Once death occurs in a body, it undergoes a series of changes that occur in a timely and orderly manner. These stages are also affected by the extrinsic and intrinsic factors of the corpse. There are 4 stages: Pallor Mortis, Algor Mortis, Rigor Mortis and Livor Mortis.
Death is one of the most fundamental facts of life. It occurs in all organisms and is inevitable. There are 4 stages or changes that occur in the body after death. These are used as indicators to determine the cause, time, etc., especially in forensic pathology. We’ve often heard some of these terms used in movies, such as lividity, rigor mortis, etc. Most of us must also be familiar with these signs, even though we might not know the technical terms for them.
Stages of Death
Once death occurs in a body, it undergoes a series of changes that occur in a timely and orderly manner. These stages are also affected by the extrinsic and intrinsic factors of the corpse. Determining the stage and state of decomposition of the body, the pathologist can estimate a time frame in which death occurred, which is essential in medicolegal investigations. Since there is no fixed duration for these stages, it is impossible to determine the exact time of death unless there is a witness or another verifiable source of this information.
The time difference between the time of death and the examination of the body is known as the Post Mortem Interval (PMI). The longer the PMI, the larger the time of death window will become, i.e., harder to determine the time of death. There are 4 stages: Pallor Mortis, Algor Mortis, Rigor Mortis and Livor Mortis.
The first change that occurs in a corpse is the paleness in the face and other parts. This is due to the cessation of the capillary circulation. This is the very first sign and occurs very rapidly, within 15-30 minutes of death. Due to this, it is usually insignificant in terms of determining the time of death, unless of course, death has occurred shortly before the finding of the body. Studies have also proven that the paleness is unaffected by gender differences in bodies.
Humans are warm-blooded organisms, i.e., we can control and maintain our inside temperature, regardless of the outside environment. This property, however, ceases to function after death. Hence, a corpse will eventually start cooling or heating to match the outside temperature. Our bodies are usually warmer than the outside temperature, and thus the bodies cool. However, if the body is in a warmer environment, it would heat up.
The rate at which the temperature of the body is acclimatizing to the outside environment gives some indication of the PMI. However, it can be affected by a number of factors, such as fluctuations in outside temperature, the thickness of clothing on the corpse, the place where the corpse has been found, any drugs or other intrinsic factors that could affect this temperature adjustment, etc. Therefore, it cannot be used alone to determine the time of death.
After death, a corpse will first go flaccid, i.e., all the muscles will become weak. After this, the whole body will stiffen, i.e., the muscles will contract and stay in that position. This stiffening of the body is known as rigor mortis. It helps in a number of ways and can be used as a tool in determining the time of death. Based on the position of the body in rigor, certain other deductions can be made, such as whether the site where the body was found is the site of death, if the person died in a particular position etc. Expressions also freeze on the face of a victim, which helps in giving further insight into the nature of their death.
What causes Rigor Mortis?
Muscles need energy to function. This is provided in the form of ATP (adenosine triphosphate) molecules. Our muscles are composed of 2 bands called myosin and actin. These 2 bands move together towards each other and form bonds. This is how our muscles contract. Energy is then required to break these bonds and let the bands move away from each other, thereby relaxing the muscle. After death, respiration stops, so no more ATP is produced. Therefore the muscles freeze in the position they are in. Although it starts affecting the whole body at the same time, the smaller muscles like those of the eyelids, face, etc. stiffen first due to their small size.
How long does rigor mortis last?
The process of rigor mortis starts within 2 hours of the occurrence of death and is usually completed by around 8 hours. Although there is no fixed time as to how long the body would stay in that position, studies suggest a range from 18 hours to 2 days. This is also affected by the ambient temperature, the rate of decomposition of the body etc. Rigor mortis ends due to the decomposition of the muscles and body. Hence it is highly dependent on the outside and inside environment.
This is the final stage of death. When the heart stops beating, the blood is now at the mercy of gravity. It tends to collect at the dependent part of the body. Depending on the position of the body, these parts would vary. For instance, if the person was flat on their back when they died, the blood would collect in the parts that are touching the base. If the person was hanging, it would collect in their fingertips, toes, and earlobes. This blood gives the skin a bluish appearance.
Initially, when the skin is pressed, the skin would turn white and return to the bluish color upon the removal of the pressure. After approximately 12 hours, however, the blood gets “fixed” there and the skin wouldn’t turn white. The bluish coloring of the skin is called livor mortis or lividity.
Lividity can give insight into the time of death. It can also help investigators determine if the body has been moved from another place.
All these stages of death are often overlapping in their occurrence. They may start separately, but most of them continue to occur simultaneously. However, other factors are also taken into consideration during investigations. This is mainly because there are factors that can affect these stages considerable. Hence, investigators never rely only on one or 2 factors, but rather take a number of them into consideration and then draw their conclusions.
- National Center for Biotechnology Information (NCBI) (Link 1)
- National Center for Biotechnology Information (NCBI) (Link 2)
- National Center for Biotechnology Information (NCBI) (Link 3)
- National Center for Biotechnology Information (NCBI) (Link 4)
- Indiana University – Purdue University Indianapolis