Rigor mortis is the stiffening of muscles after death. It begins in involuntary muscles within 1-2 hours, then spreads to voluntary muscles over 6-12 hours. Maximum rigor is reached at 12 hours and passes off over the next 12 hours. It is caused by depletion of ATP and influx of calcium ions into muscles. Rigor mortis can help determine time and position of death, and distinguish ante-mortem from post-mortem injuries. It may be simulated by heat stiffening, cold stiffening, or cadaveric spasm at the moment of death. A case study described rigor mortis revealing an unusual body position, indicating the crime scene differed from where the body was discovered.

1. Presented By:
Ajay Sharma

2. 1. Introduction
2. Primary relaxation or flaccidity
3. Rigor mortis
4. Factors affecting rigor mortis
5. Medico-legal importance of rigor mortis
6. Conditions simulating rigor mortis
7. Secondary relaxation or flaccidity
8. Case study
9. Conclusion
References

4. • Immediate relaxation of muscles after
death.
PRIMARY
RELAXATION
• Latin: rigor "stiffness", mortis "of death”.
• Stiffening of muscles after death.
• Also called as Cadaveric rigidity.
RIGOR
MORTIS
• Rigor mortis disappear.
• Muscles become relaxed and soft.
SECONDARY
RELAXATION
Changes In Muscles After Death

5. • Death is only somatic.
• All the muscles are begin to relax soon after death.
• Joints become flexible and all muscles lose their tension.
• Contact flattening of body.
• Muscles may respond to mechanical, electrical or chemical stimuli.
• Pupils react to atropine or physostigmine, but not to light.
• Peristalsis may occur in intestine with cilia movement of intestinal cells.
• After death, as long ATP presents, muscles are relaxed.
• ATP is produced by anaerobic glycolysis.
• This stage lasts from 3─6 hours, but the average is 2─3 hours.

6. STRUCTURE OF SKELTAL MUSCLE

7. Fig. 1: Stages in Actin and Myosin cross cross bridge formation and breaking

8. • Appearance of rigor mortis indicates
death of individual cells.
• After death the ATP is progressively
and irreversibly destroyed.
• There is no resynthesis of ATP.
• Calcium ions to flood the contractile
units of the muscle fibres
(sarcomeres) because of membrane
disruption and lack of ATP.
• Increased calcium level in the
sarcomeres causes muscle
contraction.

9. Fig.2: Binding of actin and
myosin filaments
Fig.3: Diagrammatic representation of
muscle contraction

10. • Rigor mortis first appears in the involuntary muscles, and then in the
voluntary muscles (Nysten’s rule).
• In the heart it appears, within an hour after death and may stay for
10–12 hours.
• In the voluntary muscles rigor mortis follows a definite course.
• The disappearance of rigor follows the same fashion as its
appearance.
 According to Shapiro─ Rigor mortis most likely to develop
simultaneously in all the muscles.

11. Fig.4: Showing order of appearance and disappearance of Rigor

12. ●Human skeletal (voluntary) muscle contains two types
of fibres
Type I (red)
●Aerobic slow twitch muscle
●Rigor develops early
Type II (white)
●Anaerobic fast twitch muscle
●Rigor develops late
•Development of rigor is concerned with muscles only.
•If force is applied when rigor is fully developed, stiffness is broken
up permanently and the rigid muscles may show postmortem
ruptures.

13. • It may affect the eyes unequally, making the pupils unequal.
• Contracted, stiff, left ventricle may be mistaken for left ventricular
hypertrophy.
• Rigor in the muscle of scrotum, may be responsible for postmortem
expulsion of semen.
• It causes goose-skin or pimpling appearance of the skin with the
erection of cutaneous hairs (cutis anserina) .
• It may cause expulsion of the foetus.
• Muscle relaxation immediately after death with opening of the eyes
and mouth and subsequent fixation in rigor mortis, changes face
expression.

14. • Rigor is tested by trying to lift the
eyelids.
• Depressing the jaw.
• Gently bending the neck.
• Try flexing/extending various
joints of the body.
Note the degree (absent,
minimal, moderate, advanced or
complete) and distribution
(patchy/complete).

15. Apparent
in 1-2
hours after
death
Well
established
in 9-12
hours
Maintained
for 12
hours
Pass off in
same
manner
Generalized categorization of Appearance and Disappearance of
Rigor Mortis

16. It is generally considered that it takes about 12 hours after
death to develop rigor mortis, remains for another 12 hours and takes
about 12 hours to pass-off. This is also called as March of rigor.
Fig. March of Rigor

17. Age
Nature of
Death
Condition of
Muscles before
Death
Atmospheric
conditions
Influence of
CNS
•Adult, Child or Old
•Natural, Disease or
Poisoning
•Healthy, Robust, at Rest
or Weak and Exhausted
•Cold or Hot
•No effect of brain

18.  It is the sign of death.
 It helps in estimating time since death to some extent.
 It indicates the position of the body at the time of death to some
extent.
 It helps in determining whether a still-born child is alive in uterus up
to the initiation of birth process and died during the process of
delivery.
 It is also developed in paralyzed limb.
 It shows whether body is disturbed from its original position or not.

19. 1) Heat Stiffening
• It is seen in deaths from burning, high voltage electric shock and from
falling into hot liquid.
• Heat causes stiffening of the muscles, because the tissue proteins are
denatured and coagulated as in cooking.
• Muscles are contracted, desiccated or even carbonized on the surface.
• The body assumes an attitude commonly called ‘pugilistic attitude’
(Boxer’s attitude) with lower limbs and arm flexed and hands clinched.
(Fig.5)
• This heat stiffening cannot be broken down by extending the limbs as in
rigor mortis.
• Stiffening remains until the muscles and ligaments get soften due to
decomposition.
• In such state, rigor mortis do not occur.

