Lividity, also known as livor mortis, is a reddish-purple discoloration of the skin that appears after death. It is one of the earliest signs observed in a deceased individual, offering preliminary indications about the post-mortem period.
The Science of Lividity
Lividity arises from a passive process where blood settles due to gravity after the heart stops. Red blood cells, heavier than plasma, sink within capillaries in the dependent, or lowest, parts of the body. This pooling results in the characteristic purplish-red discoloration. Areas where pressure is applied, such as where the body rests against a surface, typically remain pale.
Lividity can begin to appear as faint red patches within 30 minutes to 2 hours after death, though it is usually not easily observable until about two hours post-mortem. These patches increase in intensity and spread over the dependent regions, becoming well-formed within 3 to 4 hours. Lividity reaches its maximum visibility and becomes “fixed” approximately 8 to 12 hours after death, meaning the pooled blood no longer shifts if the body’s position is changed.
The color of lividity can vary. A cherry-red or bright pink coloration can indicate carbon monoxide or cyanide poisoning. Conversely, severe anemia or significant blood loss prior to death can result in very faint or absent lividity.
Lividity’s Role in Investigations
The presence, extent, and fixation of lividity provide important information in forensic investigations. Observing the stage of lividity helps estimate the time elapsed since death. If lividity is present but still blanches when pressed, it suggests death occurred recently, within the first few hours. If fixed and not blanching, it indicates a longer post-mortem interval, typically beyond 8-12 hours.
Lividity patterns are important for determining the body’s position after death and whether it has been moved. If a body is found lying face down, but lividity is fixed on the back, it indicates the body was originally lying on its back for a period of time before being moved. This inconsistency suggests post-mortem relocation. Forensic examiners often press on discolored areas to assess fixation, providing a visual clue regarding body movement.
Lividity Versus Other Marks
Lividity must be distinguished from other marks that might appear on a deceased body, particularly bruising. It is a passive process where blood settles within intact blood vessels due to gravity, resulting in uniform discoloration across dependent areas without tissue injury. In its early stages, lividity can be blanched, meaning the color temporarily disappears when pressure is applied.
In contrast, a bruise results from trauma where blood vessels rupture, allowing blood to escape into surrounding tissues. Bruises show signs of tissue damage and do not blanch under pressure. Lividity also differs from marbling, a decompositional change involving greenish-black streaks in blood vessels due to bacterial activity, typically appearing 24 to 48 hours after death.