The Five Stages of Human Decomposition
1. Fresh
As soon as the person dies, the body begins to cool. Without blood and oxygen flow, muscular tissues become rigid and blood begins to pool. Bacteria and microbes begin to break down the cells and tissues. At the end of this stage blowflies and flesh flies arrive and lay eggs.
2. Bloat (autolysis)
As bacteria multiply they produce gasses which bloat the body. These gasses build up pressure in the body and push fluids out through natural openings. If insects are present, maggots hatch and feed, resulting in the skin slipping, hair detaching and surface rupturing which creates additional openings for insect activity and bacteria. The gasses and fluids cause the body to give off a strong smell.
3. Active decay (putrefaction)
Insects and bacteria cause loss in body mass. Liquids are released into the surrounding environment. The highest number of insects are present and feed on the fluids. This stage ends when the maggots leave the body.
4. Advanced decay
Most soft tissues have decomposed leaving bones, hair, cartilage, ligaments and some sticky byproducts. Insects able to chew, such as beetles and certain types of flies, arrive and chew on the tougher materials.
5. Skeletonisation
All byproducts of decomposition have dried. Only the skeleton and sometimes the hair is left. Beetles and flies eat any remaining soft materials and mites and moth larvae eat the hair. The bones lighten in colour.
The stages can vary in length depending on conditions such as temperature (generally bodies in warmer environments decay faster), whether the body is buried or exposed to water or air, and the type of bacteria present. Each phase attracts specific insect activity (for example flies first, then beetles) if a body is found within a few weeks the development and age of maggots can be used to estimate the date of death.
