What is the Difference Between Rigor Mortis and Livor Mortis

Post-mortem changes refer to the series of changes that occur to the body after death. These changes can be early post-mortem changes and late post-mortem changes. The stages that follow shortly after the death may include corneal opacity, Pallor mortis, Algor mortis, Rigor mortis, Livor mortis, and putrefaction. This article examines the difference between rigor mortis and livor mortis.

The key difference between rigor mortis and livor mortis is their impact. Rigor mortis is the stiffening of the limbs after death, while livor mortis is the accumulation of blood in the lower part of the body after death.

CONTENTS

1. Overview and Key Difference
2. What is Rigor Mortis 
3. What is Livor Mortis
4. Similarities – Rigor Mortis and Livor Mortis
5. Rigor Mortis vs Livor Mortis in Tabular Form
6. Summary – Rigor Mortis and Livor Mortis
7. FAQ – Rigor Mortis vs Livor Mortis

What is Rigor Mortis?

Rigor mortis is also known as postmortem rigidity. It is the fourth stage of death. Rigor mortis is also one of the most recognizable signs of death. Rigor mortis is characterized by the stiffening of the limbs of the corpse. It is caused by chemical changes, such as calcium in the muscles.

Rigor mortis occurs after four hours of death. Moreover, Rigor mortis is not permanent. It usually begins to pass hours after the onset. At room temperature, it lasts 8 hours. Furthermore, rigor mortis also has applications in industries such as the meat industry and forensic pathology. The onset of rigor mortis affects meat tenderness in the meat industry, while the degree of rigor mortis helps determine the approximate time of death in forensic pathology.

What is Livor Mortis?

Livor mortis, also known as the postmortem lividity or hypostasis, is the second stage of death. In Livor mortis, the blood settles in the lower parts of the body postmortem. This causes a purplish-red discolouration of the skin of the body.

Livor mortis occurs within 20 to 30 minutes after death and is caused by the cessation of heart activity. As a result, blood stops circulating and settles, causing the heavier red blood cells to sink through the serum due to gravity. This process leads to the pooling of blood in the lower parts of the body. Livor mortis is usually not recognizable by human eyes till two hours after death. Moreover, the maximum lividity occurs after 8 hours and 12 hours. Furthermore, Livor mortis is used in forensic entomology along with Algor mortis, Rigor mortis, and other practices.

Similarities Between Rigor Mortis and Livor Mortis

1. Rigor mortis and Livor mortis are two different types of stages of postmortem changes in the body.
2. They are signs of death that are recognizable.
3. Both are applied in the forensic pathology.

Difference Between Rigor Mortis and Livor Mortis

Definition

1. Rigor mortis is the stiffening of the limbs after the death.
2. Livor mortis is the accumulation of blood in the lower part of the body after death.

Stage

1. Rigor mortis is the fourth stage of death.
2. Livor mortis is the second stage of death.

Occurs after

1. Rigor mortis occurs four hours after death.
2. Livor mortis occurs 20 to 30 minutes after death.

Clinical Features

1. Rigor mortis is characterized by rigidity in the lower limbs.
2. Livor mortis is characterized by purplish-red discoloration of the skin of the body.

Ends or Reaches the Maximum After

1. Rigor mortis ends after 8 hours.
2. Livor mortis reaches its maximum after 8 to 12 hours.

Application

1. Rigor mortis is used in the meat industry and forensic pathology.
2. Livor mortis is used in forensic entomology.

The following table summarizes the difference between Rigor mortis and Livor mortis.

Summary – Rigor Mortis vs Livor Mortis

Post-mortem changes are the clinical signs and stages of the death. Rigor mortis and Livor mortis are two different types of stages of postmortem changes in the body. Both are signs of death. However, Rigor mortis is the stiffening of limbs after death, while Livor mortis is the accumulation of blood in the lower part of the body after death. This is the summary of the difference between Rigor mortis and Livor mortis.

FAQ: Rigor Mortis and Livor Mortis

1. Why do bodies stiffen after death?

• Rigor mortis is the post-mortem stiffening or rigidity of the lower parts of the body. This is due to a decrease in levels of adenosinetriphosphate (ATP) beyond critical levels. It leads to calcium ions flooding muscle fibres due to the loss of integrity of the muscle cells.

2. How long does it take Rigor mortis to begin?

• Rigor mortis appears approximately 2 hours after death in the muscles of the face and progresses to limbs over the next few hours. It appears in the lower limbs after 4 hours of the death. Rigor mortis is completed between 6 to 8 hours after death.

3. What are the four mortis?

• Pallor mortis (where the skin pales due to blood pooling), Algor mortis (where the body cools over time), Rigor mortis (where muscles stiffen and contract) and Livor mortis (where areas of pooled blood begin to take on a bruised-like discoloration) are the four mortis.

4. What is the livor mortis stage of death?

• Postmortem lividity or Livor mortis is the settling of blood in the lowest part of the body due to the action of gravity. In this stage, the blood will start pressing on the skin, leaving red/purple marks on the body.

5. What causes Livor mortis?

• Livor mortis is caused by the stopping of the heart. It is caused by the cessation of heart activity. As a result, blood stops circulating and settles, causing the heavier red blood cells to sink through the serum due to gravity. This process leads to the pooling of blood in the lower parts of the body.

Reference:

1. “Rigor Mortis.” ScienceDirect.
2. “Livor Mortis: What Is It, Occurrence, and More.” Osmosis.

Image Courtesy:

1. “Stages of livor mortis” By Frerichs, D., Vidler, A. & Gatzidis, C. – Frerichs, Dhana (2016-07-08). “Biologically inspired simulation of livor mortis” The Visual Computer 33 (11): 1453–1466. Springer Science and Business Media LLC. DOI:10.1007/s00371-016-1291-3. ISSN 0178-2789. (CC BY 4.0) via Commons Wikimedia

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