Determining the Time of Death through Postmortem Changes: Algor, Rigor, and Livor Mortis

BY Amberdawn Jaslene Andres | August 12, 2020

Determining the Time of Death through Postmortem Changes: Algor, Rigor, and Livor Mortis

The time of death is one of the most important details to be gathered by a medical examiner or forensic experts, as this could be the lead and a starting point for further investigations. Also, the time of death could be helpful information for reconstructing the events that might have happened before and during the incident. Moreover, determining how long the body has been dead could lead to exposing the assailant.

There are lots of changes that a body will experience after death. The main changes that can be observed are the Algor, Rigor, and Livor Mortis. These three are crucial in estimating the time of death. However, all of these need to consider a lot of factors during the estimation.

Algor Mortis

The term Algor came from a Latin word “cold”, and Mortem means “death”. A body will decrease in temperature from a normal temperature after death. The difference between the rate of the normal and the post-mortem temperature could estimate how long the body has been dead. 

However, there are several factors that may affect the rate of decreasing in body’s heat. Some factors include the thickness of the clothing, weather, location, illness, and the physique. If the deceased wore a thick clothing before he or she died, that could decelerate the rate of decreasing in the body’s temperature. The weather could also be a factor if the incident happened during winter, which will accelerate the algor mortis. A body that was set into enclosed environment will cool down slower than a body that is exposed freely. Chronic illnesses, dehydration, and sickness associated with fever will raise the temperature after death. In addition, a fat person will take time to cool down than a thin person. 

In order to estimate the time of death using algor mortis, regardless of the factors that could speed up or to slow it down, there is a general rule for normal circumstances. A dead body decreases its temperature at a rate of 1-1.5 ℉ every hour. For example, the normal temperature of a body is 99 ℉ and it drops to 90 ℉ after death. That means, the person died between 6- 9 hours ago. 

Keep in mind that an algor mortis approximately last up to two days only, and will pass after it reaches the ambient temperature.

Rigor Mortis

The word Rigor came from a Latin word “stiff”. A body becomes stiff after death due to chemical activities in the body. Muscles need oxygen. When a person stops breathing, there is no oxygen supplying the muscles anymore causing it to no longer perform an aerobic respiration. The Aerobic Respiration is a process of transferring energy into cell through chemical reactions. With that, the body stiffens and contracts.

Like Algor Mortis, there are also factors affecting the Rigor Mortis. A clothed body will have faster rigor, as well as thin individuals as they have lower fats in the body and no extra oxygen is stored in body unlike those who have larger quantity of it. A person who have done exercise before she or he died will also have faster Rigor. Besides, the cooler temperature of the location, the slower the Rigor Mortis to set.

Small muscles in the eyelids, mouth, jaw, fingers, toes and neck will experience the stiffening of the muscles within 2-3 hours after death. Next, it will go down to the upper limbs after 4-6 hours, then to lower limbs after 8-10 hours. With this estimation, based on what part of the body is already in Rigor Mortis, we could understand how long the body might have been dead.  This will last for almost 36 hours after death. This will disappear after and the body will be relaxed again.

Livor Mortis

Livor mortis, also known as Post-Mortem Lividity, is the pooling of the blood due to the gravity causing discoloration of body after death. Blood contains red blood cells. When the heart stops working, the distribution of red blood cells in the entire body will stop. It will start to depend on the gravity. So whatever part of the body that is dependent, this is where the blood will settle. However, there is a case called “contact pallor” or “contact flattening” in which a body that is pressed on the surface or tied in compression will not experience discoloration due to obstruction of vessels. Lividity, on the other hand, does not depend only on gravity, but also the position of body.

During the first 2 hours, there is an early indication of lividity. In 2-5 hours after death, this is when a Livor Mortis is quite clear and noticeable. At the first 6 hours, lividity can be altered if moved. But after 6 hours of death, even if the body is moved or not, the lividity is fixed. This is because, the blood will start to coagulate in the dependent or bottom parts of the body. A fixed lividity does not disappear. It will stained in the body.


Remember that the usage of post-mortem changes does not give an accurate time of death. It will only estimate the range of time in which the body could have died. Also, the estimation in time of death should be done by an expert in forensics or in medical as it could be quite critical, and has many factors to consider. Still, this could be a basic knowledge for those who want to enter the field of forensics. 


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