Gas can be expelled after death, but it is not the same as a voluntary fart, or flatus, which involves active muscle control. This phenomenon is a natural consequence of decomposition, leading to an involuntary, passive release of accumulated gas.
How Gases Form After Death
Gas production in a deceased body is a direct result of putrefaction, the biological breakdown of the body’s organic matter. This process is initiated by the body’s own vast community of gut bacteria, collectively known as the microbiota. The immune system, which normally keeps these microbes in check, ceases to function at the time of death, allowing the bacteria to spread.
These anaerobic organisms, primarily residing in the large intestine, begin to metabolize the remaining proteins and carbohydrates in the tissues and blood. The main gases produced include methane, hydrogen sulfide, carbon dioxide, and ammonia.
The accumulation of these gases causes noticeable swelling, or bloat, often beginning in the abdomen. Hydrogen sulfide is responsible for the characteristic noxious odor associated with decomposition. This internal gas pressure provides the force necessary to expel the gas from the body’s orifices.
The Passive Release of Post-Mortem Gas
The release of gas after death is entirely a mechanical and passive event. Following death, the body’s muscles enter a period of primary relaxation, which includes the loss of tension in the sphincter muscles. The anal sphincter, which normally controls the release of gas and feces, relaxes, creating a pathway for the internal gases to escape.
As the putrefaction process continues, the sheer volume of gas accumulating in the intestines creates significant pressure within the abdominal cavity. This pressure forces the gas out of the path of least resistance, which can be the relaxed anal or oral sphincter.
The expulsion is often triggered or assisted by external forces, such as gravity or physical manipulation of the remains. For example, moving or lifting a deceased person can compress the abdominal cavity, squeezing the gas out of the body.
Sounds That Are Not Flatus
While intestinal gas expulsion accounts for some post-mortem sounds, other noises are often mistakenly identified as “farting” or “burping.” These sounds are usually caused by the displacement of air that was already present in the lungs at the time of death. Even after the cessation of breathing, a residual volume of air remains trapped within the respiratory system.
When a body is moved, handled, or shifted, the pressure on the chest cavity and diaphragm changes. This external compression forces the trapped air out of the lungs and up through the trachea and larynx.
The movement of this air across the vocal cords or through the respiratory passages creates various sounds, which can range from a sigh or groan to a muffled rush of air. They do not involve the digestive tract or the gases of putrefaction. This displacement of respiratory air is a common observation in forensic science and mortuary settings.