Postmortem changes and Time Of Death

Immediate (Somatic death):

1. Insensibility and loss of voluntary power
2. Cessation of respiration
3. Cessation of circulation

Early (Cellular death):

1. Skin:

• Pallor mortis
• Drying
• Loss of elasticity

2. Face:

• Expressionless (relaxed facial muscles)
• Moustache/beard/nails don’t grow (false impression due to shrinkage of skin)

3. Eye:

• 

  Loss of corneal reflex

• Decreased in i.o.t and softening of eyeball (like rotten tomato; normal like unripe tomato)
• Opacity of cornea: Due to drying (delayed by 2 hours if eyelid closed)
• Tache noir Sclerotique: If death occurs with eyes open, the open part dries up (non-functioning tear gland) and gives a brownish black horizontal band of discoloration (a film of cell debris and mucus on sclera on each side of iris from yellow → brown → black)
• Pupils: slightly dilated; later constrict with rigor mortis onset; react to atropine and serine for upto hour; shape change with pressure
• Retinal vessels: kevorkian sign (segmentation of blood columns)
• Chemical change: Steady increase in K+ in vitreous humor upto 100 hrs

4. Primary flaccidity of muscles (As long as ATP available)

5. Algor mortis (Cooling of Death):

Mechanisms: By radiation and convection; evaporation (wet body or clothing); Conduction (body lying on a cold surface)

Sigmoidal curve of cooling:

• Initial maintenance (1/2 to 1 hour): Post-mortem plateau
• Relatively linear rate of cooling (for next 12 to 14 hours)
• Rapid slowing of cooling as body approaches environmental temperature

Sites of measurement: Rectum (except in sodomy), Peritoneal cavity, External auditory meatus, Nasal passages

Body temperature is assumed to be normal at death but may be:

• Subnormal: Collapse, CCF, Hypothermia, Hypothyroidism, Muscle relaxants, Cholera
• Raised: Fat/air embolism, Infections, Septicemia, Heat stroke, Pontine hemorrhage, Thyrotoxicosis, Emotional stress, Neuroleptics, CO poisoning, Cocaine/Heroin, Exercise

Importance: Estimation of time of death (Reliable only in cold and temperate climates)

• Duration of death = (Normal body temp. – Rectal temp.)/Rate of cooling
• 2 unknown factors in assessing the time of death: Actual body temperature at the time of death and Length of Plateau phase

Factors affecting rate of cooling:

a. Environmental factor

• Environmental temperature
• Air movement: Air movement accelerates cooling by promoting convection
• Humidity: Cooling is more rapid in humid air or water (better conductor of heat)

b. Cadaveric factor

• Body temperature at death
• Body size: Greater the BSA relative to mass, more rapid will be its cooling (Greater in children, lean body and elderly)
• Clothing and coverings: Insulate body and slow body cooling

6.       Livor mortis (Darkening of Death)/PM Hypostasis or Lividity:

Definition: Dark purple discoloration of skin resulting from gravitational pooling of blood in veins and capillaries in dependent parts of the corpse

Mechanism:

• Fluidity of blood due to stasis and Incoagulability (by ½-1 hr) due to release of fibrinolysins
• Pressure prevents formation of lividity (Contact pallor or Vibices): area contact with another body part or surface, tight clothing, jewellery
• Less marked in reduced blood & pigment (hemorrhage, anemia, wasting disease) and quick coagulation (lobar pneumonia)

Distribution: indicator of body position and contact with objects

• Supine: Front of neck → Entire back → Flanks and sides of neck→ Isolated lividity in front and sides of neck possible
• Prone: Loose connective tissue on front of the body
• Side and Back
• Inverted: head and neck; eyes may suffuse with numerous conjunctival hemorrhages
• Vertical: legs, hands, external genitalia
• Drowning: face, upper part of chest, hands, lower arms, feet and calves
• Well marked in earlobes and fingernail beds

Color: indicator of cause of death

• Pink: Refrigeration soon (Retention of oxyhemoglobin), Hypothermia, CN poisoning
• Cherry red: CO poisoning (carboxyhemoglobin)
• Grey to brown: Sodium chlorate, nitrates, aniline (methemoglobin)
• Bronze: Clostridium gas gangrene
• Bluish green: Hydrogen sulfide

