Rigor mortis is the stiffening of muscles that occurs after death. It begins between 2-6 hours after death as ATP is no longer replenished and calcium causes perpetual muscle contraction. Rigor mortis reaches a maximum at around 12 hours and dissipates around 24-72 hours post-mortem. Several factors can alter its onset and duration including temperature, muscle exertion prior to death, and diseases. It is one sign used to estimate time of death but varies considerably between individuals.

1. RIGOR MORTIS
PRESENTER:
DR.RAJKUMAR. M.G.
PG IN FORENSIC
MEDICINE
SDUMC,KOLAR
DR.KIRAN.J
Prof . &HOD
DEPT. OF FORENSIC
MEDICINE
SDUMC,KOLAR
1
MODERATOR:

2. Rigor mortis (Latin: rigor "stiffness", mortis "of death")
2
Also called as DEATH STIFFENING,CADAVERIC RIGIDITY
RM is one of the recognizable signs of death, caused
by Physiochemical changes in
the muscles(voluntary+involuntary) after death,
causing the limbs of the corpse to become stiff
,shortening of muscle fibres.and difficult to move or
manipulate .
In humans, it commences after about two to six hours,
reaches maximum stiffness after 12 hours, and gradually
dissipates from approximately 24 hours after death.
Depending on temperature and other conditions, rigor
mortis lasts approximately 72 hours.(Rule of 12).

3. MECHANISM/PATHOPHYSIOLOGY:
3
Death
cessation of respiration
depletion of oxygen used in making of ATP
ATP no longer provided to operate the SERCA pumps in
the membrane of the sarcoplasmic reticulum,which pump
calcium ions into the terminal cisternae
calcium ions diffuse from the terminal cisternae and extra
cellular fluid to the sarcomere
Calcium binds with Troponin
Crossbridging between myosin and actin filaments.

4. Unlike normal muscle contractions,the body is
unable to complete cycle and release the coupling
between the myosin and actin,creating a perpetual
state of muscular contraction,until the breakdown
of muscle tissue by digestive enzymes during
decomposition.
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MECHANISM/PATHOPHYSIOLOGY:(contd)

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8. Signal from NERVOUS SYSTEM to contract MUSCLE
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Muscle-->Myofibril-->Sarcomere(contractile unit)

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Myosin-Thick filament/ATP dependent
motor protein.
Actin-Thin filament/Contractile filament
Of muscle cells.

11. Thick filaments- Myosin are anchored to M line(center)
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12. Actin filaments are anchored to outer edge of Sarcomere-Z Line
12

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Myosin pulls Actin filaments along its length:
POWER STROKE

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Sliding filament mechanism:
Lengths of filaments do not change
Sarcomere shortens
Causes shortening of muscle fiber and muscle

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ATP is responsible for elasticity and plasticity of muscle during life.
ATP hydrolysis=ADP+Inorganic phosphate
*Hydrolysis energy=>Power stroke action of Myosin.
 SUPPLY OF ATP IN MUSCLES DURING LIFE:
1. Phosphagen System
2. Glycogen-lactic acid system
3. Aerobic system.

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Muscle contractions are controlled by Calcium ions

17. Regulatory Proteins on Actin :TROPONIN and TROPOMYOSIN
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At RELAXED STATE:
Tropomyosin blocks CROSSBRIDGES,

18. When calcium levels are high enough and ATP is present ,
Calcium binds to Troponin and displaces Tropomyosin and
Helps in formation of Cross bridges.
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19. T-tubule(myofibril)======>>>CALCIUM released.
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Neuromuscular junction
Signal from Nervous system to CONTRACT=>Calcium
Released from sarcoplsamic reticulum.

