Timeline of Rigor Mortis
There are many factors to consider when examining rigor mortis in order to come to any conclusions or findings about a person's death. This is the general timeline that rigor mortis will follow under regular conditions:
0 to 8 Hours: The body starts to stiffen, but is still movable
8 to 12 Hours: Muscles become completely stiff
12 to 24 Hours: Muscles stay stiff
24 to 36 Hours: Stiffness dissipates and muscles become flexible
Timeline Factors
In the earlier timeline, the times listed were a general rule under normal conditions. Many factors can alter the timeline for rigor mortis. The following lists indicate factors that will potentially slow down or speed up the rigor mortis process:
First, here are examples of what accelerates rigor mortis:
- Exercise prior to death
- Hot environmental temperatures
- Convulsions
- Electrocution
- High body temperature and fever
- Drugs that increase body temperature
Now, here are some examples of what decreases the rate of rigor mortis:
- Hypothermia
- Cold environmental temperatures
- Pneumonia
- Hemorrhages
- Nervous diseases
The Stages of Rigor Mortis
According to the Medicolegal Death Investigators Training Manual, there are six stages of rigor mortis in humans. Their stages are:
- Absent
- Minimal
- Moderate
- Advanced
- Complete
- Passed
If you're working as a medicolegal death investigator, these stages would be combined when completing examinations. The four combined stages used in the field are:
- Absent
- Present (a combination of minimal and moderate)
- Complete (a combination of advanced and complete)
- Passed
The absent stage means that rigor mortis has not yet started. The present stage means that rigor mortis has started, but that the muscles can still be moved easily. The complete stage refers to the muscles being at the height of rigor mortis and unable to be moved without force. The passed stage of rigor mortis means that the muscles are in the process of becoming flexible again. After that occurs, the muscles will not re-harden.
Lesson Summary
Rigor mortis is the hardening of body muscles after death because of the body's loss of adenosine triphosphate (or ATP), which is a substance that gives energy to the muscles. Rigor mortis' general timeline moves from initial stiffening of the muscles to them regaining more flexibility again. There are more specific versions of this timeline according to the Medicolegal Death Investigators Training Manual, labeled as Absent, Minimal, Moderate, Advanced, Complete, and Passed.
| Cause |
Timeline |
Stages |
*After death, the body loses its ATP.
*This causes the muscles to harden. |
*0 to 8 Hours: The body starts to stiffen, but is still movable
*8 to 12 Hours: Muscles become completely stiff
*12 to 24 Hours: Muscles stay stiff
*24 to 36 Hours: Stiffness dissipates and muscles become flexible |
*Absent
*Minimal
*Moderate
*Advanced
*Complete
*Passed |
Learning Outcomes
As you delve into this lesson on rigor mortis, you'll increase your capacity to:
- Describe rigor mortis and note its cause
- List factors that can accelerate or decelerate the rate of rigor mortis
- Recite the timeline and stage for rigor mortis