Development: indicator of time of death

• Normally visible by ½ to 1 hour as dull red patches
• Delayed in anemic and may appear shortly before death in circulatory failure
• Patches increase in intensity and become confluent by 4 hours, to reach maximum extent and intensity by 12 hours (Primary lividity)
• Secondary lividity: Body moved within few hrs → Old patches disappear → New reappear on dependent parts after shifting the body
• Extent and time depends upon: Volume of blood in circulation and Duration of fluidity of blood

Fixation of lividity:

• Usually occurs by 12 hours (Rigor mortis compresses vessels) and repositioning the body will result in dual pattern of lividity (Primary distribution will not fade away and new will appear)
• Blanching by thumb pressure indicates it is not fixed

Bluish black hemmorhagic spots (Tardieu spots): Exclusively limited to areas of hypostasis as a result of mechanical rupture of subcutaneous capillaries and venules

Changes in PM lividity: after putrefaction sets in; purple → green → black → disappear

Externally: hypostasis must be differentiated from ecchymoses (contusion)

Trait	Hypostasis	Contusion
Incision	Small bloody point of divided arteries	Subcutaneous tissues infiltrated with blood

Internally: hypostasis must be differentiated from congestion

Trait	Hypostasis	Congestion
1.       Redness	Irregular; on dependent part	Uniform all over
2.       Mucous membranes	Dull and lusterless	Normal
3.       Exudate	No	May be seen
4.       Hollow viscus	Alternate stained and unstained areas according to position of coils – intestine and stomach	Uniform staining

7. Rigor mortis (Stiffening of Death):

Biochemical basis:

• Contraction: PM loss of integrity of sarcoplasmic reticulum allows Ca2+ ions to flood the contractile units
• No relaxation: Membrane disruption and lack of ATP

1. Begins 1-2 hours after death and takes further 1-2 hours to develop
2. According to Shapiro, rigor mortis develops simultaneously in all muscles, although changes are visible earlier in smaller masses than larger
3. Small muscles of eyelids, lower jaw, neck → Small distal joints of hands and feet → Larger proximal joints of elbow and knee

Effect of movement:

1. Before rigor mortis develops: body can be moved to any posture and rigor will fix in that posture
2. When rigor mortis developing: extremities can be moved and rigor, temporarily overcome, develops in new position (rigidity will be less in disturbed part)
3. When rigor mortis fully developed:  stiffness is broken permanently and rigid muscles may show postmortem ruptures

Fully developed rigor mortis:

• Stiffened body, shortened muscles, slightly flexed knees/hips/shoulders/elbows, markedly flexed fingers/toes
• Cutis anserine: Goose-flesh appearance of skin due to contraction of erector pilae muscle attached to hair follicles
• Testes may be drawn upto groin
• Semen may be forced out of seminal vesicles
• Pupils may be partially contracted
• If death during labor: contraction of uterus → expulsion of fetus
• Contracted myocardium: Not to be mistaken for hypertrophy

• 

  Secondary flaccidity of heart (Action of alkaline liquids produced by putrefaction): Not to be mistaken for ante-mortem dilation or dysfunction

Differential diagnosis:

1. Heat stiffening: More intense (Denaturation and coagulation of muscle protein)
2. Cold stiffening: Freezing of body fluids and solidification of subcutaneous tissue
3. Cadaveric spasm/Cataleptic rigidity/Instantaneous rigor

Trait	Rigor Mortis	Cadaveric spasm
Production:	Freezing and >65 c	Cannot be produced
Predisposing factors:	Nil	Sudden death, excitement, fear, exhaustion, nervous tension
Time of onset:	1-2 hrs after death	Instantaneous
Muscle stiffening:	Not marked; moderate force can overcome it	Marked; great force required
Muscle involved:	All (Both voluntary and involuntary)	Usually single group of voluntary muscles
Molecular death:	Occurs	Doesn’t occur
Body heat:	Cold	Warm
Electrical stimuli:	No response	Muscles respond
Medicolegal importance:	Time of death	Mode of death (Suicide, homicide or accident)- grip upon weapon, clothing, grass, etc.

