Post-Mortem Lividity
Post-mortem lividity, also known as hypostasis, is the staining visible on the skin of a dead body, this happens when gravity causes the blood to settle after death This occurs across the entire lower side of the body but in places where parts of the body are in contact with a solid object, such as the floor, the flesh compresses and staining does not occur in that area although blanching can be visible. It is recognisable by its distinctive reddish-purple, or sometimes blueish-purple, colouring and is usually visible within an hour of death but more pronounced around 4 hours after death. Within the first 4 hours, these stains are not fixed and if the body is moved the blood will shift and stain the part of the body that becomes lower. Depending on the conditions the body is kept in, these stains become fixed between 8 and 24 hours after death.
Post-mortem lividity can be useful for murder investigations as it can indicate how the body was left, for example, if the stains are not at the lowest part of the body it can indicate the body has been moved after the 8-24 hour staining period.