Some of the changes which occur after death are related to somatic death and some are related to molecular death. Accordingly, some of them are conspicuous immediately, some come early and the rest appear late.
1. Immediate changes —
(a) Stoppage of function of nervous system
(b) Stoppage of respiration
(c) Stoppage of circulation.
2. Early changes —
(a) Facial pallor
(b) Loss of elasticity of the skin with decrease in the facial creases
(c) Primary relaxation of the muscles
(d) Contact pallor and contact flattening
(e) Changes in the eye
(f) Cooling of the body
(g) Postmortem staining (lividity)
(h) Rigor mortis or postmortem rigidity.
3. Late changes —
(a) Putrefaction or ordinary decomposition
(b) Adepocere change — a modified form of decomposition
(c) Mummification — another form of modified decomposition.
Stoppage of functions of nervous system
With death all functions of the nervous system cease. The subject has no sense. There is loss of both sensory and motor functions. There is loss of reflexes; no response and no tonicity of the muscles. Pupils are widely dilated.
Stoppage of respiration
With somatic death, there is total stoppage of respiration which can be established by the following tests:
1. Inspection — No respiratory movement will be visible.
2. Palpation — Respiratory movement can’t be appreciated.
3. Auscultation — No breathing sound can be heard from any part of either lung.
4. Feather test — If a downy feather or a few cotton fibres are held in front of nose, then, if respiration is continuing, it will rhythmically move with the inspiration and expiration. If respiration has ceased then, there will be no movement of the feather or the cotton fibres.
5. Mirror test — The shining surface (reflecting surface of a mirror) is held in front of the nose and mouth of the person. If respiration is continuing then the shining surface of the mirror will partly become hazy due to condensation of the moisture of the expired air on the cold shining surface of the mirror. If respiration has ceased then, there will be no hazy appearance of the surface of the mirror, for obvious reason.
6. Winslow’s test — A small bowl with water is placed over the chest of the subject with arrangement of some light rays falling on the surface of the water in the bowl. Slightest movement of the chest wall, even due to feeble respiration which cannot be appreciated as such, will disturb the plain of the surface of the water, which can be well marked from the rays of light reflected from the surface of water.
Stoppage of circulation
The following tests may be performed to know, if the circulation has ceased or is continuing —
1. Radial, brachial, femoral and carotid pulsations will be absent if the circulation has stopped. In case of very feeble circulation, these pulsations are very weak and may not be perceived.
2. Auscultation of heart — The whole precordial area and particularly the area over the apex is auscultated, for presence or absence of heart beat which is absent if circulation has ceased. When the circulation is feeble and when there is excessive deposition of fatty tissue over the area, auscultation may miss such heart beats.
3. Diaphanous or transillumination test — If, in a dark room the outstretched hand is held against some bright light-rays, then in presence of circulation, the hand will appear pinkish and transluscent. If circulation has ceased then, the hand will appear yellowish and opaque.
4. Magnus test — It is a very satisfactory layman’s test for circulation. Veins run superficial to the arteries. Ligature is applied on a finger sufficiently tightly to compress the superficial veins but not the deeper arteries. If circulation is continuing then, after while the part of the finger distal to the ligature will appear swollen and bluish due to venous obstruction and accumulation of the reduced blood in the distal part. If circulation has ceased then there will not be any such change.
5. Icard’s test — In this test, 1 ml. of 20% alkaline fluorescein solution is injected either in the dermis or subcutaneously. If circulation has not stopped then, in case of intra-dermal injection, the area of yellowish discolouration spreads locally and in case of subcutaneous injection, the dye travels to the distant parts of the body and yellowish discolouration appears in the conjunctiva.
6. Pressure test — In case the circulation is continuing, if pressure is applied on the nail of a finger then, it becomes pale but soon becomes red on release of the pressure. In case of cessation of circulation pressure causes paleness of the nail, which takes much more time to return to its normal colour on release of pressure.
7. Cut test — If circulation is continuing then, there is active bleeding from a small superficial cut. But if circulation has ceased then, such a small superficial cut may cause very minor degree oozing of blood but no free active bleeding.
