Forensic Pathology of Thermal Injuries

Updated: Oct 18, 2016
  • Author: Valerie J Rao, MD; Chief Editor: J Scott Denton, MD  more...
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Overview

Overview

Burns of skin or other tissue are caused by fire, radiant heat, radiation, chemical, or electrical contact. Thermal burns result from any external heat source (flame, hot liquids, heated solid objects, or hot gases). Fire-related deaths may also result from inhalation of carbon monoxide and other toxic products of combustion, including cyanide.

Additionally, there are many nonthermal types of burns, which will be discussed briefly. Radiation burns result from prolonged exposure to solar ultraviolet radiation or other sources and are very rare in the forensic arena, as these individuals survive unless there are other factors contributing to the fatal outcome.

Chemical burns result from exposure to strong acids, strong alkalis, phenols, cresols, mustard gas or phosphorus, with deaths from acid and alkali burns being most common. These agents can be ingested or come into contact with the external surface of the body and with resultant geographic burns.

Electrical burns result in injury to the skin at points of contact to the electrical source; on occasion, the cutaneous burn is very inconspicuous and can be missed entirely. The mechanism of death is cardiac, resulting in ventricular fibrillation with, at times, little or no tissue destruction at the contact point.

Similar to electrocution, death from lightning results in cardiac arrhythmia and asystole, with a paucity of cutaneous findings. Occasionally, a Lichtenberg figure, also known as ferning or keraunopathy, may be seen. This is observed as an arborizing or ferning pattern on the skin. This phenomenon is transient and poorly understood but may be related to intravascular hemolysis.

The following is an example of a postmortem artifact on a body following burning.

Pugilistic attitude as a result of heat-related co Pugilistic attitude as a result of heat-related contractures.

See also the following:

Historical information

Fire deaths are some of the most challenging fatalities, both from the investigative and the autopsy aspect. One reason is the multifactorial investigative team approach to a fire death and the inevitable contamination of the scene. The first wave of investigators is the fire department personnel armed with powerful hoses, followed by the police, and then the medical examiner and his/her investigator staff. In between, one has to deal with the news media and the curious immediate public.

Oftentimes, the fire is still smoldering as the flames are being extinguished. The debris can be massive, and all semblance to a dwelling place is destroyed. Investigators may pass the charred body(ies) a few times before the decedent(s) is(are) located at the scene. Once safety to enter the dwelling is established, only then can the arduous task of putting the pieces of the puzzle together begin.

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Fire-Related Deaths

Fires and burns are the fifth most common cause of mortality from unintentional injury in the United States, and they comprise the third leading cause of death due to injury in the home. The US ranks seventh in the world for mortality rate from fires (among the 25 developed countries for which statistics are available). [1]

According to the US Fire Administration in the Department of Homeland Security, 3220 civilian individuals in the US lost their lives as the result of fires in 2008. [2] The vast majority of those deaths, 84%, occurred in residences. Slightly less than 10% (315) were the result of purposefully set fires. [2]

The majority of fatalities arising from thermal burns occur in buildings, but fire-related deaths can occur in any location, commonly including motor vehicles or aircraft. Key questions that must be answered include the identity of the victim(s) and the circumstances surrounding the fire. Additionally, the investigation must address issues such as: Was the victim alive during the fire? Was the fire set after the death of the victim in an attempt to conceal a crime? Were there factors that rendered the deceased unable to escape the conflagration?

In most fire deaths, the cause of death is the inhalation of carbon monoxide and other products of combustion. The incineration of the body follows. It is difficult to tell at what point in time the person expired during a fire; however, it is fairly easy to establish whether the person was alive while the fire was ongoing.

A forensic autopsy with extensive photography is essential to answer the many questions that will follow a death due to a fire. The cause and manner of death will be determined after the scene examination, and consideration of the medical and social background of the decedent, the autopsy findings, the police investigative report, and the fire marshal's findings. In an effort to establish the identity of the dead, total-body radiographs, dental radiographs, and ultimately, DNA evidence may be necessary, dependent on the degree of destruction of the body. Total-body radiographs should also be performed to identify any foreign bodies or projectiles, aiding in ruling out other causes of injury or death before the fire.

