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Thanatology: Types of Death, Post Mortem Changes - Forensic Medicine

May 30, 2023

Thanatology Types of Death, Post Mortem Changes - Forensic Medicine

The study of death and dying from a variety of reasons  including medical, physical, psychological, spiritual, ethical, and more, is known as Thanatology. 

Thanatology is used by experts from a wide range of professions, from doctors and coroners to hospice workers and grief counselors, to inform their work. Additionally, there are Thanatology experts who concentrate on a particular component of the dying process or work directly with those who are confronting their own death or the death of a loved one. 

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Types of Death

Somatic death or Clinical death

In this there is complete and irreversible stoppage of any of Bishop’s tripod of life components which includes

  • Heart – circulation.
  • Lung – respiration
  • Brain function.

Or  there is a loss of any one function and it leads to death or the Doctor declares the individual dead.

Molecular death or Cellular death

It Occurs within  1-2 hours after somatic death.

Bichat’s mode of death 

It Depends on the dysfunction i.e., may be respiratory, circulatory, or brain function.

  • Dysfunction of respiration leads to  Asphyxia.
  • Dysfunction of circulation leads to Syncope.
  • Dysfunction of brain function leads to Coma.

Asphyxia, syncope, and coma are examples of Bichat’s mode of death.

Atria mortis or Gateway of death

Stopping of only one component of Bichat’s tripod of life (respiration, circulation, or brain function) results in death. It is an example of somatic death.

Suspended animation or Apparent death.

In this, signs of life are reduced to a minimal level and resuscitation leads to survival. Causes of suspended animation are:

  • Prolonged anesthesia.
  • Newborn (most common).
  • Barbiturates poisoning.
  • Cholera.
  • Cachexia.
  • Concussion.
  • Drowning.
  • Electrocution.
  • Hypothermia.
  • Hyperthermia.
  • Sunstroke.
  • Shock.
  • Insanity.
  • Trance (voluntarily suspended animation seen in yoga practitioners).
  • Typhoid (enteric fever).
  • Morphine overdose.

Post-Mortem Changes  

Signs of death may be immediate, early, or late.

Early signs include:

  • Eye changes.
  • Algor mortis.
  • Livor mortis.
  • Rigor mortis.

Immediate signs include

  • 1st sign is insensibility (loss of sensation) and loss of voluntary power 
  •  There is stoppage of respiration and circulation.

Late signs include:

  • Decomposition signs.
  • Putrefaction.
  • Autolysis.
  • Mummification.

Early Signs:

Eye changes

A) Railroading Phenomenon or Cattle Trucking or Kevorkian Sign

The Retinal blood vessels appear segmented or fragmented. It is seen within a few minutes to one hour after death. It can be seen using an ophthalmoscope. It is the earliest eye sign and it is used to determine time since death (TSD). Before the Kervokian sign, corneal reflexes are lost, and the pupil is dilated.

The "Kevorkian sign" is the fragmentation or trucking of blood vessels and it is a crucial ophthalmoscopic finding. Within a few minutes of death, the Kevorkian sign appears and lasts for around an hour.

Kevorkian sign

 Kevorkian sign

B) Flaccidity of the Eyeball

Normal intraocular pressure is 20mmHg.Two hours after death, intraocular pressure drops to 0 mmHg. It is also used to determine time since death.

c) Tâche Noire Sclérotique

After death, if the eyelids are open and dust is present in the atmosphere, it will get deposited in sclera resulting in  formation of 2 brownish triangular shaped opacities on either side of the cornea which is known as Tache Noire Sclerotique. It occurs after 3-6 hours of  post-mortem and  is used to determine time since death.

Tâche noire sclérotique
D) Corneal changes

Normally the cornea is transparent but after 1 hour of death the cornea becomes Hazy. Whereas opacity of cornea occurs after 6 hours.

