Forensics - Fire Deaths

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Forensics

Fire Deaths

Author: Lindsey Harle, M.D. (see Reviewers page)
Revised: 9 August 2012, last major update July 2012
Copyright: (c) 2012, PathologyOutlines.com, Inc.

General
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Classification of burns:
● 1st degree: limited to superficial epithelium; erythematous with pain, edema, skin peeling; does not scar
● 2nd degree: involves full thickness epidermis and superficial dermis; skin appendages are spared; blistering, painful; usually do not scar
● 3rd degree: involves all skin layers, including full thickness dermis and skin appendages; no pain due to nerve injury; appears white; severe scarring
● 4th degree: complete destruction of skin, subcutaneous tissue and possibly bone

Documenting thermal injury:
● Extent of injury recorded as percentage of body surface area; use rule of 9s in adults, chart #2
● Age adjusted body surface area chart for children; use rule of 5s for infants and young children

Factors affecting burns:
● Heat intensity, duration of exposure, presence/absence of clothing

Types of burns
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● Flame: occurs when skin is in direct contact with flame
     • Flash burn is due to sudden explosion of gas or particulate matter; produces uniform burn over all exposed skin
● Contact: occurs when skin is in direct contact with a hot object (e.g. iron)
     • May show pattern injury reflective of the hot object
● Radiant: occurs when skin is exposed to heat waves; produces blistering and erythema
● Scalding: occurs when skin contacts hot liquid
     • Immersion burn: occurs commonly when child is placed in tub of hot water
     • May indicate child abuse; as child flexes to avoid water, areas of skin are spared around knees and inguinal region
     • Splash or spill burn: cased by splashing of hot liquid; usually accidental in nature
     • Burn pattern should correspond to the scene description, with more severe burns near the initial point of contact (e.g. child’s hand or head when a pot of liquid is pulled off the stove)
     • Steam burn: can cause severe laryngeal edema when inhaled
● Microwave: occurs when skin is exposed to electromagnetic waves; usually accidental
     • Tissue with higher water content shows more severe injury (e.g. muscle burns more rapidly than fat)
● Chemical: occurs when strong acids or alkali contact skin; can also be caused by phosphorus or phenol
     • Burns develop more slowly than those created by thermal injury
     • Alkali agents tend to cause more severe injury; are usually full thickness and appear pale and leathery
     • Acid burns usually are partial thickness and appear erythematous and erosive

Mechanism of death
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● Immediate mechanism of death due to thermal injury
     • Neurogenic shock secondary to severe pain
     • Hypovolemic shock and acute renal failure due to loss of fluid from skin
     • Toxic gas inhalation – CO (most common), cyanide, acrolein, nitrogen dioxide, hydrochloric acid
          • Often see soot in nose/mouth
          • May produce edema, mucosal necrosis of upper airway, or bronchospasm
          • CO levels usually 30-60% in fire deaths
● Delayed mechanism of death due to thermal injury
     • Delayed hypovolemic shock with renal failure
     • ARDS
     • Infection (pneumonia, sepsis, cutaneous)
     • Pulmonary embolus due to immobilization

Postmortem changes in charred/burned bodies
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     • Pugilistic attitude: flexion of the upper extremities as the body cools
     • Does not reflect ante- or perimortem body position
     • Skin/muscle splits: occur parallel to muscle fibers; can extend into body cavities
     • Should not be confused with antemortem trauma
     • Loss of fingers/toes/extremities: due to charring or loss at the scene
     • Heat epidural: blood boiling out venous sinuses produces postmortem epidural blood pooling
     • Weight and length measurements are unreliable

Classification of fire deaths
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● Death due to an intentionally set fire is generally a homicide
● Suicidal if the individual sets him/herself on fire
● Look for accelerants or volatiles on clothing from the decedent
● Many fires are accidental
● Antemortem versus postmortem burn
• Postmortem burns may appear yellow and dry; microscopic evaluation should reveal no inflammatory reaction
• Some postmortem burns can be impossible to distinguish from antemortem burns

End of Forensics > Fire Deaths

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