?n (fire itself or other)
Why was the victim in the fire?
Why was the victim unable to escape?
The cause of death in a body from fire isn’t always due to the fire itself, what other causes are there
May have been a natural death and then the location caught fire
May be due to alcohol or drugs
May be a homicide that is being concealed - must consider this
How can you identify a body from fire
Circumstances - who was supposed to be in building at that time
Personal effects - jewelry or wallets on body may survive and can be identifiable
Fingerprints - actually rare for these to be destroyed completely
DNA - can be taken from tissue
Dental - match teeth to AM dental records (often the go-to)
X-Rays - match to medical history/ AM x-rays
Operations - identifiable devices, missing organs, pins/plates etc.
How can a prostheses or medical device help identify a body from fire
Can match the device to the person
Basic = the suspected victim has a knee replacement and you find a prosthetic joint (can match shape/size)
More specifically = most devices/prosthesis will have serial numbers which should be recorded in surgical notes (this can confirm ID)
What investigation are carried out on a body from fire
Medical history
Circumstances
Fire investigator’s examination of scene (origin, development, nature of fire such as heat and toxins produced)
Autopsy - full exam
Toxicology & laboratory investigations - samples taken at autopsy
What are fire artifacts
Damage to the body that occurs regardless of whether the person was alive or dead at the time (irrespective of CoD)
The effects of the fire continue after death
List common fire artifacts
Pugilistic posture - boxer Post mortem burning Hair singed & turns reddish-brown Skin becomes blistered or may shrink, tighten & split Heat fractures Heat haematoma -common in head Damage from falling masonry Damage can be done during recovery of the body
List the features of PM burning
Thin reddened margin
Leathery brown, dry skin from smoldering heat
Tissue can be charred by high temp or direct flame
In severe cases the skin splits and is lost
This can progress to muscle loss, amputation of limbs (as tissues burn and bones fracture/disintegrate) and exposure of the body cavities
What is the pugilistic posture
A position commonly assumed by corpses after fire exposure
The flexor muscles contract and the body curls up (arms up, hands in fists, bent legs and bent at hips)
Looks like a boxer pose
Which signs tell you that the victim was breathing during the fire (not necessarily conscious)
Soot in airways below the level of vocal folds - has to have been inhaled to reach these levels
Thermal injury to larynx
Blood CO > 10%
Absence of soot below vocal folds, thermal larynx injury etc means the victim was already dead in the fire - true or false
False
Not necessarily - may have been a quick death so haven’t had time to inhale the smoke/CO etc
How can smoke inhalation cause death
Thermal injury to URT (heat shock = rapid death)
CO poisoning
Direct particulate injury (ash and debris)
Smoke poisoning due to release of toxic gases as things burn
What is carbon monoxide and why would you find in in bodies from fire
A colourless, odourless gas (silent killer)
Most potent of gases in smoke
It is released due to incomplete combustion of fuels
Fatal levels are found in victims from 50% of fatal house fires
Describe the mechanism of death following thermal injury to the URT
Breathing hot air may cause reflex vagal inhibition - lots of nerves in the URT
This will cause a very rapid death - within seconds
Thermal injury can cause laryngeal spasm and/or laryngeal oedema (fluid accumulation = swelling and occlusion)
The URT is very efficient at heat exchange - true or false
True
The LRT is relatively protected from thermal injury so rare to get heat damage
Thermal injury is common in which parts of the body
Face
URT
What air temperature is required to cause laryngeal injury
Dry air >150’C or moist air
How do you estimate CO levels in a body
Measure it’s concentration in the blood
Blood levels expressed as % of Hb that exists as COHb
Clinical effects are dose dependent
What % of Hb is considered a fatal dose of CO
50% and over
May be lower in the presence of existing heart/lung disease
A CO % of over 10% indicates what in a body from fire
That the victim was alive (breathing) during the fire
How does CO inhalation cause poisoning
It causes chemical poisoning of bloodstream
It binds to Hb in the blood which diminishes it’s O2 carrying capacity - CO binds in it’s place
It’s affinity for Hb is 200x greater than that of oxygen
Less O2 at tissues
What determines CO toxicity
Rate of inhalation (conc of CO, duration of exposure) Physical activity (e.g. trying to escape) - increases O2 demand so effect felt quicker Individual susceptibility (heart, lung disease increases risk)
Describe the symptoms of CO poisoning
at different concentrations
20-30%: dizziness, SOB, headache, nausea, fatigue
May be seen in chronic exposure such as faulty heater
30-40%: impaired judgement, failure to escape, loss of consciousness
50%: generally accepted as fatal level
Why might someone have a CO concentration of under 10% in day to day life
