Electrocution Lightning and Radiation Chapter Notes | Forensic Medicine and Toxicology (FMT) - NEET PG PDF Download

Introduction

Physical forces such as electricity, lightning, and radiation can lead to both minor and severe injuries. These forces have recently been categorized as environmental emergencies and are now addressed separately to improve our understanding of the trauma they inflict.

Electrocution

Electrical injuries are common, intricate, and can be very serious, occurring in both industrial and domestic environments. The impact and severity of electrical trauma can vary greatly, from a mild discomfort caused by low-voltage household currents to instant death and severe injury from high-voltage electrocution or lightning strikes. Unlike burns caused by heat, electrical injuries typically affect multiple body systems, making accurate assessment and management difficult.

Electrical injuries can lead to:

• Burns to the skin and deeper tissues
• Disturbances in heart rhythm
• Additional injuries resulting from falls or other accidents

The severity and type of injury depend on various factors, including:

• Amperage
• Voltage
• Type of current (AC vs. DC)
• Duration of contact
• Tissue resistance
• Pathway of current flow through the body

Generally, higher voltage, greater current, longer contact time, and current passing through the heart lead to more severe injuries and poorer outcomes. Lightning strikes can cause the most extreme electrical injuries.

When a substantial electrical current passes through the body, it can cause skin damage, organ failure, or even death. This phenomenon is known as electrocution, and most fatalities are accidental, occurring in homes or workplaces.

Electricity can be produced naturally, as in the case of lightning, or artificially, as in the case of electric current. There are two primary types of artificially generated electric currents:

• Direct current (DC) flows continuously in one direction and is generally less hazardous (200-250 milliamp intensity can be lethal). High-amperage DC (above 4 A) might even restore normal heart rhythm, similar to medical defibrillation.
• Alternating current (AC) changes direction rapidly and is more dangerous (70-80 milliamp intensity can be lethal) because it causes muscle spasms, preventing the victim from releasing the live wire. AC is also more likely to cause serious heart problems like ventricular fibrillation.

Fatal Electrocution Events

In cases of fatal electrocution, three primary life-threatening scenarios can occur:

• The most prevalent scenario involves current passing through the heart when a hand comes into contact with a live wire, completing the circuit. Contact with the right hand and exit through the feet is particularly hazardous, as it runs along the heart’s axis, often leading to deadly cardiac arrhythmias, typically ending in asystole.
• In less frequent cases, current may pass across the chest and abdomen, causing respiratory failure due to muscle spasms.
• Rarely, current may flow through the head and neck, especially if a worker’s head contacts a live wire, potentially affecting the brainstem and paralyzing essential functions.

It is often believed that individuals can develop a tolerance to electric shock, and electricians sometimes work with live wires without experiencing harm. However, it is more likely that their expectation of shocks diminishes sensitivity, but only for brief contacts that are less likely to cause significant damage.

Effects Due to Passage of Electricity

The effects of electric current on the human body can be categorized into two types:

Local Effects

• Burns and Blisters: These occur on the skin and are referred to as cutaneous electrical marks. The term "Joule burn" is used for this type of injury, which happens when electrical energy is converted into heat within the body. This is different from exogenous burns caused by an external heat source.
• If the skin is moist and comes into contact with a conductor wire or a faulty electrical appliance, visible burns may not be present. However, dry skin is more likely to exhibit clear electrical burns.
• The edges of the burn may appear puckered, without a red line or reddening at the entry point (such as hands or fingers) or the exit point (like the opposite hand or feet).
• In some cases, the shape of the object causing the electrocution may be visible, creating a patterned electric mark. This can help in understanding the circumstances of the injury or determining the cause of death in cases of unwitnessed electrocution.

Contusions and Lacerations:

• The wounds may be lacerated and punctured, with contusions around their edges.
• The current exits through the bare sole of the foot, which may become hard and thick, leading to deep laceration-like damage. Hair may also be singed, and clothing can be burned at the site.