8. Heat test — If a small area of the skin is brought in contact with some hot object, say of about 100°C, then, at the site of contact there will be blister formation surrounded by a red ring. If the period of contact is very short then, there may not be any blister formation but there will be redness over the area of contact. These happen if circulation is continuing. If circulation has stopped then these changes will not be there. Instead, the area of contact will become dry, firm without any redness and blister formation.
9. E.C.G. test — By E.C.G. test, very weak functions of the heart muscles and the electrical conductivity there, are detectable. In case of cessation of circulation, the E.C.G. curve is absent with presence only of flat line on the baseline without any elevation and depression.
EARLY CHANGES AFTER DEATH
1. Facial pallor — After death, due to stoppage of circulation, blood drains from the capillaries and small vessels, to big ones. This is why,generally the face appears pale and bloodless, but in case of agonising death and,where there is obstruction of venous return due to compression over the neck or below, as in case of strangulations etc., the face is congested and cyanotic.
2. Loss of elasticity of the skin with ironing of the facial creases — These occur due to loss of tonicity of the skin muscles including those of the face. The face looks younger.
3. Primary relaxation or flaccidity of the muscles — After death muscles loose their tonicity and become flaccid. Joints are loose and the chest wall flattens. During this stage of relaxation the muscular tissues are still alive ; their chemical reaction is still alkaline and they still respond to electrical stimuli.
4. Contact flattening and pallor — During the stage of primary relaxation of muscles of the body, the areas which remain in contact with the ground, become flat and the blood from vessels of these areas are pressed out. During the stage of rigor mortis, the areas continue to be flat, as rigor appears in those muscles in their flattened state and the drainage of blood from the vessels of the areas make the areas pale which continue to be so even after formation of postmortem staining in the surrounding areas.
Medicolegal importance – From the contact flattening and pallor, the position of the body in which it stayed for some time after death can be understood.
5. Changes in the eye —
(a) With death, the corneal and pupillary reflexes are lost. But the pupils still react for sometime to myotic and mydriatic agents. The pupils normally dilate moderately after death. The diameters are usually about 5 mm during life (range of the diameter of the pupils is 2-9 mm).
(b) With death, the eyelids usually close due to loss of tone of the muscles of the eyelids.
(c) Haziness of the cornea — This occurs in two phases, when the eyelids are not closed. (i) When the eyes are open, then, within about 15 minutes the corneas become hazy due to drying or dessication and deposition of dust and debris over them. This haziness is transient and passes off, if a drop of water is poured on the cornea, (ii) But the cornea becomes permanently hazy after bout 10-12 hours of death, due to decomposition.
(d) Shape of the pupils – Ordinarily, they are circular. But as after death, there is loss of tone and elasticity of the ciliary muscles, the shape of the pupil can be changed which may persist during the stage of rigor mortis of the muscles. As the nervous control over the pupils is lost after death, the sizes and shapes of the pupils of the two sides may be different. It has been already mentioned earlier that, the pupils respond to the application of the miotic and mydriatic agents for an hour or two after death.
(e) Loss of occular tension – Occular tension falls rapidly after death and within about half an hour it becomes zero.
(f) Taches Noire Scleroitiques – This is a change in the sclera which occurs when the eyes remain open. It is the result of drying and dessication of the exposed conjuctiva and the sclera underneath. Within 2-3 hours, the exposed white parts of the eyeballs become yellowish and within 2 – 3 days, the areas become brown. In the two sides, 4 such discoloured areas can be noticed, two in each eye. Each discoloured area is triangular in shape with the base on the limbus, the apex at the lateral or medial canthus and the two other sides of the triangle are formed by the margins of the upper and lower eyelids. These are situated on either sides of the cornea of each eye.
Changes in the retina – Several changes occur in the retina and the choroidal plexus, which start almost immediately after death (within some second) and continue for about 12 hours.
Within 10 to 15 seconds, the retinal veins appear segmented. For a minute or two, the segments in the veins have a tendency to shift towards the centre and then they become static.