May actually have a standard level of around 5% in life
HIgher in smokers
Also seen in city dwellers
If a body from fire has a CO concentration under 10% it means they were already dead in the fire - true or false
False
This may be seen if there was little or no CO produced in the fire (if there was abundant O2 as CO2 is made instead )
Or if death was rapid such as in heat shock
The victim wont have inhaled enough to raise levels
CO poisoning in a body from fire is associated with what other fire effect
Soot inhalation
Soot and CO both present in smoke so both usually present
How common is CO poisoning among building fire victims
85% show CO poisoning
50% have fatal levels
What is the classic sign of CO poisoning at autopsy
Cherry red/pink discolouration of the body
Seen in lividity and in the eyes externally
Even internal structures like muscles can be pink
What is the histological sign of thermal laryngeal injury
Tracheobronchial necrosis seen microscopically
May see some haemorrhage and inflammation in the larynx - due to lining damage from hot gas
How do particulates cause injury in fires
Superheated soot & other particulate debris passes deeper into URT than gases and cause injury
What determines particulate penetration
The size of the particulate The smaller they are the deeper they can go >10 um: to nares (nose) 5-7 um: to trachea & bronchi 1-3 um: reach alveoli
What effect does smoke poisoning typically have on a fire victim
Gases cause incapacitation but rarely death
Which gases cause smoke poisoning
CO, cyanide, HCl, nitrous oxide, aldehydes, benxene, ammonia, sulphur dioxide, phenol, Acrolein
The gas released is dependent on the fuel source
CO and cyanide are the main ones measured
Which fuels release CO2 when burnt
All combustibles containing carbon
May also release CO
Which fuels release NO2 when burnt
Cellulose
Polyurethanes
Acrylnitrile
Which fuels release HCl when burnt
PVC
Which fuels release hydrogen cyanide when burnt
Wool
Silk
Nylons
Polyurethanes
Which fuels release aldehydes when burnt
Wool Cotton Paper Plasters Wood Nylon Polyester resin
Which fuels release benzene when burnt
Petroleum
Plastics
Polystyrene
Which fuels release ammonia when burnt
Melamine
Nylon
What are the main burns classifications
First degree - superficial
Second degree- partial skin thickness
Third degree - full skin thickness
Fourth Degree - through fat, down to muscle & tendon
What causes a first degree burn
Brief exposure to high intensity heat (flame)
or
Long exposure to low intensity heat - e.g. sunburn
Describe a first degree burn
Involves epidermis only (vessels, nerves etc are protected)
Will have redness, pain and swelling for 48-72hrs
Peels then heals in 5-10 days
No scarring - damage to skin is slight
Describe a second degree burn
Involves epidermis and a variable proportion of the underlying dermis (can affect vessels, nerves, follicles etc)
If it’s relatively superficial you get pain and blistering but it heals in 7-14 days
If deeper it is painless but healing is slow and will scar
May require grafting
Will cause fluid loss and metabolic imbalance
Why are deep burns painless
The burn goes deep enough to destroy the nerve fibers so you cannot feel it anymore
Describe a third degree burn
Involves epidermis, dermis & underlying tissue
Not painful - destroys nerves and vessels
Tissue becomes avascular and waxy as heat damages vessels (secondary damage from ischaemia)
Will cause fluid and metabolic imbalances
Will require grafting if survived - skin unable to regenerate as it has been lost
May be fatal
List common accidental causes of burns in children
Hot water scalds
Fires (open fire, electric & gas fire)
Clothing can catch fire
Usually a single event/burn
List common deliberate causes of burns in children
Cigarette burns - typically in areas covered by clothing
Scalding
Hot objects (iron)
Sign of abuse - especially if multiple
How do you express the extent of a burn
You express it as a % of the total body
Use rule of 9’s - body split into 9% regions
Head, each arm - 9%
Front torso, back and each leg = 18% (2x9%)
The victims palm size is roughly 1% of body so can use this
What burn percentage has a poor prognosis
Anything over 50%
Lower in the elderly
Which complications of burns occur in the first 48hrs
Fluid loss
Hypovolaemia - due to fluid loss
Shock
Renal failure
Which complications of burns occur after 2-6 days
Burn oedema Ischaemia - due to blood vessel damage Conversion - 1st can become 2nd degree following these secondary effects Airway oedema Respiratory failure
Which complications of burns occur after 7 days or more
Infection
Tourniquet effect
What is a surgical escharotomy
The skin is deliberately incised to release pressure from the tourniquet effect of the burn
Allows blood to flow back into the area
What is a flash fire
A very brief, high intensity fire that is lethal
Has an explosive ignition - use up all the O2 quickly
May travel in a particular direction such as in a blast
Very high temperatures - 500-9500’C
Hydrocarbon vapors evaporate and it also produces soot, CO and toxic gases
What is the true cause of spontaneous human combustion
Typically a natural death with PM burning