Metallisation of Electrical Marks:

• When current flows from a metal conductor into the body, electrolysis occurs, embedding metallic ions in the skin and subcutaneous tissues. This can happen with both alternating current (AC) and direct current (DC) due to the combination of metallic ions with tissue anions to form metallic salts.
• Although these metallisations are usually invisible, they can be detected using chemical, histochemical, and spectrographic methods. They can persist for weeks in a living person and resist some changes after death. Recent electron microscopy has revealed these metallisations as tiny metal globules on the skin at or near electric marks.

Micropathological Skin Changes at the Electrocution Site:

• These changes essentially represent an electrical burn. Local lesions are commonly found on the hands or fingers at the entry and exit points of electric current, usually more severe on the feet or opposite hands.
• The following microscopic changes are typically observed:
• Compression of the horny layer into a uniform plaque with flattening of the underlying papillary processes.
• Fissures and hollows may form between the stratum corneum and germinativum.
• Basal cell changes are a clear indicator of electrocution, with basal cells merging into star-shaped or rod-like structures in each group of the rete malpighii.
• Charring and vacuolation in deeper epidermal and dermal cells occur due to gas spaces from heated tissue fluids that separate the cells.
• Metallisation in the skin may show fine metallic particles from the conductor substance in some cells.
• Epidermal nuclei appear pyknotic, elongated, and arranged in a parallel or palisading pattern, often referred to as "nuclear streaming."

Flash or Spark Burns:

• High tension currents can jump several millimeters through the air, causing injuries. For example, in dry air, a current of 100 kV can leap up to 35 mm.
• These currents generate extremely high temperatures (up to 4000°C), similar to the spark plug of a petrol engine.
• The intense heat from an electrical flash can create burns that resemble thermal burns over large areas and can cause the keratin in the skin to melt in various spots.
• This molten keratin solidifies into hard brownish nodules as it cools, resembling crocodile skin.

Crocodile Skin Lesion:

• The term “ crocodile skin. lesion was introduced to describe a specific type of skin damage caused by electrical burns.
• This lesion is characterized by multiple areas of damage that resemble the skin of a crocodile.
• These lesions are commonly found in areas where a limb bends excessively, such as joints.
• When the electric current passes through the body, it travels across the joints instead of around them, leading to these distinctive lesions.

Constitutional Effects
Individuals affected by electrical injuries may experience various constitutional effects depending on the severity of the current.

• Momentary Shock: If the current is low, individuals may experience momentary shock but can fully recover.
• Stunned State: Victims may become stunned or enter a state of suspended animation.
• Neurological Impairments: Survivors may experience neurological impairments such as hemiplegia (paralysis on one side of the body), paraplegia (paralysis of the lower body), and loss of sight, hearing, or speech.
• Immediate Death: In some cases, immediate death can occur if the current is fatal.
• Worsening Factors: Factors such as alternating current,wet clothing,poor health, and anxiety can exacerbate the effects of electrical injuries.

Causes of Death

• The primary cause of death from electrocution is ventricular fibrillation, particularly in cases involving low voltage current. This condition leads to cardiac arrest when the electrical current passes through the heart muscle, especially affecting the outer layers.
• The electrical current significantly disrupts the heart's electrical system, but the exact effects on the heart's pacemaker and conduction pathways are not fully understood.
• A recent study discovered that myofibre break-up (MFB) is present in 90% of electrocution deaths, indicating a unique change that occurs before death. MFB is consistently observed in all cases of electrocution.
• Myofibre break-up (MFB) involves various histological patterns, including:
  • Swollen bundles of heart cells adjacent to overly contracted cells, some of which have ruptured intercalated discs.
  • Overly contracted heart cells alternating with stretched cells, often separated by widened discs.
  • Non-eosinophilic bands of overly contracted sarcomeres alternating with stretched sarcomeres.
• Recognizing MFB is crucial for determining the cause of death in autopsy cases where the cause is unclear, especially when there are no obvious findings despite a history of electrocution.
• In cases of high voltage electrocution, another cause of death is the inhibition of the respiratory center. This occurs when the electrical current affects the muscles responsible for breathing, leading to respiratory paralysis or spasms.
• When the current passes through the chest, it can impede breathing, resulting in congestive-hypoxic death. Typically, the brain stem remains unaffected, but damage can occur if the current enters through the head, potentially leading to cardiac arrest or respiratory failure.
• It is also important to acknowledge that non-electrical causes, such as falls from height, can contribute to fatalities in electrocution victims.