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Thermal Injury Terminology

This section will briefly review the following terminology commonly discussed in relation with thermal injuries in forensic pathology:

  • Cherry red lividity
  • Epidural hematoma
  • Fire fractures
  • Lichtenberg figure, ferning, keraunopathy
  • Pugilistic attitude
  • Skin splits
  • Soot

Cherry red lividity

In individuals with a significant carboxyhemoglobin concentration in the blood (due to carbon monoxide exposure), the livor mortis has a distinctive, bright, cherry red color. Carbon monoxide is an odorless, colorless gas with the same density as air. The affinity to bind to hemoglobin is 200-250% that of oxygen. Carbon monoxide is produced from an incomplete combustion of hydrocarbons during a fire. Other products of combustion (most importantly cyanide) may also be found in the blood on toxicologic analysis.

Cyanide may also produce a bright red coloration of the blood and muscles of the body and has a characteristic bitter almond smell that is only detectable by a select segment of the population having the genetically determined capability. Its smell is typically detectable in cyanide poisoning resulting from massive ingestion, whereas its smell may not be apparent in fire-related deaths.

Epidural hematoma

In burned bodies, epidural hematoma results from blood and marrow in the cancellous diploe of the skull boiling and being extruded by the intense heat, resulting in a brown, granular, and at times foamy or dried and flaky deposit in the epidural space. This is also a postmortem heat-related artifact and is easily distinguished from an antemortem epidural hematoma by the difference in color and texture. Furthermore, antemortem hematomas are often associated with linear skull fractures, with injury to the middle meningeal artery.

Fire fractures

Fire fractures are another postmortem heat-related artifact and should not be confused with antemortem injuries. Because of the extreme heat, the muscle, tendons, and soft tissue are charred, resulting in exposure of the underlying bones to heat, with resultant heat-induced fractures.

Skull fractures are usually seen on the temporal bones, often radiating from a central point. The fractured edges are ragged and may cross suture lines, unlike antemortem fractures that usually terminate at suture lines. Additionally, these fractures may be of partial thickness, with exposure of the cancellous layer.

Lichtenberg figure, ferning, keraunopathy

Keraunopathy is most generally the study of lightning-related injury, and the term is also used occasionally as synonymous with ferning, the arborizing pattern of skin discoloration seen on some bodies after a lightning strike. The finding can be seen on both living individuals surviving a lightning strike and those dying of it.

The Lichtenberg figure is another term for this same finding, but it can also be applied to objects other than the body. Lichtenberg figures were originally described on insulating surfaces subjected to a high-voltage discharge. Lichtenberg figures, or ferning, on the human body can be transient, lasting hours to days, and their cause remains unclear, with theories including the hemolysis of erythrocytes or rupture of capillaries along the arborizing pattern of electrical discharge. However, studies undertaking histologic examination of the figures showed no demonstrable histopathology. [3]

Not every lightning-caused death will demonstrate ferning, and in fact, it was present in only approximately one third of 45 individuals in a study by Wetli of victims of fatal lightning strikes. [4] Other cutaneous injuries may be seen, such as burns over sizable body surface areas or smaller punctate burns; the tympanic membranes were ruptured in over 80% of cases in Wetli's study. [4]

Pugilistic attitude

The burned body assumes what appears to be a boxer's stance (see the first image below). This is a postmortem artifact resulting from the effects of heat on the muscle protein: denaturation and dehydration. The flexors are bulkier than the extensors, and hence, the overall effect is one of contractures, with flexion at the elbows, wrists and knees. Often the joint spaces are exposed and the articulating surfaces of the bones are charred (see the second image below).

Pugilistic attitude as a result of heat-related co Pugilistic attitude as a result of heat-related contractures.
In fire-related deaths, heat-induced contractures In fire-related deaths, heat-induced contractures result in exposure of the peripheral joint spaces, with charring of the articulating surface of the bones.

Skin splits

Skin splits are usually seen on or near joint surfaces, the extensor surfaces of the extremities, and the head. These splits can extend to the underlying adipose and skeletal muscle, dependent on the intensity of the heat. These are also a postmortem artifact. The muscles split parallel to the long axes of the myofibers rather than across them. The soft-tissue splits may be full thickness, particularly on the abdomen, resulting in charring of the exposed bowel surface (see the following image).

Skin and subcutaneous splits due to intense heat. Skin and subcutaneous splits due to intense heat.

Soot

Soot is an amorphous black material found in the airways (mouth, nares, trachea, bronchi) of individuals inhaling smoke during a fire (see the image below). Its presence in the airways at autopsy indicates that the decedent was breathing and thus alive during the fire.