Corneal changes
Vitreous Humor Changes

It is the most important medium in the eye which resists putrefaction. There are no chemical changes in vitreous humor after putrefaction.It is the best medium for estimating time since death, as it is enclosed within the eyeball so bacteria cannot have access to it easily.

So, even in an advanced decomposed body, this medium is very helpful. Best parameter is vitreous potassium levels. There is  Linear increase in K+ and hypoxanthine. It has linear correlation with time since death. Two formulas used for finding time since death are Sturner's Formula and Madea's Formula.

Also Read: Pectus Excavatum: Causes, Symptoms, Risk Factors, Diagnosis and Treatment

Cooling of the body or Algor mortis 

It is seen within 15 minutes after death. In this the body core  temperature (BCT) decreases. Thanatometer is a chemical thermometer used to measure BCT in  post-mortem. It may be 25-30 cm. It can measure temperatures between 0-50°C. Ideal site for recording temperature is the rectum (rectal temperature is almost equal to BCT). 

Other sites include the inferior surface of the liver, external auditory meatus, nasal spaces, and the lower end of the esophagus. Graph illustrating the relationship between temperature and time post-mortem produces a sigmoid curve or inverted S-shape curve.

Cooling of the body or Algor mortis
  • Stage I: Isothermic phase.
  • Stage II: Steep decline.
  • Stage III: Gradual decrease.

Algor mortis  Occurs in 3 phases 

  • 1sr phase: Gradual decrease in BCT 
  •  2nd phase: Rapid decrease in BCT 
  •  3rd  phase: Gradual decrease in BCT · Shape of Algor mortis curve is Sigmoid.

Rate of fall of temperature is 0.4°C – 0.7°C / hr that is, in summer it is  0.4° C / hr and in winter it is 0.7° C / hr. Average fall of temperature  is 0.5 C/hr. By knowing the rate of fall, we can calculate time since death.

Post-Mortem Caloricity 

Normally, the body becomes cold within 15 mins after death [Algor mortis]· But, if the body remains warm for 1-2 hrs even after death, it is known as  Post-mortem caloricity. Whenever there is increased body core temperature  at the time of death, post mortem caloricity is seen. 

Increased body core temperature at death is seen in  conditions with increased Muscle contraction that is Tetanus, Strychnos Nux vomica poisoning exercises etc. Defective thermoregulation in the body is associated with Heat stroke, Pontine hemorrhage [have pyrexia, paralysis, pinpoint pupils] and  Septicemia.

Post-Mortem Staining 

It is Also known as post-mortem lividity, hypostasis, livor mortis, vibices, or suggillation. This stain is Present in dependent parts of the body i.e., areas that do not touch the ground but face towards the ground.

Post-mortem staining

Gravitational forces cause the pooling of blood in capillaries and venules so there is accumulation of deoxyhemoglobin blood in the skin causes a bluish-purple appearance there is Skin discoloration of rete mucosum of the dermis. 

This stain is absent in pressure parts of the body. It begins shortly after death, that is after 30 minutes. And it is visible for 2 hours after death. Maximum visibility is for 6-12 hours and fixation occurs after 7-8 hours.

Secondary lividity occurs when changing the position of the body before 7-8 hours leading to post-mortem staining in other areas of the body, it persists till decomposition. Decomposition changes the skin color to green.

Post-mortem staining in different positions

  • In Supine position → the back of the head, back of the neck, back of the chest, back of the leg is stained 
  • In Prone position → the  front parts of the body are stained.
  • In Hanging position → the  hands and feet are stained  i.e. show  glove and stocking pattern.
  • In Running water → no post-mortem staining.

Medical importance

It helps to determine time since death and determine the position of the body at the time of death and also Determine the cause of death (COD).

