Rigor Mortis, Livor Mortis, and Algor Mortis: How Time of Death Is Estimated

After the heart stops, the body changes in a steady, predictable way. Three of those changes happen early, and they have Latin names: rigor mortis, livor mortis, and algor mortis. Doctors and investigators use them to estimate how long ago someone died. This article explains what each one is and how reliable the estimates are.

What are the three early changes after death?

They are cooling, color change, and stiffening. NIH’s StatPearls library calls them the classical triad of early postmortem changes, and they happen while the body is still in what experts call the fresh stage, before soft tissues break down.

• Algor mortis is the cooling of the body until it matches the temperature of its surroundings.
• Livor mortis is a purple-red discoloration caused by blood settling.
• Rigor mortis is the stiffening of the muscles.

What is rigor mortis?

Rigor mortis is the stiffening of muscles after death. It starts in the small muscles of the face about 2 hours after death. Over the next few hours it spreads to the arms and then the large leg muscles, and it is complete by about 6 to 8 hours. The stiffness stays for roughly another 12 hours, up to about 24 hours after death. Then the proteins that locked the muscles together begin to break down, and the stiffness fades. By about 36 hours it has generally disappeared, and the muscles become soft again.

Rigor mortis is not the same as cadaveric spasm. That is an instant clenching of a small group of muscles at the moment of death. It is rare and is seen in some violent deaths, such as drowning.

What is livor mortis?

Livor mortis (also called lividity) is caused by gravity. When the heart stops, blood no longer moves around the body. It slowly pools in the lowest parts, which can turn the skin there reddish-purple. Reference sources commonly report that the color is visible about 2 hours after death and becomes fixed after roughly 8 to 12 hours. Early on, pressing the skin makes the mark turn pale (called blanching). Once it is fixed, it no longer fades. These times depend heavily on conditions such as temperature.

Because blood pools in the lowest areas, the pattern can show how a body was lying. A pattern that does not match the body’s position can suggest that it was moved after the color became fixed.

What is algor mortis?

Algor mortis is the cooling of the body after death. A living body stays at about the same temperature, and after death it cools until it reaches the temperature of the room or place around it. StatPearls describes algor mortis as the most accurate single method for estimating time of death in the early hours. But the speed of cooling depends on the person’s size, their clothing, and the air around them, so it is never used alone.

How accurate is an estimate of time of death?

Not very exact. A chapter reviewed by the National Institute of Justice says it is usually not possible to fix time of death from a single change. Investigators get better hints by studying several changes together with the body’s internal temperature. StatPearls adds that a careful forensic pathologist will not estimate time since death from cooling alone. TV shows often give an exact hour. Real experts give a range.

What happens after these early changes?

The body continues to break down. StatPearls lists five stages of decomposition: fresh, bloated, active decay, advanced decay, and skeletal. These stages can overlap, and temperature and surroundings change how fast they happen. For a broader look, see What Happens to Your Body After You Die and What Happens to Your Body in the First 24 Hours.

Why do these changes matter outside of crime stories?

They help medical examiners and coroners work out when a death happened and whether a body was moved. This matters in unexpected or unwitnessed deaths. In most deaths, such as a death in hospice with family present, nobody needs to estimate anything, because the time of death is simply recorded. If you want to know how a death is confirmed, read How Does a Doctor Know Someone Is Dead?, and for how investigations work, see Coroner vs. Medical Examiner.