Most commonly a cigarette is dropped on the clothes which act as a wick - ignition source is on the body
Produces a slow smoldering fire
Body fat acts as slow burning fuel
The fire damage is localised to body and immediate surroundings but can be extensive
How long does it take to cremate a body
It takes around 2-3 hours of burning at 800-900’C
Even then cremation is not complete as still have bone fragments
What is left after a cremation
1 – 1.5 kg white calcinated bone & ash
Typically can still find ends of long bones, skull fragments, pelvic fragments
It is then crushed and put in the urn
What causes a scald
Moist heat
such as steam or hot liquid
What are the 3 main types of burn
Thermal
Electrical
Chemical
Describe the appearance of a scald
Resembles first or second degree burn
Red, swollen, blistered, painful
Well demarcated
No singeing, charring or carbonisation
Describe common scald patterns
Sparing in areas covered by clothes
Flow pattern - travels in gravity direction
Splash - often irregular
Glove and stocking - dipping hands and feet
Doughnut - caused by sitting in bath (contact areas like buttocks spared and areas out of water like knees spared)
What determines tissue damage in an electrical injury
Voltage applied
Resistance of skin (wet or dry)
Resistance of tissues (blood, nerves and muscles allow fast flow)
Current which flows (voltage and resistance)
Duration of contact (longer = deeper burn)
Direction of flow
How do you calculate voltage
Current x Resistance
How do you calculate current
Voltage / Resistance
Why is direction of energy flow important in electrical injuries
If it flows across a vital organ such as the heart, lungs or though head to brain then it can trigger fatal outcomes
Dry skin has high resistance for electricity - true or false
True - takes longer to flow so causes more burning
Therefore electricity flows better and faster across wet skin
How does electricity flow through the body
Body forms part of electrical circuit - completes it
Current flows from entry to exit along path of least resistance
Easily flows through tissues
Which flow directions can lead to fatal electrocution
Hand to opposite foot – across chest so affects heart and can trigger VF
Across chest – can cause respiratory muscle paralysis
Through head – can affect cardiac & respiratory centres in brain stem
What is the most common cause of electrocution
Most cases and deaths are accidental (often domestic electrocution)
Risk increased by wet hands and surfaces so bathroom and kitchen common sites
Much more energy flows through wet surfaces
Suicide is rare
Prolonged contact with electricity causes what
Burning
This can continue PM
Why is the 240V, 50Hz current found in the home dangerous
Likely to cause cardiac arrhythmia & arrest - V.F
Spasm of hand & forearm muscles causes victim to ”hold-on” to the source which makes the injury worse
Low domestic voltage doesn’t throw you away which prolongs contact
Describe the appearance of electrical injuries
Often no visible mark (especially if broad areas of contact or moist skin)
May have burn marks at entry and exit sites (often hands and feet)
What effect does electrical current have on muscles and nerves
They are readily paralysed as electricity passes through
How does a firm contact electrical injury appear
Collapsed blister in the center
Peripheral ring of pallor (target shaped lesion)
Surrounding zone of erythema
Metallisation of skin - green/blue discolouration if copper wire or metal impregnated into skin
What is a firm contact electrical injruy
When the body is in direct and firm contact with the source of electricity
What is a loose contact electrical injury
When the sparks leap gap between source and entry point on body
Distance depends on voltage
Can cause spread out lesions as sparks hit
Describe the appearance of a loose contact electrical injury
Melts epidermal keratin which cools to form a localised hard brown nodule
Surrounding pallor
Multiple spark lesions from HV can give crocodile skin appearance
Clothes may ignite if sparks hit them
How common are lightning strikes
Cause hundreds of deaths worldwide
Particularly in the tropics
Why are lightning strikes so dangerous
Gigantic voltages and current flow
So much energy that it just pours over the person
What are the 2 types of lightning strike
Direct strike- passes over/through victim
Indirect transmission e.g. crane driver (travels through crane to them)
or a side flash from other object such as a tree
How does a lightning strike victim appear
Clothing blown off, scorched or torn by blast
Skin burn near metal objects - jewelry, buttons or watches will become superheated and cause the burn
Arborescent markings (tree pattern -rare)
Which sites pose the risk of high voltage electrocution
Pylons and substations
May see in accidents at work
What are the effects of a high voltage electrocution
May cause spark lesions - can travel far as HV
HV may fling victim clear - may survive as contact not prolonged
Prolonged contact causes gross burning
What determines the extent of tissue damage in a chemical burn
Nature of chemical
Quantity applied
Strength / concentration
Duration of application
What are the effects of suicidal ingestion of corrosives