Color Presentation due to Different Causes

  • Carbon monoxide poisoning → Cherry-red.
  • Cyanide poisoning → Bright or brick red.
  • Hypothermia → Pink.
  • Hydrogen sulfide (H2S) → Blue green.
  • Opium → Black.
  • Phosphorus or potassium chlorate (KCLO3) → Chocolate brown.
  • Nitrites, nitrobenzene, aniline → Chocolate brown.
    • Aniline may produce a blue color.
    • Chocolate brown color formed due to methemoglobin.
  • Clostridium perfringens → Bronze.
  • Methanol poisoning → Purple.

Rigor Mortis or Cadaveric stiffening or Cadaveric Rigidity 

It is also known as cadaveric rigidity / Cadaveric stiffening . It gives muscle status after the death of a person. The decrease in ATP causes stiffening of the muscle. Rigor mortis is generalized, that is it is seen in both voluntary & involuntary muscles but it is first seen in  involuntary muscles.

Rigor Mortis or Cadaveric stiffening or Cadaveric rigidity

3 stages muscles undergo after death include:

  • Primary flaccidity phase or primary relaxation phase.
  • Rigor mortis.
  • Secondary flaccidity phase or secondary relaxation phase.

Primary flaccidity occurs during somatic death. Rigor mortis occurs during cellular death. Mechanism of rigor mortis is ATP depletion. Actin-myosin separation takes place in primary flaccidity. Lack of actin-myosin separation causes rigor mortis. 

Secondary flaccidity occurs when decomposition starts in this Actin and myosin filaments are broken down leading to separation. When rigor mortis starts, ATP decreases to 85% of the normal content. At maximum rigor mortis, ATP decreases to 15-30% of the normal content. 

Occurrence of Rigor Mortis in Muscles

It begins 1-2 hours after death. It is seen in all muscles whether voluntary or involuntary. 1st muscle affected is the myocardium. 1st external muscle affected is the upper eyelid muscle i.e., orbicularis oculi.Sequence in which external muscles are affected:

Eyelid muscles → Neck → Lower jaw → Muscles of face → Muscles of chest → Upper limbs → Abdomen → Lower limbs → Fingers and toes

Rigor mortis disappears in the same order that it appears. It will disappear first from the upper eyelid and last from the fingers and toes. 

Rule of 12

  • In the first 12 hours after death, rigor mortis appears in all body muscles.
  • In the next 12 hours, it persists in all body muscles.
  • In the next 12 hours, it disappears from all body muscles.
  • Rigor mortis appears and disappears within 36-48 hours after death, thereby aiding in the determination of TSD.

Rigor Mortis in a Fetus

In fetuses of less than 7 months of age, rigor mortis is absent because the Actin and myosin filaments have not developed. Rigor mortis' appearance is  according to seasons. In summer, it is seen in 18-36 hours whereas In winter, it is seen after  24-48 hours. 

Rigor Mortis Appears in Wasting Diseases

In this Muscle mass is thin with decreased ATP storage it is seen in Diseases such as cholera, TB, cancer, cachexia, and typhoid. In this there is Early onset of rigor mortis with short duration. 

Rigor Mortis appears  in Violent Death

In Cases such as cut throat injury or firearm injury leads to appearance of rigor mortis in violent death. It has Early onset rigor mortis with short duration.

Rigor Mortis Appearance in Thick Muscle 

There is Increased ATP storage and it has Late onset of rigor mortis.

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Causes of Muscle Stiffening after Death                    

  • Rigor mortis.
  • Heat stiffening.
  • Cold stiffening.
  • Gas stiffening.
  • Cadaveric spasm.

Heat Stiffening 

It is Also known as boxing attitude or pugilistic attitude or fencing attitude. It occurs when Surrounding external temperature is ≥ 65°C. Mechanism involves the coagulation of muscle protein. Normal rigor mortis is not seen. Heat stiffening Persists till decomposition occurs.

Heat stiffening

Cold Stiffening 

It occurs when Surrounding external temperature is ≤ -5°C. Mechanism involves freezing of the body fluid and hardening of the subcutaneous tissue.In warm temperature, cold stiffening disappears. In this Normal rigor is present.

