1. Chemical and biochemical
changes

3. Medic- legally death is not only the absence of life-it is
defined
as permanent and irreversible
cessation of functions of the
three interlinked vital systems
of the body(tripod of life),
Namely: the nervous, circulatory,
and respiratory systems.

5. • Estimation of time since death can directly or indirectly help
to find out time of assault , by additional findings related
with the stage of healing of an injury, which is equal to
period for which the victim survived after sustaining the
injury.
• This is helpful for the investigating officer to locate an
accused or verify any alibi of the accused.

6. • MECHANISM: It is bluish-purple or reddish-purple
discolouration due to capillo-venous distension with
blood at the undersurface of skin of the dependent parts
of the body for settling of blood in those areas due to the
pull of gravity, when circulation to keep the blood in
motion ceases.
• Bluish discoloration is NOT due to asphyxia
• In dead bodies o₂ dissociation continues and there may
be reflux of deoxygenated venous blood in capillaries
and dependent parts, is reddish purple
• Sites: Body surface & internal organs.
• It appears in about 1-2hours & fully established in 6-12
hours
• Fixation of levidity: The fluid may be displaced but there

8. • Sign of death
• Time of death: 1-2 hours: It appears
• 6-12hours: fully established
• Position of the body can be determined: eg. In case of hanging, the
PMS will be present on lower limbs & lower part of upper limbs.
• Colour of staining can indicate cause of death:
Due to CO poisoning- cherry red or pinkish
In cyanide poisoning- Brick red
Phosphorous,pot.chlorate,nitrate and aniline- dark brown
H₂s poisonig greenish blue
septicaemia: bronze
Due to exposure to cold- bright red due to non utilisation
of oxygenated blood,due to lack of metab.
Drowning- red,formation of oxyHb in blood capillaries,due to
absorption of O₂ through the body surface

10. • It is that state of the muscles (involuntary & voluntary) of a
dead body when they become stiff or rigid with some degree of
shortening.
• After death there is breakdown of ATP, stiffening of muscles
occur when ATP is reduced to <85% . If glycogen is available
there is re-synthesis of ATP
• Once the muscle glycogen is exhausted re-synthesis is not
possible and muscle loose elasticity, softness and extensibility
due to formation of viscid acto-myosin complex.
• Since Calcium is not available , actomyosin complex become
semi permanent till it is broken or destroyed due to
decomposition.
• *How to test for rigor mortis

11. • Sequence of appearance:
• 1st in the heart (left ventricle)after 1 hour small
muscles of face after 3-5 hours upper limbs
lower limbs within 5-7 hours fully established in 12
hours.
• RULE OF 12:
• The approximate time after death can be estimated using
the appearance & disappearance of rigor mortis. It fully
appears in 12 hours, persists for another 12 hours and
disappears in te next 12 hours.
• 12 + 12+ 12 = 36 hours

14. • There is decomp. of proteins by putrefying
bacteria resulting in production of
amines(purescine and cadaverine)having putrid
odour.
• Cl. Welchii is responsible for decomposition.
• H₂S,CO₂,CO,NH₃,marsh gas are produced.
• After death at the ileocaecal zone Cl.
Welchii,invade throgh the intestinal wall and
reach bvs,breaking tissue structure producing
H2S gas which combines withHB to form
sulphmethaemoglobin which discolours.
• Diffusion of gases causes spreading of

16. • Invasion of blood vessels by by the organisms and
production of H₂S gas and formation of
sulphmethaemogloin causing greenish brown staining of
the inner walls of the vessels.
• This makes superficial veins prominent and colourful
• This gives a marbled appearance of skin.
• Prominent after 36-48 hours.

18. • Formation of soft,whitish,crumbly,waxy and greasy
material occuring in fatty or fat containing tissues of dead
body.
• Consists of fatty acids formed due to hydrolysis and
dehydrogenation of body fats.
• Initially the process needs water and body utilises its
fluid and hence other soft tissues become mummified.
• Normal body fat contains 0.5%FFA but in adepocere it is
70%

19. • Blood pH falls due to glycogenolysis,glycolysis,terminal
accumulation of co₂,lactic acid,phosphoric acid and
splitting of a.a. and f.a.
• Blood pH rises again during secondary relaxation due to
accumulation of ammonia.
• Soon after death,plasma and RBC chloride levels are
equal,by 3rd day level drops to half due to extra vascular
diffusion and by dis Mg level rises 8fold.
• 12hrs after death,level of a.a nitrogen in blood is about
10mg%,NPN 40mg% and creatine 10mg%.

20. • Levels of NPN,amino acid nitrogen
and phosphorus levels in CSF are
same as in blood.
• CSF analysis for time of death is
more dependable than that of blood
because the levels of the
constituents in CSF are less
vulnerable to variation.

21. • Biochemical estimation of some of the
constituents of vitreous humor. These are:
• LEVEL OF ASCORBIC ACID: level falls after death
• LEVEL OF PYRUVIC ACID: level falls after death
• LLEVEL OF POTASSIUM: level rises to a moderate extent
constantly,for about 100hrs after death.

23. • Growth of facial hair occurs at the rate of 0.4 mm/day.
• Therefore by measurement of facial hair in subjects
habituated of shaving it can be said for what period he
survived after his last shave.

25. • From the state of digestion of food in stomach and
approximate quantity of food emptied from
stomach, it can be estimated the time after which
the person survived after taking his last meal.
• Therefore if the time of last meal is known
approximate time of his death can be made out
indirectly.
• Carbohydrate passes out earliest from stomach.
• Protein take some more time
• Fat empties last.

26. • Normal emptying time for an average Indian mixed diet:
• 1)half of food to pass through
pylorus-45 min/1 hr
• 2) half of rest-1/2 hr
• 3) half of rest-3rd hr
• 4) remains within an hour
• So, total emptying time- 4-5 hrs.

27. • Digested food residue reaches:
• Ascending colon by: 6-8 hrs
• Left flexure of transverse colon: 9-10 hrs
• Pelvic colon by: 12 hrs
• Here food remains as faeces for upto 12 hrs.

28. • Radioactvie carbon is deposited in living tissues and
maintains a near equilibrium level all along the life.
• After death there is no further deposition of c₁₄ and its
conc. gradually decreases.
• In bone it reaches its half life in about 5600 years and
estimation of bones of a person who died several years
back,to study the strength of C ₁₄ in the bones may give
some idea when the person died.