Decomposition takes place after death. This is the breaking down of body tissues, which can also be affected by the environment. Rigor Mortis is one of the best know changes post mortem, but it is very unreliable. Rigor Mortis is the stiffening of the muscles, caused by the accumulation of certain salts in the muscle fibre. This kicks in about 12 hours after death, and takes another 12 hours to disappear. This can help in the pinpointing of time of death, but it is unreliable.

The rate of decomposition can also be affected by the humidity of the location. If the body is in a damp environment it will decompose quicker, whereas a dry environment slows down the rate of decomposition.

Hypostasis also takes place post mortem. This happens because the blood stops circulating the body and so falls to the lowest point. This lividity can be used to determine whether or not a body has been moved from where the person died, or whether their position has been moved.