Cadaveric Lividity and Rigor Mortis: A Forensic Analysis
Cadaveric Lividity
Cadaveric lividity depends on the position of the cadaver. When the body is supine (face up), the spots form on the entire dorsal surface, except where pressure is applied. If the body is prone (face down), the lividity appears on the front of the body, respecting pressure areas. As a rule, lividity is located in the dependent regions of the body, indicating the position in which the body remained.
Varieties of Lividity
Hypostatic purple lividity consists of point-like scarlet fever. It is caused by the rupture of vessels due to increased intravascular pressure, especially if the capillary walls undergo fatty degeneration. Paradoxical lividity is observed in supine cadavers, with lividity in the face, anterior neck, and chest regions, often associated with sudden or asphyxial deaths.
Evolution of Cadaveric Lividity
Lividity starts as small, isolated patches that gradually merge to encompass larger areas. The spots begin to appear shortly after death. In a supine position, the first appearance is in the back of the neck region. In the rest of the body, it appears 3 to 5 hours after death and occupies the lower levels of the body. At 10 to 12 hours after death, the shape or color will not change until decomposition begins.
Transposition of Lividity
It is possible to displace lividity for some time after its recent formation. Cadaverous pallor can be erased by pressing hard with a thumb or resistant glass on a limited point of its surface, changing the cadaver’s position. Over time, these maneuvers become ineffective. The process of fixing lividity becomes permanent after 10 to 12 hours. It is possible to find a corpse with lividity at two different levels or even opposite sides when changing the body position after the fixing process has begun.
Differential Diagnosis
Differentiate cadaveric lividity from ecchymosis. Ecchymosis involves extravasated blood, congealed and firmly adhered to the mesh of the tissue, while lividity does not involve extravasated blood.
Medicolegal Importance
- Diagnosis of death: Cadaveric lividity has great value as a sign of death when it is large, intensely colored, and typically localized, occurring 12 to 15 hours after death.
- Determining the time of death: The time of onset of lividity, the cost of acquiring its full extent, and the possibility of transposition are other criteria for chronological diagnosis.
- Position of the corpse: The topographic location of lividity represents a true testament to the position in which the body remained after death. Of particular importance is the finding that the lividity has an abnormal relation to the position in which the body was found, especially if they are in opposite planes, indicating a transposition after 12 hours of death and within 24 hours.
Rigor Mortis
After some time, usually brief, a slow process of muscular contraction begins, known as rigor mortis. It is a constant phenomenon, varying only in the time it takes to set in, which can be exceptionally early or late.
Evolution
Rigor mortis is variable and appears first in the smooth muscle fiber, myocardium, and diaphragm, and slightly later in skeletal muscles. It usually initiates 3 to 6 hours after death, or even before, starting in the…