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Forensic Medicine > Bodies from Fire > Flashcards

Bodies from Fire Flashcards

(135 cards)

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1
Q

What are the 3 components of a fire

A

Oxygen
Heat
Fuel

All are required for a fire to propagate and burn
If any run out the fire will stop

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2
Q

List the phases of a fire

A

Incipient
Emergent smoldering
Growth of flames

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3
Q

Describe the incipient phase of a fire

A

This is when the fuel source is heated and becomes ready to burn
Start of the fire

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4
Q

Describe the emergent smoldering phase of a fire

A

There is inefficient combustion which leads to lots of smoke production
Low level burn - no flame but lots of smoke

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5
Q

Describe the flame growth phase of a fire

A

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

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6
Q

What is the cause of most fires

A

Accidents
Electrical malfunction, cigarettes, intoxication etc
Clothing may also catch fire

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7
Q

How might someone commit suicide by fire

A

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)

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8
Q

List the potential manner of death in a body from fire case

A

Natural - it can prevent them escaping (e.g. they’ve collapsed)
Accidental - cigarettes, intoxication, electrical fires etc
Suicide
Homicide

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9
Q

Fire is a common method of homicide = true or false

A

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)

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10
Q

Through which mechanisms can the fire itself cause death

A

Carbon monoxide poisoning
Smoke inhalation
Burns
Heat shock

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11
Q

What 4 questions must you answer when investigating a body from fire

A

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?

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12
Q

The cause of death in a body from fire isn’t always due to the fire itself, what other causes are there

A

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

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13
Q

How can you identify a body from fire

A

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.

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14
Q

How can a prostheses or medical device help identify a body from fire

A

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)

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15
Q

What investigation are carried out on a body from fire

A

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

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16
Q

What are fire artifacts

A

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

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17
Q

List common fire artifacts

A 
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
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18
Q

List the features of PM burning

A

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

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19
Q

What is the pugilistic posture

A

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

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20
Q

Which signs tell you that the victim was breathing during the fire (not necessarily conscious)

A

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%

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21
Q

Absence of soot below vocal folds, thermal larynx injury etc means the victim was already dead in the fire - true or false

A

False

Not necessarily - may have been a quick death so haven’t had time to inhale the smoke/CO etc

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22
Q

How can smoke inhalation cause death

A

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

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23
Q

What is carbon monoxide and why would you find in in bodies from fire

A

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

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24
Q

Describe the mechanism of death following thermal injury to the URT

A

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)

