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Pallor Mortis in which skin becomes pale. It develops 15 minutes after death and is the first postmortem sign of death caused due lack of circulation.
When you watch any zombie movie, you’ll likely notice that the living dead all have pale, nearly grey skin. The English language also has phrases like ‘deathly pale’ to characterize someone’s appearance (like a zombie or a vampire). Besides serving as a linguistic descriptor, changes in skin color do occur after death, a state called Pallor Mortis. It often helps forensic experts evaluate the time of death, which is also called the post-mortem interval (PMI).
What is Pallor Mortis?
The word Pallor Mortis is Latin. Pallor means ‘paleness’ and mortis means ‘of death’. It refers to paleness that develops in a corpse approximately 15 minutes to 2 hours after death. This paleness is more prominent in those with lighter skin tones (especially those with a ruddy complexion), and less so for darker skin types. There are also slight differences in skin color between the two sexes, but this difference disappears as a result of pallor mortis.
Why Does Pallor Mortis Happen?
Pallor Mortis happens due to a lack of capillary circulation.
Clinical death is when the heart stops beating. Without the heart beating, blood cannot reach every part of the body, especially those organs, such as the skin, that are farther away from the heart. The capillaries in the dermis (the second layer of skin after the epidermis) and the hypodermis (the third and deepest layer of the skin) stop receiving a fresh supply of oxygenated blood—and remember, hemoglobin associated with oxygen has a bright red color!
Without the force of the heart pumping blood throughout the body, blood within the blood vessels stagnates and the cells within the blood, like red blood cells (RBCs), move in the direction where gravity is strongest. The areas where blood has moved away will have a pale coloration, whereas those areas where blood has pooled will develop a reddish-pink coloration. The latter phenomenon is called lividity and becomes visible roughly 2 hours after death.
How Do Forensic Experts Use Pallor Mortis to Determine PMI?
The post-mortem interval or ‘time since death’ estimates how much time has elapsed between an individual dying and the body being discovered. Forensic experts back-calculate the time of death using various post-mortem clues.
Pallor Mortis is the first post-mortem stage of death. A paper published in the year 2000 evaluated the usefulness of pallor mortis in determining PMI. The researcher used an octo-electronical color measurement device to measure the color change in 126 corpses. They concluded that since pallor mortis develops rapidly, it isn’t the most useful visible change for determining the approximate time of death. The degree of paleness doesn’t change significantly over time, nor does it offer clues about the cause of death.
Forensic scientists often prefer to use other changes to determine PMI, often using information from more than one factor to estimate a range. They look at how much decomposition has progressed using muscle rigidity (rigor mortis), body temperature, and the presence or absence of certain insects.
Although pallor mortis isn’t of much use to forensic experts, it may be useful if you ever need to spot a zombie in a crowd!