Postmortem Changes: A Forensic Analysis
Cooling of the Body (Algor Mortis)
The cooling of the body after death, known as algor mortis, is influenced by several factors, including poisonings by alcohol, deaths from cold and extreme heat, and acute illnesses. Other factors include:
- Poisonings and Illnesses: Conditions such as alcohol poisoning, convulsive poisonings, heat stroke, and other acute illnesses can affect the body’s temperature regulation and, consequently, the rate of cooling after death.
- Individual Factors: Individual characteristics such as age, height, nutritional status, and weight play a crucial role in determining the rate of heat loss. The circumference of the body is a critical factor, as the speed of cooling depends on the body’s diameter, irrespective of the thickness of adipose tissue.
- Environmental Factors: Four environmental components influence body cooling: radiation, conduction, convection, and evaporation. The body cools off much faster at lower ambient temperatures and higher humidity and ventilation. The time it takes for the body temperature to match the environmental temperature depends more on the difference between body temperature at the time of death and the environmental temperature than on the absolute values of both temperatures. Cooling is more regular and occurs later in the internal organs.
Medicolegal Importance
Algor mortis has two primary applications of forensic interest:
- Diagnosis of Death: A body temperature of 20°C is considered incompatible with life and is thus a sign of certain death. The temperature is typically taken rectally or vaginally.
- Estimation of Time of Death: Thermometry can be very useful in determining the time of death (cronotanatodiagnóstico).
Dehydration (Desiccation)
External environmental conditions characterized by high temperatures and strong ventilation lead to the evaporation of bodily fluids after death. This results in both general and local phenomena.
General Phenomena
- Weight Loss: The weight loss experienced by the body is relatively minor but can be appreciable in newborns and toddlers.
Local Phenomena
- Leathery Skin: The epidermal layer becomes clear, and the skin undergoes a drying process, forming a yellowish, dry, hard, thick, parchment-like area. This area, known as a “plaque of apergaminamiento,” is often traversed by darker-tinted veins.
- Desiccation of Mucous Membranes: This occurs mostly on the lips, causing a reddish-brown or blackish-brown rim on the outermost zone. It can also occur in the transition zone between the skin and mucosa of the vulva in young girls.
- Eye Phenomena:
- Loss of Corneal Transparency: The cornea becomes cloudy within 45 minutes to 24 hours after death.
- Sommer-Larcher Spots: These black spots appear shortly after death, initially as a single spot that extends and becomes rounded or oval, with the base directed toward the cornea. They typically appear first on the outside of the eyeball, with a similar spot appearing on the inside.
- Sinking of the Eyeball: As a result of evaporation from the intraocular fluid, the eyeball becomes loose and soft, ultimately leading to a collapse of the eye area.
Livor Mortis (Hypostasis)
After the cessation of cardiac activity, vascular contraction progresses from the left ventricle to the periphery, emptying the arteries and filling the veins with blood. This blood is then subjected to gravity, accumulating in the dependent parts of the body and producing red-violet spots on the skin’s surface known as livor mortis.
- Intensity: The intensity of livor mortis depends on blood flow. It is more pronounced in cases of asphyxia, where blood does not clot quickly, and less marked in deaths from hemorrhage and anemia due to the smaller amount of blood.
- Distribution: The distribution of livor mortis is determined by the position of the body after death.