Medicolegal Considerations

• Electrocution deaths are typically accidental, but suicides and homicides have also been documented. Bathrooms are a frequent location for such incidents due to the high risk of electric shock. Electrical suicides have recently increased, particularly in Germany, while homicides involving electricity, though rare, have been reported in the United States. Additionally, electricity is used as a method of judicial execution in some U.S. states, including Alabama, Florida, Georgia, Kentucky, Nebraska, and Tennessee.
• In judicial electrocution, the condemned individual is secured to a wooden chair with electrodes placed on a shaved scalp (via a helmet) and the right lower leg. An initial high-voltage surge of 2,000–2,400 volts is applied for about seven seconds, causing immediate unconsciousness. A second, lower-voltage surge of 500–600 volts, lasting 17 seconds to one minute, delivers the fatal effect. The process may be repeated, and after five minutes, a physician checks for a heartbeat. If the heart is still beating, another surge is administered. The first recorded judicial electrocution was William Kemmler on August 6, 1890, at New York’s Auburn Prison. During electrocution, skin temperature under the electrodes can reach 60°C, with the brain reaching similar temperatures. Microscopic examination may reveal ruptured neuroaxons and blood vessels in the brain. The right leg often exhibits cadaveric spasm, and ejaculation may occur at the time of death.
• In cases of electrocution involving a wet body surface, visible signs may be absent, making autopsy findings inconclusive.

Execution by Electrocution in Electric Chair

• Electrocution was introduced in New York in 1888 as a supposedly more humane method of execution compared to hanging.
• However, there have been gruesome incidents where inmates have caught fire, required multiple electric jolts to die, and suffered broken bones due to violent convulsions.
• In the United States, the electric chair is still an option for those convicted of crimes before 1999, when lethal injection became the primary method of execution.
• Since the US Supreme Court reinstated the death penalty by electrocution in 1976, several inmates have been executed in the electric chair. The last known execution of this kind was in Virginia in July 2006.

Lightning and Its Injuries

Lightning is similar to ordinary electric currents but operates on a much larger scale. It occurs when a thundercloud's charged undersurface, typically negatively charged, discharges electricity to the ground. About 5% of lightning flashes carry a positive charge, often observed in mountainous areas. A single lightning bolt can carry over 1,000 million volts, releasing significant energy, primarily as heat, along its path.

Five mechanisms of lightning injury are recognized: direct strike, contact, side flash, ground current, and upward streamer. Mechanical injuries may also occur due to falls or muscle contractions caused by the strike.

Mechanisms of Lightning Injury

1. Direct Strike: The lightning bolt directly hits the victim, causing severe injury.

2. Contact/Conduction: The victim is injured by touching an object struck by lightning, indirectly receiving the electrical charge.

3. Side Flash: Lightning strikes an object (e.g., a tree) and jumps to a nearby person. The current may spread over the body’s surface, enter the body, or both, especially if the person is close to the struck object.

4. Ground Current: After lightning strikes a person, the electrical energy flows through the body toward the ground, causing injuries.

5. Upward Streamer: This occurs when a thundercloud’s electric field induces charges in objects protruding from the ground, such as a flag or a person. For example, lightning may strike a tall crane, with the current flowing through its metal structure to injure a worker touching it, similar to contact with a high-power electrical line.

Lightning and Lightning injuries

In most cases observed during autopsies, the current spreads over the body’s surface and enters it, often resulting in torn clothing, burst shoes, singed hair, burns from heated metal objects (e.g., zippers), and distinct entrance and exit wounds. Ruptured tympanic membranes are also common. Lightning victims with such injuries are sometimes mistaken for hit-and-run victims due to the appearance of torn clothing and other trauma.

Regarding upward streamers, not all connect with downward leaders to form a complete lightning channel. Weak upward streamers, ranging from 10 to 400 amps, can still impair bodily functions despite their lower magnitude and short duration. These currents may cause subtle effects rather than severe physical damage.