Soot deposition on tracheal mucosa and the dorsum Soot deposition on tracheal mucosa and the dorsum of the tongue.
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Forensic Scene Findings

The focus of the scene investigation is multipronged in fire-related deaths; the questions to be answered include the following:

  • What is the identity of the decedent?
  • Was the individual alive or dead before the start of the fire?
  • What was the cause of the fire?
  • Was the person impaired in some way and hence rendered incapable of exiting the burning building or the burning vehicle?
  • Are the injuries antemortem or postmortem?

Answering these questions will also allow for determination of the manner of death. To answer these questions, several agencies must work as a team. The fire marshal, law enforcement officials, and the medical examiner, in that order, will attempt to reconstruct the incident. Although the autopsy may yield the final answer to some of these questions, consideration must begin at the scene.

The medical examiner is called to the scene after law enforcement officials and the fire marshal have processed the scene but before the body is moved. At times, this in situ scene examination of the body becomes important in understanding the final moments of the deceased. Importantly, the location and position of the body should be recorded photographically.

Questions that should be posed to the investigating agency include the following:

  • Does the victim drink, smoke, or use illegal drugs?
  • Does he/she have any medical condition that could hamper or impede escape from the fire?
  • Was the body found close to a doorway or other escape route, suggesting that he/she tried to exit the burning structure?
  • Is there any indication that the fire was intentionally started, perhaps even to cover a crime? Intentionally set fires may be the result of suicide, homicide by fire, or even an attempt to disfigure or destroy a body that resulted from another method of homicide, such as gunshot wound before the fire.

When the cause of death is suspected to be low-voltage electrocution, from a faulty appliance, or a faulty electrical outlet, the scene examination is often paramount in establishing the cause of death. The contact point on the body may be so very minute that it could be overlooked. The presence of an appliance plugged into an outlet adjacent to the body which is otherwise free of trauma should arouse suspicion as a possible cause of injury resulting in death. The appliance should be impounded and examined by a competent investigator (ie, an electrical engineer or an individual who has knowledge of the appliance). A radiograph of the appliance (dependent on its size) can also reveal a flaw within its "housing" that could account for the death.

Determination that lightning is the cause of the death is often based on a thorough scene investigation, as the postmortem findings can be minimal to none. Records pertaining to the weather at the time of the incident and, if available, eyewitness accounts, will greatly aid the death investigation process.

Deaths resulting from caustic chemicals are evident from the scene evaluation, the social and medical history of the decedent, and the autopsy findings (ie, the presence of chemical burns. However, burns from caustic chemicals may also occur postmortem, including those occurring due to the application of bleach to a body after death in order to attempt to destroy evidence or render the body unrecognizable. [5]

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Trace Evidence

The jurisdiction for evidence collection at the scene most often lies with the fire marshal and law enforcement officials. Evidence collection from the body, however, is the domain of the medical examiner in most jurisdictions. Collection of fabric or clothing from the body should be accomplished as early as possible in order to preserve volatile accelerants. The items should be placed in airtight containers, such as clean, unused paint cans. Other evidence that may be with the body includes identification cards, receipts, or drug paraphernalia (depending on the severity of the fire's effects).

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Gross Examination Overview

Classically, the severity of thermal burns is classified according to the depth of tissue damage. First-degree burns are limited to the outer layer of skin. A good example is a sunburn. There are no blisters, but the damaged layer may peel. Second-degree burns cause damage to several layers of skin, resulting in blisters that, when healed, may result in scars. Third-degree burns destroy the entire thickness of the skin, both the epidermis and dermis. Scarring is the rule. Fourth-degree burns result in charring of skin, of deeper tissue, and sometimes, of bone.

However, these are clinical guidelines and are only useful when there has been postinjury survival of at least a few hours, such that there has been time for vital tissue reaction, including edema, erythema, inflammation, and hemorrhage. Without a vital reaction, the degree of injury can only be classified as to partial- or full-thickness burns relative to the skin. Thus, partial-thickness burns in a fire victim dead at the fire scene or expiring very shortly thereafter will appear at autopsy only as reddened skin with varying degrees of superficial skin slippage that results from the loosening of outer layers of the epidermis. Full-thickness burns manifest as brown or brown-yellow dried, leathery skin; obviously charred, blackened skin; or completely burned away skin, exposing thermally coagulated or charred muscle, bone, or internal organs.

