What is Algor Mortis? | Stages of Death

Lesa Steen, Elisha Madison
  • Author
    Lesa Steen
  • Instructor
    Elisha Madison

    Elisha has Master's degree in Ancient Celtic History & Mythology, as well as a Bachelor's in Marketing. She has extensive experience creating & teaching curricula in college level education, history, English, business and marketing.

What is algor mortis? This lesson defines algor mortis and also describes the other stages of death, livor mortis and rigor mortis. Updated: 08/31/2021

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What is Algor Mortis?

Algor mortis is the second stage of early and noticeable changes that occur during the first 24 to 48 hours after death. Death is the cessation of life which is defined as the irreversible end of blood circulation throughout the body, or the end of brain activity.

The term algor mortis is Latin for "cold death" and refers to the change in the temperature of the body until it matches the ambient temperature. While this usually means cooling, bodies in an environment hotter than normal body temperature will increase in temperature. This change is approximately 1.5 to 2 degrees Celsius for the first hour and drops a rate of around one degree Celsius for each hour after that.

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Stages of Death Mortis

There are key stages of early decomposition that occur during the first 24 to 48 hours of death. The stages of death mortis are:

  • Livor mortis: the first stage of changes after death.
  • Algor mortis: the second stage of changes after death.
  • Rigor mortis: the third stage of changes after death.

Livor Mortis

Livor mortis is defined as the first stage after death. It means "discoloration of death" or "wound of death" in Latin. Liver mortis occurs within 20 to 30 minutes after death and lasts for the first 12 hours. It is the change in body color caused by blood flowing to the lowest points of the body due to gravity pulling it down. This makes the underside darker and the upper side of the body paler. The hemoglobin within the blood turns purple because it is pooling. Liver mortis can aid in helping a criminal investigator determine if the body has been moved from the time that it died due to the pooling affect.

Algor Mortis

Algor mortis is defined as the second stage after death. It starts approximately 30 minutes after death and can continue for the first 48 hours, but typically is complete by 18 to 20 hours after death, unless the body is in an extreme environment. It is caused when the body's thermoregulatory structures and systems stop.

Rigor Mortis

Rigor mortis is the third stage of early decomposition. It roughly translates from Latin as "stiffness of death." This is the stage in which the body stiffens as a result of muscle contractions. Rigor mortis can set in anywhere from one to six hours after death. The average time it takes is usually between two to four hours after death. It can last up to 24 hours before the muscles stop their contractions.

Using Algor Mortis to Determine Time of Death

Algor mortis can be used to help determine the time of death for a person that passes away outside of a medical facility. The time of death is recorded at a medical facility or by a coroner. Using algor mortis to pinpoint time of death can help with criminal investigations by determining when a victim died. We will be discussing the formula used to determine the time of death from algor mortis in upcoming sections. We will also discuss the methods of taking a reading, and factors that influence algor mortis.


Algor mortis is used to determine time of death at crime scenes.

Algor mortis as time of death


Formula to Determine Time of Death

The Glaister equation is used to determine the time of death based on the temperature of the body at the time of discovery or testing.

The formula for the Glaister equation is in Fahrenheit, but it is based on an ambient temperature in degrees Celsius. If the ambient temperature is above 32 degrees C, then the equation is:

{eq}\frac{98.4-T}{1.5^{o}/hour}=Time {/eq}

The T is equal to the temperature measurement of the body. The time is the number of hours the person has been dead.

If the ambient temperature is less than or equal to 32 degrees C, then the equation is:

{eq}\frac{98.4-T}{0.75^{o}/hour}=Time {/eq}

The T is still equal to the temperature of the body in this equation, and the time is the number of hours the person has been dead.

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Frequently Asked Questions

What are the 3 types of mortis?

The three types of mortis are livor mortis, algor mortis, and rigor mortis. They all occur within 48 hours after death.

How does Algor mortis determine time of death?

Algor mortis can determine the time of death because it is based on the equilibrium between the body's temperature and the surroundings. The rate of cooling is known to be either 1.5 degrees per hour if the environment is above 32 degrees C, or 0.75 degrees per hour if it is 32 degrees C or below. The Glaister equation is used to calculate the hours since death.

What happens during Algor mortis?

During Algor Mortis the body's temperature cools to match that of the surroundings. If the body is in a warm environment, the temperature will rise to match the surroundings. It is a result of the body's thermoregulatory system stopping.

What does Algor mortis mean?

In Latin Algor mortis means "cold death." It is the second stage of changes that occur after death as the body's temperature reaches the temperature of its surroundings.

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