Lightning While in an Automobile/Using Telephone/ I-pod Music System

• When inside a metal vehicle such as a car, bus, truck, or train, the risk of being harmed by lightning is very low.
• There have been very rare instances of injury or death when using a telephone that gets struck by lightning, but this is not common.
• Another unusual case involves injuries to the ear and face from lightning while listening to music on an iPod.

Causes of Death from Lightning Strikes

• Immediate death from a lightning strike is typically due to high-voltage direct current.
• Lightning-related deaths can result from:
  • Syncope (temporary loss of consciousness)
  • Cardiopulmonary arrest (heart and respiratory failure)
  • Electrothermal trauma (burns from electrical and thermal energy)
  • Paralysis of the nervous system
• In some cases, death can be delayed in lightning victims, often due to complications from burns.
• If someone survives a close lightning strike, they may still be okay, as many lightning victims do survive.

Postmortem Characteristics of Lightning-Induced Fatalities

This section encompasses observations related to the body and the clothing worn at the time of death. The findings pertaining to the body are categorized into external and internal observations.

External Findings

• Ecchymosed Burns: These burns, caused by fused metallic substances, can vary in degree and are typically observed on the body.
• Arborescent Markings: Also referred to as filigree burns or lightning prints, these injuries manifest as fern-like patterns on the skin. They are characteristic of lightning injuries and appear as temporarily reddened areas shortly after the incident, fading within 24 hours. These markings are believed to result from positive discharges over the skin.
• Mechanisms of Arborescent Markings:
  • Negative Lightning Strike: These markings may occur when a person is struck by a negative lightning bolt and subsequently affected by a secondary positive flashover from a nearby grounded object.
  • Positive Lightning Strike: Alternatively, they could represent an entrance point for individuals struck by a positively charged lightning bolt.
  • Historical Explanation: Some suggest that these markings result from copper deposition on the skin and tissue staining due to haemoglobin released from damaged red blood cells along the electric current's path.
• Clarification on Arborescent Lesions: It is crucial to understand that these markings are not lesions caused by burns. The various explanations, none of which are mutually exclusive, help elucidate the rarity of arborescent lesions in individuals struck by lightning.

Internal Injuries

• Congested Membranes: The membranes inside the body are often swollen and may have lacerations or cuts.
• Intracranial and Intracerebral Effusion: There is an accumulation of blood in the cranial (skull) and cerebral (brain) areas.
• Patchy Hemorrhage: There are irregular spots of bleeding on the pleura (the membrane surrounding the lungs) and lung surface.
• Petechiae: Severe disruption can lead to widespread tiny red or purple spots caused by bleeding under the skin, known as petechiae.

Findings on Clothing

• Burnt Clothing: At the entry and exit points where lightning has struck, the clothes are often burnt. The clothing is usually torn, and shoes may also burst open.
• Fused Metallic Articles: Nearby, there may be fused metallic articles, indicating the intense heat from the lightning.

Medicolegal Aspects

• Accidental Deaths: Most deaths caused by lightning are considered accidental rather than intentional.
• Thunderstorms: Thunderstorms are often present in the area where the incident occurred.
• Fused Metallic Substances: Fused metallic substances might be found nearby, and the body may show no visible wounds.
• Evidence of Lightning Damage: Signs of damage from lightning in the area can support the diagnosis of accidental death.

Radiation

Radiation exposure can occur in two primary ways:

• The first way is through a strong radioactive source, such as uranium.
• The second way is through contamination by dust, debris, and fluids that contain radioactive material.

Factors that Determine the Severity of Exposure

• The duration of exposure.
• The distance from the radioactive source.
• Shielding from radiation.

Types of Radiation Exposure

The three types of radiation exposure are:

• Alpha
• Beta
• Gamma: This is the most severe type of exposure due to its high penetrating ability.

Effects of Radiation

• Radiation exposure generally does not result in immediate side effects unless the exposure is severe.
• Most serious health issues tend to manifest years after the exposure has occurred.
• Acute symptoms that may arise include nausea, vomiting, and malaise.
• Severe exposure to beta or gamma radiation can result in burns, serious illness, and even death.

In the present day, individuals are exposed to radiation from various sources, which can be categorized into two types:

• Ionising radiation
• Non-ionising radiation, which includes UV rays, visible light, infrared rays, and microwaves.