Gas Stiffening 

Occurs due to  intense accumulation of gas. It is Seen with decomposition. During decomposition, there is excess gas production · These gasses get accumulated in the body, resulting in stiffness of the body.

Gas stiffening

Cadaveric Spasm 

It is Also known as cataleptic rigidity or instantaneous rigor. Mechanism involves ATP depletion. Muscles remain contracted for lifetime and remain rigid and stiff after death. It Occurs immediately after death. Primary relaxation is absent whereas Secondary relaxation is present. It is An exclusively ante-mortem event.

Cadaveric spasm

Causes of cadaveric spasm:

  • Asphyxial death.
  • Brain injury.
  • Cerebral injury.
  • Drowning.
  • Dinitrocresol poisoning.
  • Excitement.
  • Fear.
  • Firearm e.g., in suicide.

Differences between cadaveric spasm and rigor mortis

 Cadaveric spasmRigor mortis
TimeImmediately after death.1-2 hours after death.
MusclesMainly involves voluntary muscles.
Generally, it involves a short group of muscles e.g. hand muscles.
Involves both voluntary and involuntary muscles.
Primary relaxationAbsent.Present.
Molecular deathAbsent.Present.
Electronic stimuliResponse present.Response absent.
ImportanceDescribes the manner of death.Determines TSD.

Late changes

In these changes the body gets decomposed. Decomposition occurs by Two mechanisms: autolysis and putrefaction.


It is a process in which Body enzymes cause cell lysis. Examples of autolytic changes:

  • Clouding of cornea – 1st external change.
  • Changes in brain glandular tissue – 1st internal change.

Aseptic autolysis involves the mummification of the fetus in intrauterine death.


It is Stimulated by bacterial activity. Most common bacteria involved is Clostridium welchii or Clostridium perfringens. Most common enzyme involved is lytic lecithinase.

 Putrefaction occurs in Three stages of change:

  • Color change.
  • Gas formation.
  • Liquefaction of tissue.
Color change

1st internal/overall change of putrefaction is reddish-brown discoloration of aortic intima. 1st external change is green discoloration of the right iliac fossa.


Bacteria forms hydrogen sulphide. Cecum located beneath the right iliac fossa has maximum bacterial activity. Skin lies superficial to the cecum. Sulphur combines with hemoglobin to form a green color compound. In summer, discoloration starts in 12-18 hours. In winter, discoloration starts in 1-2 days.

 decomposition green discoloration of body

In this there is Discoloration of prominent superficial veins to green-brown color which Corresponds to the vascular channel.

Mechanism: Clostridium welchii bacteria form hydrogen sulfide gas in the superficial veins with the formation of green, brown sulphahemoglobin.it Starts in 24 hours and is Prominent in 36-48 hours. It helps in determining TSD. It is Seen in the chest, shoulder, abdomen, and thigh.

Gas production:

Predominant gas produced in decomposition is H2S.This gas gets accumulated in the body resulting in stiffening known as  gas stiffening · Gas in skin at dermo – epidermal Junction results in Blister Formation

gas stiffening
postmortem blister

It takes 5-10 days. Loosening of hair/ nails, occur in 3-5 days and kin around the hands & legs peel off i.e Degloving/Destocking pattern is seen in 5-10 days

 Post-mortem purge 

  • Gas formation during decomposition leads to the expulsion of blood-stained froth and gastric contents from the nose and mouth.
  • Seen after 2-3 days.

Post-mortem luminescence 

Body emits light after death. Causes of post mortem luminescence are:

  • Bacterial e.g., photobacteria presence.
  • Fungal e.g., Armillaria, Ram’s bottom.
 Casper’s  Dictum  

  It is about rate of putrefaction in different medium · Rate of putrefaction is compared b/w 3 imp medium. This Formula was proposed by Taylor. It Shows the relationship between the rate of decomposition in air, water and soil (earth).

  • Air > Water > Earth.