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Muscle contraction
Z-Lines draw close to M –Lines=shortening of muscle fiber

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Rigor mortis -VIDEO

23. AFTER DEATH:
PHYSIOCHEMICAL CHANGES IN MUSCLE
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ATP is progressively and irreversibly destroyed accumulation
of lactates and phosphates in muscles.
No Resynthesis of ATP
Postmortem SARCOPLASMIC DISRUPTION Flooding of
Calcium Ions into SARCOMERES Initiating the binding of
Actin and Myosin MIMICKING NORMAL CONTRACTION.
Rigor Mortis sets in when ATP is reduced to a critical level(85% of
-normal).Rigidity is MAXIMUM when ATP depletion is 15%.
Rigormortis is lost when putrefaction starts Proteolytic detachment
Loss of Structural Integrity muscles soften and relax.

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ORDER OF APPEARANCE:
Nysten’s Rule:Rigormortis does not start in all muscles
simultaneously.
Shapiro(1950):Rigormortis mostly likely to develop
simultaneously in all muscles.smaller muscles>larger.
Involuntary muscles(myocardium=½hr)>Voluntary muscles>
Eyelids>Neck>Lower Jaw>Face>Chest>Upper Limb>
Abdomen>Lower Limbs>Fingers and Toes.
RM disappears in same order of appearance.

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Rule of 12:

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Development of Rigormortis:
RM is independent of the integrity of nervous system,
concerned only with muscles.
RM occurs in different times with different types of
muscles.(red muscles and white muscles)
Frequent handling of the body breaks rigor in certain
places leaving a patchy distribution.

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Features Observed During Rigormortis:
 Pupils are constricted due to Rigormortis of the muscles
of Iris.
 CUTIS ANSERINA or goose skin appearance due to
Rigormortis of erector pilae muscle.
 Post mortem ejaculations of the seminal fluid in males.
 Rarely,if the uterus is in labour at the time of death,the
RM may cause the uterus to contract and expel the foetus.
 In Heart,contracted stiff Left Ventricle may be mistaken
for LV HYPERTROPHY.

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Time Of Onset:
Time Factor is VARIABLE,beacause of many extrinsic and
intrinsic factors.
When Rigor sets in early,it passes off quickly and vice versa.
In India ,usually it lasts for 24 to 48 hours in WINTER and
18 to 36 hours in SUMMER.It may begin to disappear in
about 12 hrs.
Rule of FIVE:In some states like kerala( moisture),RM sets
in 5hrs - stays for 5hrs –disappears in 5hrs.

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Conditions Altering the Onset and Duration:

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Conditions Altering the Onset and Duration:
Age:
•RM does not occur in a foetus less than 7 months.
•commonly found in stillborn infants at full term,
but it is earlier to appear and also to disappear, so
it has no value as a sign of live birth.
•children & old people:feeble and rapid
Nature Of Death:
1)Diseases causing great exhaustion and wasting(cholera,
typhoid,tuberculosis,cancer, etc) and Violent Deaths(cut
-throat,electrocution,firearms,lightiningStrychnine poisoning)
-»RM EARLY ONSET AND SHORT DURATION.

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Nature Of Death (contd,)
2)POISONING:
• OP poisoning-»rigidity appears early
• CO poisoning-»delays disappearance
• Strychnine and HCN poisoning»»starts early and persists
longer.
3) Asphyxia,severe haemorrhage,apoplexy,pneumonia and
nervous disease causing muscle paralysis -»onset delayed.
4)Widespread bacterial infection, gas gangrene-»
disappear Very rapidly.
*RIGOR MORTIS is frequently absent in septicaemia
deaths.

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Conditions Altering the Onset and
Duration:(contd.)
MUSCULAR STATE:
• Healthy muscles and at rest before Death:slow onset &long
duration of RM.
• Heavy exercise ,Severe Convulsions:Rapid onset and short
duration of RM.
•In a Person who run prior to death,rigor may develop earlier
and rapid in legs,compared to other parts.
•In Emaciated persons:Rigor may be very weak or delayed.

