lividity

Lividity, also known as livor mortis or postmortem lividity, is the gravitational settling of blood in the tissues after death. With circulation absent, red blood cells settle in the dependent parts of the body, producing a reddish-purple discoloration of the skin and underlying tissues. The color reflects the hemoglobin in blood that becomes deoxygenated as it pools in those regions.

Onset and progression occur as the body remains in a given position. Lividity typically begins within 20 minutes to a few hours after death, becomes conspicuous within several hours, and becomes fixed (no further movement with position) after roughly 6 to 12 hours, depending on temperature and other conditions. Warmer environments tend to accelerate onset and fixation, while cold conditions slow the process.

Distribution follows body position at death. In a person lying on the back, dependent areas such as the back and posterior aspects show lividity; in a person lying prone, the front surfaces exhibit it. Because lividity shifts with movement before fixation, investigators assess whether the body was moved after death by noting any inconsistencies between expected patterns and observed staining.

Forensic significance includes estimating time since death and clues about body position and movement after death. Lividity is distinguished from other skin discolorations and from living conditions such as livedo or vascular disorders. Cadaveric lividity is a standard postmortem finding used alongside other signs in death investigation.