The extent of burns over the surface of the body can be expressed as a percentage of the total body surface area, and it is estimated clinically using the "rule of nines" (see the image below). This table is useful in the living when planning therapy and estimating survivability. This rule of nines applies to any sort of burn, but it is most frequently employed with thermal or scalding burns that may cover a relatively large surface area.

Rule of nines for calculating burn area. Rule of nines for calculating burn area.
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Internal Examination

Despite extensive thermal injury to the outside of the body, the viscera is often well preserved. Cherry red lividity to the soft tissue and blood in the organs, is usually evident with carboxyhemoglobin levels above 30%. Antemortem injuries should be sought in the organs, and all natural disease documented.

A major role of the autopsy is to exclude the possibility that the fire was merely concealment of a homicide occurring by other means, including gunshot wound, sharp force injury, or blunt force injury. Antemortem injury can be identified despite the fire damage to the body. Bruising can be identified on dissection of the soft tissue, manifesting as hemorrhage in the subcutaneous tissue. Lacerations can be distinguished from fire-related skin and muscle splits in that lacerations often result in injury across (perpendicular to) muscle fibers rather than fire-related skin and muscle splits that are in the longitudinal plane of the muscle. [6]

Antemortem gunshot wounds that result in lethal visceral injury can be documented, by the hemorrhagic tracks through soft tissue and organs, hemorrhage within body cavities (such as the hemothorax, hemoperitoneum), and bony fractures, or perforations. Radiographs will demonstrate radiopaque missiles, if present (see the following images). Bombings may result in fire, and radiopaque bomb components or shrapnel within the body may be evident on radiographs.

Total body radiographs occasionally reveal radiode Total body radiographs occasionally reveal radiodense objects that need to be investigated. In this case, the decedent was wearing an ankle holster with a gun and ammunition. Because of the heat, one of the bullets was discharged and located in the shoe. Radiographs are also used for identification purposes.
This image depicts a recovered missile from the sh This image depicts a recovered missile from the shoe of the decedent in the previous image.

Lastly, the presence of soot in the airways (nasopharynx, trachea, and bronchi) is incontrovertible evidence that the decedent was alive and breathing at the time of the fire (see the image below). The presence of soot is typically correlated with elevated blood carboxyhemoglobin levels.

Soot deposition on tracheal mucosa and the dorsum Soot deposition on tracheal mucosa and the dorsum of the tongue.
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Scalding

Scalding injuries are burns due to the application of heat by direct contact with a hot liquid via splashing, pouring, or immersion in the fluid, or by exposure to hot vapor (a visible suspension in the air of particles of some substance, the gaseous state of a substance that is normally a solid or liquid). The pattern and severity of the burns received are different from those received by exposure to a broader source of heat or flame or from contact with a very localized, hot solid object.

Hot liquids burn only where contact is made with the body. Whereas exposure to a fire burns the skin surface facing the fire, hot fluids flow with gravity away from the initial contact point and thus can burn all along the course of the flow, until the fluid leaves the body or cools sufficiently. The degree of severity of the burn may decrease as the distance from the point of contact increases, as the liquid cools along its course.

In addition, clothing tends not to burn with scalding situations, as the fluid temperatures are almost always below the burning point of clothing but well above the thermal tolerance of skin. Thus, the fluid can also soak into and pass through and under clothing and can easily burn beneath clothing, including into skin folds, which are typically very protected from radiant-heat burns. Furthermore, with very hot liquids, the clothing can trap the fluid and even prolong or intensify the burns.

With vapor or steam, unclothed, exposed areas are most prone to injury. Mucous membranes, especially the eyes, are very susceptible to these kinds of burns. It has been said that a common eye injury in recent years occurs when just-cooked microwave popcorn bags are opened close to the face, and trapped hot water vapor (steam) is suddenly released and hits the eyes.

At-risk populations

Scald injuries can happen to any age group, but infants, young children, older adults, and the disabled are most at risk. Children have curiosity, limited understanding of danger, and limited ability to react quickly to hot liquid. The elderly and those with disabilities may have impaired mobility, sensory impairment, or decreased mentation. In addition, thinner skin with children and the elderly means that burns can extend more rapidly to greater depths. These high-risk groups are more likely to require hospitalization and suffer complications, and their recovery is more difficult. Tens of thousands of children are treated in hospital emergency departments for scald injuries in the United States each year, with scalds being the number one cause of burn injury to children younger than 4 years. [7]

Liquid scalds

Hot water, including tap water in bathtubs and showers, is the leading cause of both scalds and hospital admissions for burns. [8] Each year, approximately thousands of injuries and numerous deaths occur in the home due to scalding from excessively hot tap water. The majority of these injuries involve the elderly and children younger than 5 years. [8]

In general, scalding severity is related to the temperature and volume of the liquid and the duration of contact with the liquid. [9, 10] Cooking oil burns as compared to water burns are potentially more severe because of the much higher boiling point of oil. However, scalding occurs most commonly with hot water from bathroom taps, usually by accidental operation by children while bathing or washing, particularly if they are left unattended, and the hot water supply is set at above 120°F.