20. Fig.5: Heat stiffening of body showing
pugilistic attitude

21. 2. Cold Stiffening
• When a body is exposed to freezing
temperatures, the tissues become frozen
and stiff.
• Freezing of the body fluids and
solidification of subcutaneous fat
simulating rigor.
• When the joints are forcibly flexed, ice
breaks in the synovial fluid with a sudden
sharp sound.
• If the body is placed in warm atmosphere,
the stiffness disappears and after a time,
the normal rigor mortis occurs rapidly and
passes off quickly.
• Hardening of the subcutaneous fat,
particularly in infants, may render the
skin-folds rigid and may be mistaken for
ligature marks.

22. 3. Cadaveric Spasm or Instantaneous Rigor
• Cadaveric spasm is a well-recognized but quite rare phenomenon.
• Primary flaccidity does not occur in case of cadaveric spasm, and
the muscles undergo stiffening at the moment of death.
• This is usually limited to a group of voluntary muscles.
• Adrenocortical exhaustion, which interferes with the resynthesis of
ATP, may be the possible cause of cadaveric spasm.
• It is usually associated with the violent deaths occurring under
circumstances of intense emotions.
• No other condition simulates cadaveric spasm and it cannot be
produced by any method after death.
• It passes without interruption into normal rigor mortis .

23. The obvious circumstances of
cadaveric spasm may be:
• It may be encountered in cases
of drowning (fig.6).
• Death from violent disturbance of
nervous system .
• Strychnine, cyanide poisoning.
• In suicidal deaths (fig.7).
• In certain cases of homicides.
• In certain cases of accidents
such as mountain fatalities.
Fig.7: Victim of suicide
Fig.6: In case of drowning.

24.  Presence of cadaveric spasm indicates that person was alive at
the time of instantaneous rigor.
 It indicates ante-mortem nature of drowning.
 In case of suicide, when some weapon is found clenched tightly in
the hand of the deceased is a strong presumptive evidence of
suicide.
 If the deceased dies due to assault, some part of clothing of his
assailant or some hair may be firmly grasped in the hands.
 Cadaveric spasm helps in indicating the mode of death i.e.,
whether suicide or homicide or accidental.

25. Differences Between Rigor Mortis And
Cadaveric Spasm
FEATURES RIGOR MORTIS CADAVERIC SPASM
Time of onset 1-2 hours after death Immediate
Mechanism Due to depletion of ATP Not clearly known
Muscles involved All muscles (both voluntary and
involuntary) are involved
gradually.
Usually restricted to single
group of voluntary muscles.
Muscle stiffening Comparatively moderate Comparatively strong
Predisposing
factor
None Sudden death, excitement,
fear, emotional disturbance,
etc.
Molecular death Occurs Does not occur
Electrical stimuli Muscles do not respond Muscles respond
Medico-legal
importance
Helps to know time since death,
position of body
Indicates mode of death
(whether suicide/ homicide/
accidental)

26. • This sort of stiffening occurs in dead bodies
showing signs of decomposition.
• Gases evolving during putrefactive processes also
stiffen the body, due to accumulation of gases in
tissues.
• Usually, this poses no problem in distinguishing
from true rigor.
4. Gas stiffening

27. • Rigor mortis disappears, and the muscles become soft and flaccid.
• Muscles do not respond to a mechanical or electrical stimulus.
• This is due to myosin being dissolved by the excessive production of
acid during the stage of rigor mortis.
• It may caused by the action of the alkaline liquids produced by
putrefaction.
• Enzymes are developed in dead muscle which dissolve myosin by a
process of auto-digestion.
• The signs of decomposition start appearing on the body.
• The body becomes totally relaxed and flaccid and can be put in any
position or posture.

28. • July, 2011. Dead body of an unknown female aged about 25 years was
brought for medico legal autopsy with an unknown history, but with the
suspicion of a murder.
• Autopsy was carried out after 3 h from the time of finding the dead body
in an isolated place at the suburbs of Bangalore, India.
• The body was found in an unusual position at about 7 am, when the
temperatures at that place ranged between 21°C─27°C in the past 6 hrs.
• During autopsy, the dead body was found with well established rigor
mortis all over the body.
• A horizontal ligature mark was seen completely encircling the neck.
• Autopsy findings were consistent with a death due to ligature
strangulation.

29. Photograph from Right side of body
Photograph from Left side of body

30. • The autopsy confirms that there was no decomposition, and the stiffness
seen in the unusual position, is due to rigor mortis.
• The victim's dead body was disposed off, after positioning in an unusual
way, prior to the onset of the rigor mortis.
• Such an unusual positioning of the dead body is not possible at the flat
surface, where the dead body was found disposed off.
• It shows that the dead body has originated from a different place.
• Many factors affect the onset or progress of rigor mortis, after considering
the usual possibilities, the dead body must have reached the place of
disposal, from 2 to 6 hours after the death.
• To conclude, the clues from the ‘rigor mortis in an unusual position’ are
revealing a homicidal offence and an attempt to hide the evidence. The
investigations in this case had not proceeded further because the victim
was unidentified.

31. • Following death, muscles of the body pass through three phases, i.e.
primary flaccidity, rigor mortis and secondary flaccidity .
• The importance of these changes is related primarily to their
sequential nature that can be utilized to estimate the time since death.
• Estimation of postmortem interval may be extremely helpful in the
screening procedure in some cases.
• Rigor mortis helps in determining position and conditions of body at
the time of death and manner of death.
• It may be confused with cadaveric spasm, heat stiffening and cold
stiffening.

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https://en.wikipedia.org/wiki/Rigor_mortis (visited on 5/2/19)