Late (Decomposition and Decay)

1. Putrefaction

Definition: PM destruction of soft tissues of body by action of bacteria and endogenous enzymes of body and is entirely capable of skeletonizing the body

Factors influencing rate of putrefaction:

1. Delayed: Body cooling (Lean), Cold temperature, Chemical embalming, Exsanguination (because blood is the medium through which putrefactive organisms spread), Dry
2. Increased: Body cooling slow (Obese, heavy clothing), Ante-mortem infection, Hot temperature, Heavy insect activity, Moisture
3. Position: advanced in the dependent part (more blood)

Characteristic features:

Color changes:

• 1^st visible sign (12-18 hrs in summer and 1-2 days in winter): Greenish discoloration of skin of anterior abdominal wall most commonly in right iliac fossa (over cecum) due to sulphmethemoglobin formation (by H2S escaping into tissues from large intestine)
• Spread: Entire abdomen, external genitals → chest → neck → face → arms → legs
• Color: Green → Dark green → Purple → Dark blue
• Appearance: Patches → Confluent
• Marbling: Purple-brown network of arborescent markings on skin (Lividty → Putrefactive change → RBC hemolysis → Staining of vessel wall → Diffuses into tissues → Highlighting of superficial veins)

Foul smelling gases:

• Gases: CH3, H2, H2S, CO2, ptomaines (putrescine and cadaverine – detectable by cadaver dogs used to locate clandestine graves)
• Blisters of putrefaction (18-24 hrs): Blood stained fluid, air or liquid fat between epidermis and dermis
• Gas accumulation in tissues(18-36 hrs):
  • Crepitations, Swelling and Distension (Face, Swollen lips are everted, Protrusion of tongue, Abdomen, External genitals)
  • “Swiss-cheese” appearance of solid orgams
  • Rigidity due to inflation of tissues with gases
  • PM purge: Gaseous pressure expels blood stained froth exudates from mouth and nose which can be mistaken for antemortem hemorrhage
  • Skin slippage: Slippage of epidermis after light contact with body → Exposed dermis is shiny, moist, pink → Dries → Yellow parchmented appearance
  • Body hair and nails are loosened
  • Skin of hands and feet may come off in “glove & stocking” fashion

Liquefaction of tissues (5-10 days):

• Larynx & trachea → Stomach, intestine, spleen → Liver, lungs → Brain → Heart → Kidneys, bladder → Prostate, uterus → Skin, muscle, tendon → Bones

Putrefaction in water:

• Rate slower in water than in air. Rate (Warm,fresh water > Cold, salt water; Stagnant water > Running water)
• Submerged cadavers float with face down with head lower than trunk (Gaseous distention : face → neck → upper extremities, chest, abdomen, lower extremities)
• Washerman hands and feet

2.       Adipocere formation (Saponification)

Definition: Modification of putrefaction in which fatty tissues change into adipocere/grave wax/corpse wax (yellow-white, greasy, wax-like substance which is friable when dry)

Smell: Early (Ammonical) and After completion (Sweetish rancid)

Process: Fat hydrolysis → Fatty acids → Inhibit putrefactive bacteria (acidity) → + Calcium → Insoluble soap (brittle)

• Initiated by intrinsic lipases and continued by Clostridium perfringes leithinase
• Water requiring process (hydrolysis); water obtained from body tissues (dehydration)

Influence: Delayed (Cold), Hastened (Warm, moist, anaerobic condition, water submersion, burial)

Distribution: Fatty tissues; 1^st formed in subcutaneous tissue (commonly cheeks, breast, buttocks); rarely involves viscera like liver; admixed with mummified remains of muscles, fibrous tissues, nerves

Time required to begin: 4 to 5 days

Importance: Preservation of body (Personal identification and Injury recognition), Time since death

3.       Mummification:

Definition: Modification of putrefaction characterized by dehydration/drying and shriveling (shrinking) of cadaver, but the natural appearances and features of body are preserved

Mechanism: Evaporation of water

Necessary factors: Dry heat , Absence of moisture

Distribution: Begins in exposed area (Face, hands, feet) → Extends to entire body (internal organs as well)

Properties:

• Loss of weight: 60 to 70%
• Skin: shrinkage (may produce artefactual splits mimicking injuries), dry, brittle, leathery, brown to black
• Joints: Arms abducted, Elbow flexed, Fisted hands, Flexed lower limbs
• Internal organs: Shrunken, hard, dark brown and black, become a single mass

May disappear by: Moth activity, Putrefaction

Time required for completion: 3 months to years

Importance: Same as adipocere