- Clinical science
Exposure to cold, heat, and electrical currents produces characteristic changes in and on the body. Evaluation of these findings allows conclusions to be drawn about the type of damage and when it may have occurred. In the case of exposure to extreme heat, for instance, ante mortem vital signs may be distinguished from post mortem changes. These findings shed light on whether the individual was alive at the time of the fire or already deceased. A typical characteristic of death caused by hypothermia is hemorrhagic necrosis of the gastric mucosa (Wischnewski spots). Death caused by an electric shock may be manifested differently based on the current, voltage, and level of resistance. While a high level of resistance is associated with burns and electrical marks, a lack of characteristic findings is typical in low resistance shock.
In forensic medicine, the search for signs of life is very important in burnt remains to provide evidence of whether the affected individuals were already deceased before the fire (e.g., in homicides in which evidence is destroyed by arson). The detection of ante mortem signs of life can be helpful in such cases.
Signs of life in deceased individuals exposed to fire (ante mortem factors)
Post mortem changes
- heat-related muscle contraction (flexors predominate the extensors) → increased muscle mass on the flexor side :
- Protruding tongue (protrusion)
- Heat hematoma
- Massive heat-related trauma: e.g., cranial burst, heat cracks in the skin
- Burn blisters: do not contain leukocytes or fibrin
For tissue damage caused by burns see .
The following findings indicate death due to hypothermia:
- Bright red livor mortis: indicates delayed intermediary life
- Paradoxical heat sensation: Shortly before drifting into unconsciousness, it is possible that the affected individual experiences a warm sensation. It is not uncommon that bodies are found unclothed.
- Wischnewski spots: hemorrhagic necrosis of the gastric mucosa, which appear as small black discolorations
- Urine analysis: Acetone in the urine may be elevated in cases of hypothermia. The causes are not yet known.
For tissue damage caused by hypothermia see
Unconsciousness occurs once the body temperature drops below 30°C (86°F) . A body temperature below 25°C (86°F) results in rapid death!
- Potentially fatal
- Low voltage: household from 220 V to a maximum of 1,000 V
- Usually fatal
- High voltage : > 1,000 V
Alternating current (household: frequency of 50–60 Hz) is more dangerous than a direct current because ventricular fibrillation can be easily triggered by the alternating voltage!
The current must overcome the skin's resistance to cause damage to the body.
- Dry skin: high resistance
- Moist skin: resistance is reduced by a factor of 10–15
- In water: resistance is reduced by a factor of 25–30
Effect on the body
- Low transitioned current (up to 15 mA): light irritation of the nervous system with a tingling sensation
- From 15 mA: Muscle contractions
- From 50 mA: Ventricular fibrillation is possible.
The smaller the contact point and larger the resistance is, the more likely local heat generation (Joule's first law) and characteristic skin alterations become!
- Electrical marks: white, raised efflorescence with a central depression, which may also occur post mortem
- Fatal in up to 30% of cases; cardiac arrest due to arrhythmias is the most common cause of death
- 70% of survivors have permanent damage (e.g., chronic pain syndromes).
- Lightning strikes can be demonstrated as a cause of death based on the following:
- Lichtenberg figure: branching (fern‑like) patterns on the skin
- Large burns or groups of small burns that appear similar to gunshot wounds
- Scorched hair on the scalp
- Findings on clothing
- Grouped holes in the individual's clothes
- Laceration of leather and shoe soles
- Traces of melting on the body from metal (belt buckles, wrist watches)
- Metalization of the skin: At the point of electrical contact, there is evidence of volatilization and deposition on the skin from metal that was located at the time on the body (evidence via histochemistry or atomic absorption spectrometry).
- Most venomous snake bites occur in developing countries.
- Effects of venom
- Rare medical events; only a few species of spider are harmful
- Most commonly result in a solitary papule, pustule, or wheal
- Systemic manifestations (e.g., respiratory distress, pulmonary edema, hypertension) occur if sufficient amounts of venom enter the circulation.
For management of animal bites, see.