At higher water temperatures, much less exposure time is required to produce a full-thickness scald. Water at 65°C (149°F) produces a full-thickness burn in less than 1 second of exposure; at 60°C (140°F), in about 5 seconds; and at 55°C (131°F), in about 30 seconds. With water at 50°C (122°F), 5 minutes' exposure would be required to produce full-thickness burns. In addition, the volume of the fluid exposure with hot water is usually much greater than with cooking or drinking fluid exposures, again due to the bathtub-related nature of the exposure. The duration of contact is also affected by the texture or composition of the fluid—if it is sticky or thick, then the burns are usually more severe.

Scald burns are usually of partial thickness but can be full thickness with greater temperature or longer contact; charring does not occur. Erythema, edema, and blistering are the usual results, but there will be skin necrosis with full-thickness burns. Death is typically delayed, and often related to secondary complications, such as infection and shock, from loss of the integument.

In the kitchen or dining area, scalds often result from spills while an individual is handling or moving hot foods, liquids, or drinks, or, when children are involved, from reaching up and overturning cooking pots or cups or other containers of hot food or fluid. In the bathroom, inadvertent scald injuries result from people accidentally turning on hot water and being unable to remove themselves from the water.

Internal injuries from scalds are rare, unless the hot liquid is ingested or forced inside a body cavity. The severity of the internal burns then would be related to the temperature resistance of the mucosal surface in contact, with the oral cavity being far more tolerant than the esophagus or other areas of the gastrointestinal tract. Possible complications of such internal burns include significant infection and pneumonia, stricture formation, and malnutrition if the alimentary tract is so damaged as to hinder eating and drinking.

Intentional scalding

Intentionally inflicted scalding can be a component of child or elder abuse, and the pattern of the injuries can be very important in determining that the burns are inflicted rather than inadvertent. Intentional immersion of a limb or portion of the body into hot liquid results in a typical "stocking" or "glove" pattern of burn injury with a clear line of demarcation, as shown in the image below. Additionally, both feet may be involved if a child is immersed by another individual in a too-hot bath, and other areas of the body will show water-level lines of demarcation, often with a symmetrical appearance involving left and right limbs equally. There may be sparing of areas of folded skin, such as the inguinal folds and popliteal fossae, and sparing of areas pressed against the relatively cool porcelain tub, such as the buttocks.

This image illustrates scalding injury resulting i This image illustrates scalding injury resulting in a full-thickness immersion burn. Note the demarcation of the burned area to the uninvolved skin.

If the scalding fluid is caustic in and of itself, such as a gasoline, there can be chemical burns in addition to the thermal burns, but usually under these conditions the liquid has not been ignited. If the flammable liquid has been ignited, the burns will take a more typical thermal appearance.

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Chemical Burns

Chemical "burns" are far less frequently encountered than thermal burns, most often presenting to the forensic pathologist as a death days to months removed from the original injury. [11] Ingestion of caustic chemicals is the most common underlying cause of death. These injuries are not actually due to heat of the chemical reaction but, rather, are from the direct interaction of the chemicals with the molecular structures of the tissues. The chemicals break down mucosal linings with loss of their function, result in the accumulation of necrotic tissues and fibrinopurulent material, and facilitate ingress and spread of bacterial infection. More often than not, the manner of death is suicide when the deceased is an adult. Children playing with corrosive liquids can also accidentally suffer this type of injury.

When a strongly acidic chemical is consumed, death results from the acute destruction of internal organs and the liquid "burns" from inside out. The mouth, tongue, esophagus, stomach, and adjacent viscera are hardened, gray, and very firm on the outer aspect, with more normal tissue noted in the deeper portions of the organs. This pattern of injury is common following ingestion of sulfuric acid in particular. The mouth may also have a splash or drip pattern of surrounding perioral burns if the liquid is consumed. See the following images.

