The physical process of death is a sequence of biological events that unfolds in predictable stages, leading to a visible transformation of the body. The appearance of a person changes significantly as the body’s systems shut down, from the hours preceding death to the immediate and later post-mortem periods. These recognizable physical indicators reflect the ultimate cessation of life’s functions.
Physical Signs That Death Is Approaching
In the hours or days before death, the body begins a natural slowing process that produces distinct visual changes. A notable change involves the pattern of respiration, which frequently becomes irregular and is known as Cheyne-Stokes breathing. This pattern is characterized by cycles of increasingly deep and rapid breaths followed by periods where breathing temporarily ceases (apnea), before the cycle repeats. Breathing may also become noisy due to the accumulation of secretions in the throat, sometimes called a “death rattle.”
Circulatory changes become visible as the heart struggles to pump blood effectively, causing a drop in blood pressure. Reduced circulation to the extremities causes the skin to cool and often to develop a marbled or blotchy appearance known as mottling. This discoloration often starts in the hands and feet. As energy reserves deplete, the person spends more time sleeping and becomes less responsive to external stimuli.
The Cessation of Life Functions
The moment of death is defined by the irreversible cessation of the body’s primary life-sustaining functions. This is typically determined by the permanent loss of circulatory and respiratory function, known as cardiorespiratory arrest. When the heart stops beating, blood flow to all organs, including the brain, ceases within seconds. The final breath marks the end of respiration, and the body becomes still.
The loss of circulation quickly leads to the cessation of brain activity, which can be confirmed by a flat electroencephalogram (EEG) in a clinical setting. This sequence marks the transition to the post-mortem phase, characterized by a complete lack of movement and responsiveness.
Immediate Changes After Death
Immediately following the cessation of life functions, rapid physical changes transform the body’s appearance. One of the first changes is pallor mortis, a rapid paleness of the skin that occurs as blood drains from the capillaries. This paleness is noticeable within the first 15 to 30 minutes after the heart stops pumping.
The muscles relax completely in a state called primary flaccidity, causing the jaw to drop and the limbs to become limp. Sphincter muscles also relax, which may lead to the release of urine or gas. The pupils dilate, and the cornea begins to lose its transparency, leading to a cloudy appearance. Body temperature also begins to fall toward the ambient temperature.
The Post-Mortem Indicators
The appearance of the body continues to change over the subsequent hours as three major biological processes develop.
Algor Mortis
Algor mortis, or the cooling of the body, is a steady decline in internal temperature until it matches the surrounding environment. The body generally loses heat at a rate of approximately 1 degree Celsius (1.8 degrees Fahrenheit) per hour. This rate is highly dependent on external factors like air temperature and clothing.
Livor Mortis
Livor mortis, also known as post-mortem lividity, is the purple-red discoloration of the skin resulting from the gravitational settling of blood. Since the heart is no longer circulating blood, red blood cells pool in the capillaries of the lowest-lying areas of the body. This discoloration usually appears between 30 minutes and two hours after death, becoming fully fixed (non-blanchable when pressed) within 8 to 12 hours.
Rigor Mortis
Rigor mortis is the stiffening of the muscles caused by a biochemical change at the cellular level. After death, muscle fibers deplete their supply of adenosine triphosphate (ATP), the molecule necessary for muscles to relax after contraction. Rigor mortis typically begins in smaller muscles, such as the jaw and eyelids, within one to four hours. Stiffness fully develops throughout the body within 6 to 12 hours and gradually disappears over the next 24 to 48 hours as muscle proteins degrade.