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Describe postmortem lividity with its colours and medicolegal importance.

Forensic Medicine · 2nd Professional — Para-Clinical

Definition and Development

Postmortem lividity (livor mortis, hypostasis, postmortem staining, suggillation) is the bluish-purple discolouration of the dependent parts of the body produced by the gravitational settling of blood within the vessels after the circulation has ceased.

Mechanism — once the heart stops, the blood is no longer circulated and sinks under gravity into the dependent capillaries and venules. It remains intravascular, which is the fact that distinguishes it from a bruise
Timing — begins as small patches within 30 minutes to 2 hours (internally it begins almost at once); becomes confluent and well developed by 4 hours; reaches maximum intensity at about 6 to 8 hours; and becomes fixed between 6 and 12 hours
Fixation — before fixation, turning the body causes the lividity to shift completely to the new dependent area; between about 6 and 12 hours it shifts only partially, so patches appear at both sites; and after fixation it does not shift at all. Fixation occurs because the blood haemolyses and the pigment diffuses into the surrounding tissues, and because the vessels are compressed and thrombosed
Contact pallor (contact flattening) — lividity is absent where the skin is compressed against a firm surface or by tight clothing, because the capillaries there cannot fill. This produces pale areas over the shoulder blades, buttocks and heels in a body lying supine, and pale bands at the waistband, collar, brassiere and shoe straps. The pattern of these pale areas reproduces the surface on which the body lay, and may show that a garment has since been removed

CLINICAL PEARL

Lividity tells you the position the body has been in for the last six hours, not the position it died in. If lividity is fixed on the back but the body is found face down, it has been moved after death — and moved late enough for fixation to have occurred first. This single observation has established that bodies were transported, that hangings were staged and that scenes were altered, and it is available to any doctor who turns the body over and looks.

Colour of Lividity

Colour	Cause
Bluish-purple / dark blue	The normal colour, from deoxygenated haemoglobin
Cherry-pink / cherry-red	Carbon monoxide poisoning — carboxyhaemoglobin. The classical and most important abnormal colour
Pink (bright)	Death from cold or hypothermia, and in bodies refrigerated or kept in a cold place — because oxyhaemoglobin does not dissociate; also cyanide poisoning
Chocolate-brown	Methaemoglobin — poisoning by nitrites, nitrates, potassium chlorate, aniline dyes, nitrobenzene and phenacetin
Deep blue / bluish-black	Asphyxia, and opioid poisoning
Bronze / reddish-bronze	Clostridium welchii septicaemia, classically after criminal abortion
Greenish-brown	Hydrogen sulphide poisoning; and putrefaction
Pale or feeble lividity	Severe haemorrhage and anaemia — there is too little blood to produce it, which is itself a useful finding

Distinction from Bruising, and Medicolegal Importance

Feature	Postmortem lividity	Bruise (contusion)
Site	Dependent parts only, and sparing pressure areas	Anywhere — wherever the injury was inflicted
Margins	Diffuse, merging gradually	Well defined
Elevation and swelling	Absent	Usually present
Colour change with time	Does not pass through the colour changes of a bruise	Passes through red, blue, purple, green, yellow and brown as haemoglobin is broken down
On incision — the decisive test	Blood is intravascular; it exudes from cut vessels and the tissue washes clean under a stream of water, leaving normal tissue beneath	Blood is extravascular, infiltrating and clotted in the tissues; it does not wash away, and the tissue beneath is stained and often torn
Histology	Blood within vessels; NO vital reaction	Extravasated blood with a vital reaction — inflammatory infiltrate, and later haemosiderin
Effect of pressure before fixation	Blanches on pressure and shifts on turning the body	Does not blanch or shift

Medicolegal importance of lividity — it is a sure sign OF death; it gives a rough estimate of the time since death from its development and fixation; the colour may indicate the cause of death, particularly carbon monoxide; it shows the position of the body after death and whether it has been moved; the pattern of contact pallor indicates the surface on which it lay and may show that clothing or a ligature has been removed; and it must not be confused with bruising

Applied Aspects

Incise every suspected bruise; this single test settles the question in seconds, and mistaking lividity for a bruise is among the commonest and most damaging errors in medicolegal autopsy
Turn the body and look at the back before doing anything else; lividity inconsistent with the position in which the body was found indicates that it was moved after death
Note cherry-pink lividity and think of carbon monoxide; it may be the first indication in a fire death, a suicide by vehicle exhaust, or a faulty heater, and it directs the toxicology
Do not mistake pink lividity in a refrigerated body for carbon monoxide; cold produces the same appearance, and the interval and storage conditions must be considered
Record the pattern of contact pallor; pale bands where no clothing is now present indicate that a garment, belt or ligature was in place after death and has since been removed
Lividity may be scanty or absent in severe haemorrhage, and its absence in a body that should show it is itself a finding worth reporting

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