If decomposition in the air takes 1 week, it will take 2 weeks in water and 8 weeks in soil. Air has the fastest rate of decomposition.

 Putrefaction sequence 
  • 1st organs to decompose are the larynx and trachea due to their direct contact to air.
  • Followed by (in order):
    • Stomach, spleen, and small intestine.
    • Liver and lung.
    • Brain, heart, kidney, uterus.
    • Skin, muscle, tendon, bone/tooth.
  • Non-gravid uterus is the last organ to decompose in females.
  • Prostrate is the last organ to decompose in males.
  • The overall last organ to decompose is bone/tooth.
Important points of putrefaction 
  • Liver shows gas formation up to 24-36 hours i.e., foamy liver or honeycomb liver.
  • Optimum temperature for decomposition is 21-38°C.
  • Decomposition starts at > 10°C.
  • Poisons inhibiting putrefaction include:
    • Strychnine.
    • Metallic poison e.g. arsenic, antimony, thallium.
    • Carbon monoxide.
    • Cyanide.
    • Carbolic acid.
  • The 1st amino acid that disappears from bone in decomposition is proline.
  • The 2nd amino acid to disappear is hydroxyproline.
  • Last amino acid to disappear to glycine.
  • Bones that are 100 years old have < 7 amino acids.
Modification of Putrefaction:
Adipocere or saponification or grave wax

Also known as  Grave wax/ Saponification . The Fat in the body gets converted into fatty acids;  and combines with Calcium  in the body & forms insoluble wax like substances i.e (SOAP) adipocere.  

When an adipocere is formed, it is preserved for a longer time. It is Hydrolysis and hydrogenation of fat. Factors required for conversion are  Warm, moist climate, Clostridium welchii (lecithinase), Intrinsic lipases (lipases within the body). The predominant fatty acid is Palmitic acid. Acidic medium Inhibits the multiplication of bacteria (Further putrefaction is inhibited),Hence the body is preserved, Smell of adipocere is  Ammoniacal.

Appearance of adipocere :

Fresh adipocere - greasy and it  Looks like rancid butter 

Old adipocere-  dry,hard, yellow and brittle 

Time required for adipocere formation is 3 days to 3 months and it is Absent in fetuses of less than 7 months.

old adipocere

Medical importance

It helps to Describe the climate at time of death and Determination of Time since death and helps in Preservation of the dead body for easy identification.


When the body is exposed to dry / hot climate, drying & dehydration of the body occurs resulting in mummification, in this the Body size is shrunken , There is loss of weight that is more than 70% weight is lost. It has No specific smell / Odourless. It takes 3 months – 12 months to occur. Mummification is also seen in intrauterine death of fetus, when there is intact membranes & deficient blood supply. Arsenic & Antimony favor mummification. It is an Important feature of intrauterine death.

  • Medical importance:
    • Describes climate at the time of death.
    • Determination of TSD.
    • Identification is comparatively very easy.
Embalming or Tanatopraxia                        

Artificial method of preserving the body by injecting anti  septic's & preservatives ·

 Exhumation is lawful digging of the body · Ideal Time for embalming is less than  6 hrs after death (Very effective)

Composition of embalming fluid


  • Formalin.
  • Formaldehyde.
  • Methanol.


  • Phenol.

Wetting agent

  • Glycerine.
  • Glycerol.


  • Sodium citrate.


  • Sodium bicarbonate.
  • Sodium carbonate.
  • Sodium chloride.


  • Water.

Ethanol is not a part of embalming fluid.

Embalming methods

  • Arterial.
  • Cavity.
  • Surface embalming (not commonly used).
  • Best method is a discontinuous injection and discontinuous drainage.
  • High pressure/low volume method also used.
  • Best vessel is the femoral artery.
  • Embalming is always done after a post-mortem or receiving the death certificate.

Ante-mortem vs Post-mortem 

Protein (mainly, albumin).
Enzymatic/Vital reactionPresent.Absent.

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