Lividity, also known as livor mortis, is a reddish-purple discoloration of the skin that appears after death. It provides information about the body’s post-mortem state.
What is Lividity?
Livor mortis is the settling of blood in capillaries and veins due to gravity after the heart stops circulating it. Without the heart’s pumping action, red blood cells sink through the plasma, leading to purplish-red discoloration in the body’s lowest areas.
Discoloration does not occur where capillaries are compressed, such as areas in contact with a firm surface or tight clothing. This creates “contact pallor” where the skin remains uncolored. The color’s intensity depends on the amount of reduced hemoglobin in the blood.
The Timeline of Lividity
Lividity begins to develop shortly after circulation ceases, with initial signs appearing within 20 to 30 minutes. The discoloration starts as faint, patchy red areas that gradually increase in size and intensity over the next few hours.
Initially, pooled blood can be pushed away by pressure, causing the discolored area to temporarily blanch. This indicates lividity is not yet fixed. As time progresses, typically between 6 to 8 hours after death, blood begins to coagulate in the vessels.
Lividity becomes “fixed” when blood cells break down and stain surrounding tissues. This makes the discoloration permanent, meaning pressing on the skin will no longer cause it to blanch. Maximum lividity occurs between eight and twelve hours after death, at which point it is considered fixed.
Factors Affecting Lividity
Several factors can influence the appearance, intensity, and fixation time of lividity. Ambient temperature plays a role, with colder conditions potentially slowing the development and warmer conditions accelerating it. The volume of blood in the body also affects lividity; for instance, individuals with severe hemorrhage or anemia may show less intense or delayed discoloration.
The body’s position after death directly determines where the blood pools due to gravity. For example, if a person dies lying on their back, lividity will be most apparent on the backside, excluding pressure points. Certain causes of death can also affect the color of lividity, such as carbon monoxide poisoning, which can result in a distinctive cherry-red discoloration due to the presence of carboxyhemoglobin.
Why Fixed Lividity Matters
Fixed lividity provides information in death investigations, particularly for estimating the post-mortem interval, the time elapsed since death. The stage of lividity, whether blanching or fixed, helps forensic professionals establish a general timeframe. While not an exact measure, it is used with other post-mortem changes to narrow the estimate.
Fixed lividity indicates whether a body has been moved after death. If the pattern of fixed lividity does not align with the final position, it suggests the body was repositioned after blood permanently settled and stained tissues. For example, a body found on its side with fixed lividity on its back indicates it was originally supine for several hours before being moved.