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Conditions Altering the Onset and
Duration:(contd.)
ATMOSPHERIC CONDITIONS:
 Cold Weather--->slow onset and long duration.
 Rigor persists longer in colder wet air ˃fresh dry air.
prolonged by dry cold air and cold water.
 Hot environment:Rapid onset and shorter duration due
to increased breakdown ATP.
 Because of the number variability of the factors which
influence the development of RM,it is not possible to
draw any general rule for rate of onset, duration and
disappearance.

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Conditions SIMULATING Rigor mortis:
1)Heat Stiffening:
Exposure of a Body to intense temperature(>65ºC)
Denaturation&Coagulation of muscular proteins
Muscular shortening(contracted,dessicated,carbonised)
Seen in burning,high voltage electrocution,falling into
hot liquid.
A zone of brownish pink “cooked meat” is seen under
contracted muscle.
Changes in posture,especially flexion of limbs
Normal rigor mortis do not occur.

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Conditions SIMULATING Rigor mortis:(contd)
2)Cold Stiffening:
Exposure of a Body to extreme cold(<-5ºC)
Solidification of subcutaneous fat and muscles,
freezing of synovial fluid in joints.
Rigor mortis is halted until thawing occurs,after which
it develops very rapidly and passes off quickly.
When joints forcibly flexed->sudden sharp sound d/t
ice breakage in synovial fluid.
Subcutaneous fat hardening may be mistaken for
ligature mark,especially in infants.

36. Conditions SIMULATING Rigor mortis:(contd)
3)Cadaveric spasm:
Also known as Instantaneous rigor,cataleptic rigidity or
instantaneous rigidity.
Rare form of muscular rigidity that occurs at the moment of
the death,persists into the period of Rigor mortis and can be
mistaken for RM.
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The cause is unknown,but usually a/w violent deaths
happening with intense emotion(possibly neurogenic),
adrenocortical exhaustion(impairing resynthesis of ATP)
No other condition simulates CS and it cannot be produced
by any method after death.

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3)Cadaveric spasm:(contd,)
May affect all muscles in the body,but typically only groups
such as-forearms/hands
Seen in cases of cases of drowning victims when grass ,weeds
roots or other materials are clutched and provides proof of
life at the time of entry into the water.

38. 3)Cadaveric spasm:(contd,)
Often demonstrates the last activity one did prior to death
and therefore significant in forensic investigations..eg.clinging
on a knife tightly.
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40. RIGOR MORTIS Vs. CADAVERIC SPASM
RIGOR MORTIS
• Muscle stiffening not marked
• Molecular Death occurs
• BODY heat –Cold
• Muscles do not respond to
Electrical stimuli
• Muscular Reaction-ACIDIC
• MLI:Indicates time of death
CADAVERIC SPASM
• Muscle stiffening MARKED
• Does not occur
• BODY heat-Warm
• Muscles respond.
• ALKALINE
• MODE of DEATH-i,
e,homicide/suicide/accide4n0 t

41. Testing RIGOR MORTIS:
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 Tested by trying to lift
eyelids
 Depressing jaws
 Gently bending the
Neck
 Try flexing/extending
various joints of body.
Degree->absent/minimal/moderate/advanced/complete.
Distribution->patchy/complete

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Medico legal Importance:Rigor mortis
1) It is a sign Of Death
2) Its extent helps in estimating the time of death.
3)It indicates the position of body at the time of Death.

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TIME OF DEATH
Best done at scene,sooner the better.
Worst estimate is done at the time of autopsy.

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KEY QUESTIONS;
?When was person last seen alive?
?When was body found dead?

45. DISCUSSION
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THANK YOU

46. 46
References:
THE ESSENTIALS OF FORENSIC MEDICINE AND
TOXICOLOGY by K.S.NARAYAN REDDY.
TEXT BOOK OF FORENSIC MEDICINE BY KRISHNAN
VIJ.
BERNARD KNIGHTS FORENSIC PATHOLOGY.

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Appendix

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Appendix