An Overview of the Decomposition Process for Bones


When we die, our bodies go through a complex process of decomposition. It’s a natural five-stage process, beginning immediately after death and continuing until nothing is left but a skeleton.

Forensic investigators use the decomposition process to estimate the time since death, called the postmortem interval (PMI). Obtaining an accurate PMI can be beneficial when identifying a victim or determining how they died.

Stage 1: Bloat

The bloated stage is where the body begins to accumulate gaseous materials. This causes the organs in the abdomen to swell, making them appear enlarged.

During this phase of decomposition, the body starts to smell extremely bad. The putrefactive gases produced by the bacteria and microorganisms in the gastrointestinal tract and from the body fluids cause a foul odor that can linger for days after death.

In this stage of decay, postmortem purging occurs where putrefactive body fluids are forced out of body orifices. This also results in the release of fluid from ruptured skin, which is characterized by black discoloration.

Stage 2: Active Decay

During this stage, insects and larvae begin feeding on the body, helping break down soft tissue. As this occurs, the body begins to liquefy, releasing a putrid odor.

Depending on the environment, this stage can take one to a few weeks. Temperature, moisture, and oxygen levels all influence the rate of decay.

Certain insects like H. rostrata, Phoridae adult, and Sylvicola larvae may also accelerate the process.

You may wonder, how long does it take for bones to decompose? Skeletons often disintegrate in fertile soil after 20 years if animals do not remove or shift the bones. Frames can last for hundreds of years in neutral soil or sand.

Stage 3: Advanced Decay

In this stage of decomposition, bacteria, and maggots feast on a body’s flesh. The resulting putrefaction produces gaseous byproducts that cause the skin to bloat and the internal organs to swell.

As a result, the body’s lining becomes opaque, often accompanied by a strong smell of decay. This attracts blowflies, flesh flies, beetles, and mites.

At this stage of decomposition, the majority of soft tissue is gone. Whatever remains is now leathery and dry, and parts of the skeleton can be seen. More giant insects like beetles will come to feed on these tissues, breaking them down as well.

Stage 4: Drying

During this stage, the body’s tissues break down and ferment. This process produces a cheesy-smelling substance that attracts a new suite of corpse organisms.

Insects, primarily grubs and beetles, join bacteria to decompose the remaining tissues and organs. This stage occurs four to 10 days after death.

The body will then begin to dry out and lose its liquid content. This causes the skin to darken and turn greenish, and odoriferous gases will expand in the body cavity. These activities allow scavengers to access the internal organs and break down the flesh.

Stage 5: Skeletalization

When a person dies, their body goes through an organic decomposition process. Many factors, including air moisture and temperature, pH levels, and the cause of death, impact this process.

Once a person dies, their body begins to break down as bacteria invade the soft tissues. Depending on the environment, this can occur quickly or slowly.

During the first stage, called autolysis, excess carbon dioxide causes an acidic environment. This causes membranes of cells to rupture and release enzymes that eat the cell from the inside out.

This stage is called black putrefaction because the released chemicals contain sulfuric compounds and bacteria. This decay phase attracts flies, which feed on the body’s cellular remains.

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