“Decomp” is shorthand for decomposition, the natural biological process by which a body breaks down after death. It’s the most common use of the term, especially in forensic, criminal justice, and true-crime contexts. The word can also refer to decompensation (when an organ like the heart fails to compensate for disease) or decompression (the pressure changes divers experience). This article covers all three meanings, starting with the one most people are looking for.
Decomposition: The Five Stages
After death, the body moves through five recognized stages of decomposition: fresh, bloat, active decay, advanced decay, and dry remains (also called skeletonization). These stages overlap and their timing varies enormously depending on the environment, but the sequence is consistent.
The fresh stage begins immediately after death. The body’s own enzymes start digesting cells from the inside out, a process called autolysis. During this window, the body cools to match its surroundings, blood pools in the lowest parts of the body creating purple-red discoloration, and muscles stiffen.
The bloat stage typically becomes visible 24 to 48 hours after death. Bacteria in the gut, no longer held in check by the immune system, begin producing gases that cause the abdomen to swell. The swelling spreads to the face and extremities. Blood vessels become visible through the skin as greenish-black streaks, a pattern called marbling. Blisters form, and the outer layer of skin starts to loosen and slip off.
During active decay, the bloating ruptures and fluids are forced out of the body’s openings. Hair detaches. Skin darkens and breaks apart. This is the stage that produces the strongest odor, as bacteria release a complex mix of volatile chemicals. Among the best-known are cadaverine and putrescine, two nitrogen-containing compounds that have long been associated with the smell of death, though research has shown they are just a small part of a much larger chemical signature. A 2015 study identified a combination of eight specific compounds, including sulfur-containing molecules and certain esters, that appear unique to human and pig decomposition.
Advanced decay is sometimes called black putrefaction. Bones start to become exposed, and the body takes on a collapsed, caved-in appearance. Tough tissues like cartilage and hair persist longer than soft tissue, but most of the body’s mass is gone.
The dry remains stage begins when bone is extensively exposed but hasn’t yet broken down. Only dried skin, cartilage, and tendons remain. Decomposition slows dramatically at this point. It can take years or even decades for skeletal remains to fully disintegrate.
What Speeds Up or Slows Down Decay
Temperature is the single most important factor. Forensic scientists use a measurement called accumulated degree days (ADD) to estimate how long someone has been dead. ADD combines elapsed time with temperature to calculate how much thermal energy has driven the chemical reactions of decay. A body in a hot climate can reach skeletonization in weeks; in cold or freezing conditions, the process stalls almost entirely.
Where the body is located matters just as much. A longstanding forensic rule of thumb known as Casper’s dictum holds that a body decomposes in open air twice as fast as one submerged in water, and eight times as fast as one buried in earth. Soil insulates the body and limits insect access, while air exposure maximizes both heat and the arrival of scavengers.
Humidity, clothing, body size, and cause of death all play secondary roles. A body with open wounds decomposes faster because bacteria and insects gain easier access to tissue.
How Insects Help Estimate Time of Death
Blowflies (family Calliphoridae) are almost always the first insects to arrive. In warm weather, they can appear within minutes and begin laying eggs immediately. Their larvae, or maggots, are the primary drivers of soft tissue removal during active decay. In cooler months, the same flies may take weeks to appear and are slower to reproduce.
As decomposition progresses, different species arrive in a predictable sequence. Blowflies dominate the early stages. Beetles, particularly rove beetles and carrion beetles, arrive later. In the final dry stages, skin beetles (Dermestidae) feed on remaining dried tissue. By identifying which insects are present and how far along their life cycles have progressed, forensic entomologists can estimate the minimum time since death. This approach is one of the most widely accepted methods for establishing a postmortem interval, especially when other evidence is limited.
Decomp as Medical Shorthand: Decompensation
In hospitals, “decomp” often refers to decompensation, particularly decompensated heart failure. This is a clinical syndrome in which the heart can no longer pump or fill with blood effectively enough to meet the body’s needs. For a long time, the heart may compensate for underlying damage by beating faster, thickening its walls, or relying on hormonal signals to maintain blood pressure. Decompensation is the point where those workarounds fail.
The result is a rapid worsening of symptoms: severe shortness of breath, fluid buildup in the lungs and legs, fatigue, and an inability to perform basic activities. It’s a medical emergency. The term also applies to liver disease (decompensated cirrhosis), where the liver can no longer manage its essential functions, leading to fluid in the abdomen, confusion from toxin buildup, and internal bleeding.
If you see “decomp” in a medical chart or hear it in a hospital setting, it almost always means a patient whose body has lost the ability to compensate for an existing condition.
Decomp in Diving: Decompression Sickness
Divers sometimes use “decomp” to refer to decompression, the process of returning to normal atmospheric pressure after a deep dive. When a diver descends, the increased water pressure forces nitrogen from their breathing gas into body tissues. At depth, this dissolved nitrogen causes no problems. The danger comes from surfacing too quickly.
A rapid ascent causes the dissolved nitrogen to form bubbles in the blood and tissues, much like opening a carbonated drink. These bubbles can block blood vessels, trigger inflammation, and damage tissue throughout the body. This is decompression sickness, commonly called “the bends.” Symptoms range from joint pain and skin rashes to numbness, paralysis, and life-threatening cardiovascular collapse, depending on where the bubbles form.
The solution is controlled ascent. A slow rise to the surface allows nitrogen to leave the tissues gradually in its gaseous form, passing safely through the lungs and out with each breath. Dive tables and dive computers exist specifically to calculate safe ascent rates and required decompression stops at various depths.