Upon death, the body begins a radical chemical metamorphosis. A typical smell emerges. Explanations from forensic doctor Michel Sapanet.
Death is often perceived as a T moment, an immediate change. Yet, to science and forensics, it looks more like a slow lights-out. This complex biological process is accompanied by a very particular olfactory signature which evolves throughout the stages of decomposition. Dr Michel Sapanet, director of the Poitou-Charentes Institute of Legal Medicine, helps us decipher this little-known phenomenon.
Death leads to a cessation of vital functions (breathing, circulation, neuronal communication). This marks the beginning of physical degradation. Dr Sapanet specifies that the speed of this process varies: “What happens after death depends enormously on the causes of death and the conditions in which the body is preserved“Deprived of oxygen and an active immune system, the body becomes the playground of bacteria, especially those that naturally reside in our digestive system. This is the beginning of the cycle of putrefaction.
The tissues transform and the visual appearance of the body changes radically. “The body begins to ooze black and red fluids, the skin gradually turns greenish then black and the body gives off very unpleasant odors. In a person with a significant excess fat, the fat will liquefy and large bubbles will appear on the surface of the skin with putrefactive liquids or liquefied fat inside.“.
The first hours following death, the smell is relatively discreet. Dr Sapanet compares it to that of “cold meat”. It smells like animal tissue that no longer benefits from metabolic heat or circulation. The more decomposition progresses, the more the proteins break down. “This smell will evolve and tend towards a characteristic smell of certain strong cheeses such as Époisses or Maroilles. During decomposition, the body’s proteins undergo the same type of transformation as the proteins in certain cheeses.“As fat breaks down, it releases volatile fatty acids.”They emit a smell of rancid butter. Bones, even when cleaned, also retain that rancid butter smell.“, describes the forensic doctor.
If this smell causes such visceral repulsion in us, it is because it instantly activates the amygdala, the fear center in our brain. This is an ancestral survival mechanism: our instinct alerts us to a biological danger (bacteria, toxins) and tells us to move away from the source of contamination.
The smell of death is the result of biological recycling. If it instinctively repels us, it testifies to the relentless transformation of organic matter. Between the breakdown of proteins and the acidity of rancid fats, the human body eventually returns to its basic chemical components.
Thanks to Dr Michel Sapanet. Comments collected in 2022.