Acid burns, resulting from ingestion of sulfuric a Acid burns, resulting from ingestion of sulfuric acid. Note the burns to the mouth and the spill pattern on the face and chest, in contrast to a thermal pattern of injury.
Note the spill pattern on the anterior chest and a Note the spill pattern on the anterior chest and abdomen of the decedent from the previous image.
Burns from the acid, on the tongue, hypopharynx, a Burns from the acid, on the tongue, hypopharynx, and airway of the decedent from the previous image.
Acid injury extending through the viscera and onto Acid injury extending through the viscera and onto the pleural surface exposing the ribs of the decedent from the previous image.
Coagulation necrosis of the solid organs from the Coagulation necrosis of the solid organs from the acid of the decedent from the previous image.

Alkali burns are similar in destruction of tissue, depending on the concentration of the liquid. Significant prolonged morbidity often complicates such chemical ingestions, resulting in numerous hospitalizations and severe physical and social debility. Potential complications include mediastinal infections and fistulas; pneumonia; poor nutrition from esophageal dysfunction or strictures; and respiratory insufficiency or airway obstruction from either direct upper airway destruction by the chemical or the typical aftermath of a chronic tracheostomy required during the long treatment period with such injuries.

When a complication of chemical burns leads to, precipitates, or contributes to a death, even if months or years after the initial insult, the manner of death will correctly be assigned to the initial event resulting in the injury. It may be suicide, if the ingestion or exposure was intentional and self-inflicted, or accident or homicide, as the investigation and history dictates.

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Special Autopsy Procedures

In this section, photographic documentation, toxicologic analyses, DNA analysis, radiography, and microbiologic cultures are briefly reviewed.

Photographic documentation

Special photographs in fire deaths include the following: the nares, dorsum of the tongue, the open larynx, trachea, and major and smaller airways to document the extent of soot deposition in the airways. The presence of soot in the airways is incontrovertible evidence that the decedent was alive (and breathing) at the time of the fire and did, in fact, survive for a while exposed to the fire. This usually correlates with an elevated carbon monoxide level in the blood.

Toxicologic analyses

Peripheral blood and urine samples should be obtained to determine the presence or absence of drugs and alcohol. Skeletal muscle is considered a second-line specimen if blood is unavailable for determination of the carboxyhemoglobin level. Ocular fluid and bile may also prove useful for analysis in these cases.

DNA analysis

A blood specimen should be collected for DNA analysis in the event that less time-intensive means of identification fail. A section of long bone including marrow, such as femur, can be analyzed if blood is not available. Teeth with pulp can also be assayed.

Radiography

Total body radiographs should be done on all charred bodies. [12] This can lead to scientific identification when compared to antemortem radiographs if the victim had been to a hospital for some previous illness requiring radiographs or had an implanted prosthetic device. Radiographs should also be taken to rule out the presence of bullets or components of incendiary devices.

Microbiologic cultures

Microbiologic cultures (bacterial, viral, and fungal) should be considered in persons who have survived for some time after the burn incident. The leading cause of death in patients hospitalized after burn injury is sepsis, followed by pneumonia. [13] Fungal infection is also common, with the propensity increasing the longer the wound has been present; nearly half of autopsied individuals in one study showed the presence of fungal elements. [14]

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Histology and Microscopic Examination

The ideal histologic sections for microscopy document significant natural disease processes, such as coronary arteries with significant narrowing by atherosclerotic plaque, or myocardium documenting hypertrophy or scarring.

Sections of lung may show the presence and extent of anthracosis and emphysematous change that could document cigarette smoking, which may help to explain the source of a fire. Additionally, a section of the larynx and bronchus can be taken to document the presence of soot as well as antemortem thermal injury to the mucosa of the airways, characterized by a vital reaction of the mucosal lining.

Histologic examination of the liver may assist in identifying steatohepatitis or cirrhosis in an alcoholic. Chronic alcoholism may contribute to the start of a house fire if an individual is intoxicated and less aware of their surroundings. It may also explain why an individual was unable to escape a fire.

Histologic examination of the edge of a burn, to include both the burned area and adjacent grossly unburned skin, may reveal vital reaction microscopically, consisting of acute inflammation, hemorrhage, edema, and necrosis. These findings are present only in antemortem burns, thereby assisting in the delineation of whether the decedent was alive when the burns occurred. Additionally, a section of the skin in electrical burns may document necrosis, vertical streaming of the epidermal nuclei, and homogenation of the dermal collagen. Microscopic findings must be corroborated with the gross examination of the documented injury.