Rare occurrence Pain, vomiting, SOB, difficulty swallowing Perforation of oesophagus or stomach shock
What causes chemical burns
Corrosive chemical such as acids and alkalis
Usually accidental
Describe the appearance of a burn caused by nitric acid
Forms a yellow/brown scab
Describe the appearance of a burn caused by sulphuric acid
Black/brown scab
Describe the appearance of a burn caused by hydrochloric acid
White to grey scab
Describe the appearance of a burn caused by carbonic acid
Light grey to light brown scab
An acid with pH <2 has what effect on the body
It produces coagulative necrosis
An alkali with pH >11.5 has what effect on the body
It produces liquefactive necrosis
Often penetrates more deeply
List common caustic alkalis
Caustic soda (NaOH) Ammonium hydroxide (AmOH4)
Describe the appearance of an alkali burn
Grey-white mucoid burn
How is clothing typically affected in a fire
Clothing may not survive well
Some fragments may be preserved in the flexures of the body as a little more protected - neck, axilla, groin etc
How can a victims watch be useful in a fire case
Watches can be stopped by the heat of the fire
This can then be used to confirm time of death or peak of fire
Can also be used for identification - recognised by family members
How can sex be identified in a body from fire
The uterus and ovaries are rarely destroyed by fire as they are deep seated, dense and fibrous
Fire tends to fix the tissues - true or false
True
Bodies from fire don’t decompose as this heating preserves it
Which tissue is usually the more resistant in a fire
The teeth
Almost always survive a fire
What is considered an incompatible tooth difference in identification
If a tooth is present in death but absent in life (excluding dental implants but these will be obvious on X-ray )
Person cannot have got their tooth back so must be someone else
What is considered a compatible tooth difference in identification
Tooth present in life but not in death
The person may have lost it prior to death but after last living x-ray
Does not rule them out as the victim
Why is hair colour not a reliable source if identification in a body from fire
Hair colour can change with singeing
Often turns a reddish brown colour
Where does skin typically start splitting in a body from fire
Across the axillae and forearms (elbow level)
Behind the knees and across the groin
Why does the skin split in a body from fire
Skin contracts in the heat and becomes very dry
This causes it to split eventually
What causes a heat haematoma in a body from fire
Contraction of the dura and the brain
The blood in the sinuses (in dura and skull) is forced inward by the contraction which can form an extradural haematoma (accumulates between skull and dura)
What causes the laminated appearance of bone in a body from fire
It appears layered or laminated as the layers of bone will burn away sequentially
Outer layers present in some areas but burns down to inner layers in others
How can you tell if a skin split is post mortem
The underlying, exposed fat will not be soot covered if PM
Seen if the splitting occurs after the fire has gone out
What can cause the skull to fracture in a body from fire
When the inner fragile table is exposed (scalp and outer table is burnt away) it fractures easily
Heat fracture occurs in other bones too
A subdural haemorrhage in a body from fire is a fire artifact - true or false
False - in some cases it may be a genuine injury
Will be associated with ante-mortem fractures or other injury
Can tell fracture is ante-mortem if the associated scalp/fire damage is not extensive enough to have caused heat fracture
A extradural haemorrhage in a body from fire is a fire artifact - true or false
True
Usually a result of a heat haematoma
What is heat shock
A reflex cardiac arrest caused by the inhalation of hot gases
How do burns cause electrolyte imbalances
Fluid and salt is loss through the wound
Seen in 2nd degree burns and higher
What do multiple burns make you suspicious of
Deliberate burning and abuse
How can burns lead to ischaemia
Some burns will damage the underlying blood vessels
This can lead to ischaemia of the area after the burn
What causes the tourniquet effect in burns
The burn tissue swells and becomes tight
This can cut off blood supply to the area - risk of necrosis
Can also affect breathing if it occurs on the torso
What are the typical causes of car fire
Suicide
RTA
Protection against fire in place in most modern cars
What is cintering
White fragile bone that crumbles easily - post burning
Are dentures useful in identification
Yes they can be
Provided the person is wearing their own teeth!
As not permanent fixtures they are not absolute but usually a very good clue
If the person was dead at the start of the fire what does it suggest
Homicide concealment
Natural death followed by fire
Where is soot deposition most concentrated
Usually around mouth and nose as smoke is drawn in here by breathing
Soot can be swallowed - true/false
True
May be seen in oesophagus and stomach on autopsy
What part of the fire causes the burn itself
The flame
What factors must you determine with respect to a burn
Depth
Extent
Whether it was AM or PM
How does electricity cause a burn
The flow of electricity generates heat