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25
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
26
Thermal injury is common in which parts of the body
Face | URT
27
What air temperature is required to cause laryngeal injury
Dry air >150'C or moist air
28
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
29
What % of Hb is considered a fatal dose of CO
50% and over | May be lower in the presence of existing heart/lung disease
30
A CO % of over 10% indicates what in a body from fire
That the victim was alive (breathing) during the fire
31
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
32
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) ```
33
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
34
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
35
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
36
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
37
How common is CO poisoning among building fire victims
85% show CO poisoning | 50% have fatal levels
38
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
39
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
40
How do particulates cause injury in fires
Superheated soot & other particulate debris passes deeper into URT than gases and cause injury
41
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 ```
42
What effect does smoke poisoning typically have on a fire victim
Gases cause incapacitation but rarely death
43
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
44
Which fuels release CO2 when burnt
All combustibles containing carbon | May also release CO
45
Which fuels release NO2 when burnt
Cellulose Polyurethanes Acrylnitrile
46
Which fuels release HCl when burnt
PVC
47
Which fuels release hydrogen cyanide when burnt
Wool Silk Nylons Polyurethanes
48
Which fuels release aldehydes when burnt
``` Wool Cotton Paper Plasters Wood Nylon Polyester resin ```
49
Which fuels release benzene when burnt
Petroleum Plastics Polystyrene
50
Which fuels release ammonia when burnt
Melamine | Nylon
51
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
52
What causes a first degree burn
Brief exposure to high intensity heat (flame) or Long exposure to low intensity heat - e.g. sunburn
53
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
54
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
55
Why are deep burns painless
The burn goes deep enough to destroy the nerve fibers so you cannot feel it anymore
56
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
57
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
58
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
59
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
60
What burn percentage has a poor prognosis
Anything over 50% | Lower in the elderly
61
Which complications of burns occur in the first 48hrs
Fluid loss Hypovolaemia - due to fluid loss Shock Renal failure
62
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 ```
63
Which complications of burns occur after 7 days or more
Infection | Tourniquet effect
64
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
65
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
66
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
67
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
68
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
69
What causes a scald
Moist heat | such as steam or hot liquid
70
What are the 3 main types of burn
Thermal Electrical Chemical
71
Describe the appearance of a scald
Resembles first or second degree burn Red, swollen, blistered, painful Well demarcated No singeing, charring or carbonisation
72
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)
73
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
74
How do you calculate voltage
Current x Resistance
75
How do you calculate current
Voltage / Resistance
76
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
77
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
78
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
79
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
80
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
81
Prolonged contact with electricity causes what
Burning | This can continue PM
82
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
83
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)
84
What effect does electrical current have on muscles and nerves
They are readily paralysed as electricity passes through
85
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
86
What is a firm contact electrical injruy
When the body is in direct and firm contact with the source of electricity
87
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
88
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
89
How common are lightning strikes
Cause hundreds of deaths worldwide | Particularly in the tropics
90
Why are lightning strikes so dangerous
Gigantic voltages and current flow | So much energy that it just pours over the person
91
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
92
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)
93
Which sites pose the risk of high voltage electrocution
Pylons and substations | May see in accidents at work
94
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
95
What determines the extent of tissue damage in a chemical burn
Nature of chemical Quantity applied Strength / concentration Duration of application
96
What are the effects of suicidal ingestion of corrosives
``` Rare occurrence Pain, vomiting, SOB, difficulty swallowing Perforation of oesophagus or stomach shock ```
97
What causes chemical burns
Corrosive chemical such as acids and alkalis | Usually accidental
98
Describe the appearance of a burn caused by nitric acid
Forms a yellow/brown scab
99
Describe the appearance of a burn caused by sulphuric acid
Black/brown scab
100
Describe the appearance of a burn caused by hydrochloric acid
White to grey scab
101
Describe the appearance of a burn caused by carbonic acid
Light grey to light brown scab
102
An acid with pH <2 has what effect on the body
It produces coagulative necrosis
103
An alkali with pH >11.5 has what effect on the body
It produces liquefactive necrosis | Often penetrates more deeply
104
List common caustic alkalis
``` Caustic soda (NaOH) Ammonium hydroxide (AmOH4) ```
105
Describe the appearance of an alkali burn
Grey-white mucoid burn
106
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
107
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
108
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
109
Fire tends to fix the tissues - true or false
True | Bodies from fire don't decompose as this heating preserves it
110
Which tissue is usually the more resistant in a fire
The teeth | Almost always survive a fire
111
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
112
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
113
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
114
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
115
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
116
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)
117
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
118
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
119
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
120
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
121
A extradural haemorrhage in a body from fire is a fire artifact - true or false
True | Usually a result of a heat haematoma
122
What is heat shock
A reflex cardiac arrest caused by the inhalation of hot gases
123
How do burns cause electrolyte imbalances
Fluid and salt is loss through the wound | Seen in 2nd degree burns and higher
124
What do multiple burns make you suspicious of
Deliberate burning and abuse
125
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
126
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
127
What are the typical causes of car fire
Suicide RTA Protection against fire in place in most modern cars
128
What is cintering
White fragile bone that crumbles easily - post burning
129
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
130
If the person was dead at the start of the fire what does it suggest
Homicide concealment | Natural death followed by fire
131
Where is soot deposition most concentrated
Usually around mouth and nose as smoke is drawn in here by breathing
132
Soot can be swallowed - true/false
True | May be seen in oesophagus and stomach on autopsy
133
What part of the fire causes the burn itself
The flame
134
What factors must you determine with respect to a burn
Depth Extent Whether it was AM or PM
135
How does electricity cause a burn
The flow of electricity generates heat

Forensic Medicine (13 decks)

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