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Ancillary and Adjunctive Studies

Numerous ancillary studies have been mentioned elsewhere in this article (see Special Autopsy Procedures), but they will be listed here for completeness. In fire-related deaths, ancillary studies that must be performed include total body radiographs (in bodies with any charring or nonintact skin); quantification of carboxyhemoglobin in the blood; and toxicologic testing for drugs and alcohols.

A blood cyanide level may be helpful in cases with an inexplicably low blood carboxyhemoglobin despite the presence of soot in the airways. In addition, testing of clothing or evidence from the scene can be performed by the partnering crime laboratory to determine whether accelerants were involved in a fire.

As a general rule, a blood carboxyhemoglobin concentration greater than 50% is expected in deaths due to the inhalation of products of combustion. Deaths may occur at lower levels than this, however, [15] particularly in elderly persons and in persons with cardiac disease. Normal carbon monoxide levels can occur in victims of flash fires, as in a conflagration in which the intensity of the fire is so extreme that death is almost instantaneous.

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Identification of Bodies in Fires

Severe fires destroy commonly used identification items, such as personal effects, fingerprints, and even teeth. Care should be taken with fire victims to look for remnant personal effects, including identification cards and jewelry, and for unburned skin with tattoos or printable fingertips. Care should be taken not to break or lose burned teeth before dental charting and radiographs can be done to document the dentition for comparison to antemortem dental records. Superglue mists or sprays have been used to help "cement" in place charred or fragmenting burned teeth to help with this.

The postmortem height of a burned body is not a reliable indicator of identity because of the shrinkage of tissues and contractures of extremities caused by a hot fire. Eye color is also another unreliable factor because of heat-induced cloudiness of the corneae and coagulation of the globes. However, tattoos and scars can be very good circumstantial identifiers and, oftentimes, can be visualized despite the burned skin. A surgically absent appendix, gallbladder, or previous surgery can also corroborate identity. Surgical implants and prostheses are indisputable ways to identify the decedent, if present and unique.

Positive scientific identification is necessary in most fire-related deaths. Comparison of antemortem and postmortem dental radiographs by a forensic odontologist is an excellent means of accomplishing this. Dentition with restorations will lead to the easiest identification, in a charred body having no remaining fingerprints. Denture plates, both complete and partial, may present another form of identification. In the event that the skin of the hands remains intact, a search for antemortem fingerprint exemplars (from governmental agencies, law enforcement encounters, or employment records) may provide a means of identification. If the skin of the palms comes off as a glove ("degloving"), this can be used to obtain prints for comparison at a later date if antemortem fingerprint exemplars are located.

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Patterns of Thermal Injuries

In this section, patterns of burn injuries will be discussed, which may aid in the determination of how burns occurred and whether they were inflicted (intentional) or inadvertent (accidental).

Scalding

With scalding, the pattern of the injury is especially useful for assistance with the determination of manner of injury or manner of death (accident vs homicide). Scalding frequently occurs in child abuse situations, in which a body part, or even the entire body, is dipped or immersed in a hot fluid or has a hot fluid poured over it. In cases of child abuse, the perpetrator does not wish to be burned and often does not totally immerse the child in hot bath water where splashing could occur; thus there will be specifically shielded parts of the child's body where the child had been gripped by the perpetrator that will not have the scalds, often the wrists, upper thorax, upper arms, or ankles (see the following image). Usually the child retracts from the water/heat or fights the situation and may even be balled up, resulting in sparing of the body creases from burns.

This image illustrates scalding injury resulting i This image illustrates scalding injury resulting in a full-thickness immersion burn. Note the demarcation of the burned area to the uninvolved skin.

Postmortem positioning of the child's body by the death investigator to reach a theoretical horizontal fluid level exposure that matches the injuries on the body, either by direct manipulation of the body or by mental or photographic manipulation of the body, can be performed to show how the body may have been immersed. Two-dimensional thinking of a rigid, upright body will not assist in determining such a pattern, but rigor must be broken and the body positioned to show this horizontal fluid level for pictures and diagrams. Such "reenactments" provide a very graphic representation of the nonaccidental nature of such an immersion.

