Livor mortis

Livor mortis is one of the early changes after death. Once the heart stops, blood no longer circulates, and gravity draws it into the small vessels of the lowest parts of the body, staining the skin there purplish red. In a body lying on its back, lividity develops along the back of the neck, trunk and limbs but not where skin presses against the surface beneath, such as the shoulder blades and buttocks; these pale zones are called contact pallor. Tight clothing leaves similar pale bands.

Lividity usually becomes visible within an hour or two. For some hours it fades under thumb pressure and shifts if the body is turned, but after roughly 8 to 12 hours it becomes fixed, as the pooled blood breaks down and stains the tissue around the vessels. Its timing varies too much to date a death on its own, so pathologists weigh it with body cooling, rigor mortis and other evidence.

Its main value lies elsewhere. Fixed lividity on surfaces that were not lowest when the body was found shows that the body was moved, and an unusual color can hint at the cause: cherry red after carbon monoxide poisoning, pink after death from cold. It must also be told apart from a bruise, in which blood has escaped from torn vessels.