Ionising Radiation (IR)

Ionising Radiation (IR) has the potential to cause radiation injury by damaging the atoms and molecules within a substance, which subsequently harms the body. When IR passes through a living cell, it can injure the cell by disrupting its chemical structure, leading to severe damage, loss of function, and ultimately cell death. Cells in rapidly growing tissues are particularly vulnerable to radiation. For example:

• Bone marrow cells, found in the centre of bones, are among the fastest-growing structures in the human body and are often the first to be affected by ionising radiation.

Ionising Radiation can manifest as electromagnetic waves and is commonly emitted by sources such as:

• The Sun
• X-ray machines
• Radioactive elements

Sources of Ionizing Radiation (IR) Harmful to Human Health

Humans encounter ionizing radiation (IR) from various sources, which can be categorized into four main types:

• Natural
• Intentional
• Accidental
• Therapeutic

Natural Sources of Ionizing Radiation
Natural sources of ionizing radiation are responsible for only a small number of radiation injuries. These sources include:

• Sunlight: The ultraviolet (UV) rays emitted by the sun contain ionizing radiation.
• Cosmic Radiation: Cosmic radiation is constantly present in our environment and contributes to our exposure to ionizing radiation.

When a person goes outside, they are exposed to ionizing radiation from sunlight. Similarly, cosmic rays, like sunlight, are not visible, but they also contain ionizing radiation.

Intentional Exposure
Intentional exposure to ionising radiation (IR) is extremely rare and occurs in specific circumstances, such as the use of nuclear weapons in warfare. The most notable instances of intentional exposure to IR happened during World War II when the United States dropped atomic bombs on the cities of Hiroshima and Nagasaki in Japan. These tragic events resulted in the deaths and injuries of countless individuals and mark the only cases in history of intentional exposure to IR.

Accidental Exposure
Accidental exposure to ionising radiation occurs when individuals inadvertently come into contact with radioactive materials. This can happen in various situations, such as:

• Research laboratory spillage: In research laboratories, radioactive materials can sometimes spill, leading to potential exposure for workers handling these substances.
• Nuclear reactor accidents: Between 1945 and 1987, there were numerous nuclear reactor accidents worldwide, resulting in injuries and fatalities. For instance, the Chernobyl Nuclear Reactor accident is a well-known incident where individuals continue to suffer from the long-term effects of radiation exposure due to the accident.

Therapeutic Exposure to Ionising Radiation

• Medical Procedures: Therapeutic exposure to ionising radiation occurs during various medical procedures where radioactive elements are used for diagnostic and therapeutic purposes.
• Diagnostic Imaging: Radioactive tracers are administered to patients for diagnostic imaging, helping to identify and monitor various medical conditions.
• Cancer Treatment: Ionising radiation is used in cancer treatment, often through external beam therapy with radioactive cobalt (supervoltage therapy).
• Therapeutic Doses: Therapeutic doses of radiation are generally considered safe, but they can cause skin reactions at the site of application, such as skin depletion, erythema (redness), blistering, and discolouration over time.
• Industrial Applications: Radioactive substances are utilised in various industries such as watchmaking, pharmaceuticals, and chemical analysis.
• Military Use: Nuclear weapons employed by superpowers can cause mechanical trauma, burns, and radiation sickness due to ionising radiation.
• Action Mechanism: Ionising radiation alters the chemical structure of various enzyme systems, and developing fetuses and children are more susceptible to these changes.
• Hematological Changes: Doses above 50 to 100 rads increase the likelihood of hematological changes and disabilities.
• Sensitivity of Tissues: Hematopoietic cells, Peyer’s patches in the small intestine, germinal epithelium of the testis, and cornea are more sensitive to ionising radiation compared to musculoskeletal tissues.

Medicolegal Aspect

• Responsibility of Doctors: Doctors administering supervoltage therapy must exercise caution, as patients can sue for negligence if harm occurs.
• Safety Precautions: When dealing with radioactivity exceeding 5 millicuries, safety measures such as wearing rubber gloves, plastic aprons, safety goggles, and plastic shoe covers are necessary.
• Ultraviolet Burns: Burns caused by ultraviolet rays can lead to skin reactions like erythema and eczematous responses.