If a fluid has been poured on a child, additional splashing on the body will make the scalding pattern irregular due to the run-down of the hot fluid and secondary scalds due to splashing. The central contact point with rundown rivulets or tributaries emanating from the one point, however, can usually be demonstrated, depending upon the presence of clothing, the volume of liquid, and secondary movement of the "target" victim. For example, if hot fluid is poured onto the top of the head and the child reacts, if the head is flexed toward the chest, then the fluid would run off the forehead and sides of the head and down the neck and drip off the sides of the face, sparing the very central face. As the fluid dissipates its heat and decreases its individual rivulet volume down the body, the shoulders, back, chest, arm, and even more dependent areas would receive less of the fluid and less burns.

As with immersion, consideration should be made as to the body position at the time of the exposure to the fluid in relation to the detected injury areas, with an attempted recreation of the incident. If a possible accidental overturn of a hot cooking fluid or hot drink container is at issue, the pattern may be directly on the face or head from the child reaching up and pulling a pan or pot over on himself. Again, the pattern will depend upon the volume, temperature, and nature of the fluid. With this situation, the height and arm reach of the child are important, and measurements of body height and arm length are important to try to answer whether a child could indeed reach a pot without standing on another object. If the scalds are of the forearms, abdomen, groin, and anterior lower extremities, a spill of a carried container or from a table top to a seated victim may be more likely.

Patterned contact burns

Patterned contact burns, from direct contact with a hot object, are often a sign of abuse. Items such as a clothing iron, hair curling iron, waffle maker, or heated metal implement such as a heated fork have been used to inflict injuries and these implements leave a burn of a distinctive shape. Burns from the application of the lit end of a cigarette to the skin result in a round burn which heals to a scar of a similar shape; the size of the burn is also a feature that aids in identification of its source.

Burn and soot distribution

The pattern of the burns may be useful in determining the origin of the fire in relation to the body position at the time they were received. Depending on the distribution of burns on the body, there may be indicators as to whether the victim was asleep and unmoving when the fire began or if he was trying to flee the source of the fire.

The pattern of soot on the body can likewise tell a lot about the position of the body after unconsciousness or death has occurred but the fire has continued—soot will be greatest on the nondependent surfaces, in general.

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Common Misconceptions

Numerous postmortem heat-related artifacts have been discussed in earlier sections, particularly in the Thermal Injury Terminology section.

Cutaneous conditions

Other cutaneous conditions, particularly bullous conditions or those with epidermolysis, may mimic burns. Stevens-Johnson syndrome is one such example, with erythematous, coalescent areas of skin ulceration. It is important to recognize bullous dermatitides to avoid erroneous allegations of abuse.

Spontaneous human combustion

A historically commonly held but certainly wrong theory is that of so-called "spontaneous human combustion." The concept had been invoked to explain fire deaths in which the core of the body (torso, head) appeared to have burned suddenly, while the fire left the extremities intact and often did little damage to the surrounding residence. Many of these incidents occurred with obese individuals. However, in the majority of cases, some cause for the fire could be identified, especially cigarette smoking. This phenomenon is at most a particular subtype of fire-related death associated with wicking, rather than a supernatural event. The wick effect is seen when a smoldering fire is perpetuated by melting fat from the body, similar to how a candle fuels the small fire on its wick. [16, 17]

Cremation

Another misconception often held by criminals is that fire will completely destroy, or "cremate" a body in order to hide a crime. Despite severe burns and even charring, other injuries—whether blunt, sharp, or related firearms—can usually be demonstrated in burned bodies by cut-down of the soft tissues, radiography, and internal examination. In this sense, attempts by criminals to disguise prefire homicidal injuries by setting the environs of the body on fire or by burning the body itself usually fail miserably. Even many ligatures survive fires, especially those with internal metal components (eg, plastic electrical cords).

Hours of exposure to temperatures over 2000°F are typically required to cremate a human body, and most set fires on a body and most house fires do not achieve those conditions, even with accelerant use, especially if firefighting activities begin soon after the fire is started or discovered. It should be readily apparent that a complete autopsy is recommended in burned bodies to document antemortem injuries and obtain samples for toxicologic analysis.

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Issues Arising in Court

Legal issues regarding thermal injuries pertain to insurance claims, inheritance issues, and possible criminal investigation. Questions as to cause of the fire, identity of the deceased, cause of death, and manner of death must be addressed. A key question will be whether the fire occurred antemortem or postmortem, which can be determined on the basis of any other antemortem lethal injuries (such as a gunshot wound), the blood carboxyhemoglobin level, and the presence or absence of soot in the airways.

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