Forensic pathology of thermal injuries involves establishing the type of burn, identifying the cause of death, and identifying the victim. Fire results in damage to skin and deep tissues, while charring and the turning of the body to ash can result from prolonged exposure to high temperatures. Electrical burns can be either high or low voltage, and these burns characteristically present at entry and exit points in the body. Electrocution can harm internal tissues and organs more severely than the epidermis. Chemical burns vary in character depending on whether the chemical is acidic or alkali. Radiant burns of high severity cause the skin to turn leathery and brown. Identification is made of burn victims primarily through tissues that are usually preserved in the case of fire.
Forensic Pathology of Thermal Injuries
A thermal injury, known also as a burn, is a type of injury that occurs due to exposure to heat or, alternatively, to chemicals, that results in damage or destruction to body tissues (Rao, 2014). Thermal injuries can occur in a variety of different forms depending on the physical effect the burns have on body tissues and also based on the different kinds of substances that cause the thermal injury. Thermal injuries result in deaths about two percent of the time in children, and about twenty eight percent of adults who experience thermal injuries die either from burns or burn-related complications (Spitz, Clark, Fisher, & Spitz, 2006). The extent of bodily damage from thermal injuries depends on time of exposure to heat and on the type of burn. The extent of the damage caused by thermal injuries is classified based on the intensity of tissue and bodily injuries sustained from the exposure to heat. First-degree burns, the least serious classification of thermal injury, exhibit tell tale signs of inflammation such as red discoloration of skin and a higher local skin temperature (Spitz et al., 2006, p. 747). Second-degree burns can exhibit the traits of first-degree burns and, in addition, feature blisters as well as the destruction of the top most layers of the skin. The more serious third-degree burns include damage to both epidermis and the dermis with pain less intense due to the fact that the injuries sustained result in destruction of nerve endings present in the skin tissue. Third degree burns leave scars after the injury has healed. After third degree burns, charring occurs. Charring is defined as the obliteration of skin and tissues, and can include damage to the bone (Spitz et al., 2006).
Thermal injuries are affected by varying levels of thermal temperature and by the amount of time a victim is exposed to such extreme temperatures. There is a great difference in the temperature of fires, and this difference depends on the kind of fire. Chemical fires are noted for causing extreme temperatures and, therefore, for rapidly causing the more destructive kinds of thermal injury. Chemical fires can exhibit temperatures of a few thousand degrees Fahrenheit, while standard house fires normally top out at around 1200 degrees Fahrenheit (Spitz et al., 2006, p. 747). The full destruction of the human body resulting in cremation only occurs when a body is exposed to temperatures of nearly 2000 degrees for a period of up to two hours, meaning that common causes of death by thermal injury are almost certain to occur before such a point in the case of a common house fire (Spitz et al., 2006). Thermal injuries can also occur as a result of radiant heat, radiation, and contact with electricity.
Radiant burns occur as a result of exposure to the body of intense light, such as an electromagnetic wave. Radiant heat can come in varying forms and temperatures, and a long exposure to relatively low temperature radiant heat will cause the skin to turn brown and rough. Radiant burns do not damage hair on the body, as other types of thermal injuries do. An exception is in the case of prolonged exposure to radiant heat, when hairs will become singed and, ultimately, destroyed. If exposure to radiant heat is prolonged over a period of time at a sufficiently high temperature, the injuries will include charring. Higher radiant temperatures cause thermal injuries in only a few seconds. One study concluded that a radiant temperature of 1500 degrees will result in a second degree thermal injury in fewer than 10 milliseconds (Di Maio & Dana, 2007, p. 368).
Thermal injuries from chemical fires vary depending on the kind of chemical and the amount of that chemical that are present, as well as the duration of bodily exposure to the fire. A chemical fire can become less intense due to dilution by water and thus result in injuries that are less serious than they would be otherwise. Some acids are responsible for some of the more serious thermal injuries by chemical fire, and these include hydrochloric and sulfuric acids among others (Payne-James, Busuttil, & Smock, 2003, p. 186). Chemicals cause thermal injuries from the direct contact of the chemical with body tissue. Tissue damage can also be more or less severe depending on the chemical agent that has come into contact with the skin and other tissues. Thermal injuries from chemicals are unique in that chemicals continue to damage bodily tissues until the chemicals have been neutralized by the appropriate neutralizing agent. Chemicals cause bodily proteins to coagulate through the processes of oxidation, formation of salt, corrosion, protoplasmic poisoning as well as metabolic competition and desiccation (Di Maio & Dana, 2007, p. 383). Alkali chemicals can cause more severe injuries due the fact that they dissolve proteins and cause fat to turn to soap, which leads to a more extensive invasion of the tissue and to liquefaction necrosis. Thermal injuries caused by acidic chemicals lead to protein coagulation, which causes coagulation necrosis instead of liquefaction necrosis. Acid chemical burns result in scabs that are usually dry and hard and are second-degree in terms of severity, but third-degree burns can result from prolonged exposure as well. Another indicator of the type of chemical burn sustained by a victim is the color of the scab or eschar, as Nitric acid burns give a yellow scab whereas hydrochloric acid gives a white or gray scar (Di Maio & Dana, 2007, p. 384). A victim who became immersed in a heavy solution of hydrochloric acid, to take an example, showed generalized high tensity as well as gray-brown skin color. Additionally, the victim presented with a serious heavy gastric submucosal hemorrhage as well as pulmonary edema. The autopsy concluded that the victim had died due to burn shock from extensive generalized chemical burn. Such a death can also be attributed to chemical burn due to coagulation necrosis that overtakes all skin tissues. The death investigator can identify a chemical burn by hydrochloric acid in particular by the fact that the chemical causes a more dramatic change of skin color than is normally the case given the severity of the burn (Kozawa et al., 2009).
Thermal injuries from electricity can sometimes result in death. Whether death occurs depends upon the amperage that enters the body. The body will experience tremors when a 5-milliamp current travels through it. A current of between 15 and 17 milliamp will force muscles to contract, and this contraction makes it impossible for the electricity to release from the body. Fifty milliamp currents can result in paralysis of the respiratory system if the current is continually fed into the body for any amount of time, in addition to the contraction of muscles. Electrical current travels through the body from a point of contact and moves through to the point of grounding. The current will seek the shortest passage from contact to grounding point, and this path is often from a hand to a foot or, alternatively, from a hand to the other hand. Fibrillation of the ventricle can occur with a 120-V current combined with 1000 ohms of resistance from the skin if the body is exposed to such a current for five seconds, and this process would result in 120 milliamps of current coursing through the body (DiMaio & Dana, 2007, p. 410).