For the first 2 hours, the retina appears pale and the area around the disc looks yellowish. Same change occurs around the macula,and the macula now is deeper in colour. The normal mottled reddish appearance of the choroidal plexus is retained till this period. Then the mottling appearance of the plexus gradually becomes hazy by about 3 hours after death and by about 5th hour, the mottling disappears with homogeneous appearance of the eye background. By then the area is pale in appearance. By 6th hour, the disc outline also becomes hazy. By now, the smaller vessels are not recognisable and only the large segmented vessels can be recognised. The yellowish discolouration expands, which reaches the periphery of the retina between 7-10 hours. The disc outline is blurred now. By 12 hours after death, the area for the disc can be known only by some convergent segmented vessels. After this period, nothing in the retina can be recognised except a dark brown spot representing the macula.
The changes occurring in the eyes are early changes. In ordinary practice, these changes do not come to much assistance for determination of time passed after death. No doubt, the changes in the retina maintain chronology. If those changes could be studied by an experienced ophthalmologist, then those could be good criteria for estimation of time of death for the first 10 -12 hours after death. Study of retinal changes require use of ophthalmoscope, and in practice it is never done yet, in any part of our country. Firstly, use of ophthalmoscope is considered a cumbersome process; secondly, the study requires some degree expertisation ; thirdly, for the first few hours after death, some other external changes like appearance and distribution of rigor mortis, postmortem staining, cooling of the body etc. may help to assess the time of death with more or less same degree satisfaction. Some internal findings also help directly or indirectly. No doubt, the earliest definite changes in terms of seconds and minutes is assessable from the segmentation of the vessels of the retina. But then, it is of minimum significance, from practical medicolegal necessity point of view, to know whether death of a person has occurred 30 seconds or 2 minutes back.
Changes in the eye other than those in the retina, are less important for the purpose of estimation of time of death.
COOLING OF THE DEAD BODY
The first medicolegal use of the recording of body temperature, it can be said, was made by Dowler (1849 – 50), the purpose being confirmation of death of a person. But today, recording of temperature of the dead bodies has its medicolegal importance in connection with determination of time of death.
Sometime after death the body temperature of the cadaver falls and after some hours, it tends to be equal to the temperature of its immediate environment.
The different ways of loss of the body heat
The fall of temperature of the cadaver occurs due to the facts that, after death there is no heat generation, due to loss of all physical, chemical and metabolic functions of the body and there is constant loss of the body heat untill it comes to the level of the environmental temperature, as the heat regulating centre is inactive.
Loss of the body heat occurs by way, of conduction, radiation and evaporation (a form of convection), when the body is in the atmospheric environment and by ways of conduction and convection when the body is in the water media.
Though Newton’s law says that, loss of heat of a body is directly proportional to the temperature difference between the surface of the body and its surrounding at an instant time, this theory is not useful in case of fixing up the rate of fall of body temperature of a cadaver because, the law is for a body in which there is no qualitative difference between the surface and the depth of the body, whereas in case of a dead body there are definite differences in quality of the different strata from the surface to the depth of the body. This brings a difference between the rate of fall of the body temperature at different hours after death. Previously, it was generally thought that, other factors remaining constant, the rate of fall of the body temperature is same all along after death, starting from the moment of death. This would give a simple (exponential) curve for the hourly fall of the body temperature. But in reality it does not happen so. After death the surface (outer core) temperature falls rather rapidly for some time. But during this period, the loss of heat from the depth (inner core) of the body is rather negligible. This is due to the thickness of the skin and the subcutaneous tissue which are very good insulator for heat. However, some hours after death, by the time there has been reasonable fall of the surface temperature, a constant rate of flow of heat from inside the body establishes. It is then, that the fall of temperature at the inner core of the body, achieves a regular and constant pattern. Thus, if we take into consideration the rate of fall of the inner core temperature of the body, then, we do not get actually a simple (exponential) curve for the fall of temperature. Instead, in such a case we get a sigmoid or inverted ‘S’ shaped curve. Such a curve is indicative of practically no loss of heat or fall of the inner core temperature for the first two or three hours, which in the curve is presented as the initial plateau. Then there is sharp fall of the temperature for about 9 to 12 hours. After this period the rate of fall again diminishes, as, by that time the body temperature (inner core) has almost come to the level of that of the environment. Thus, the last part of the curve, which represents the terminal phase of loss of body heat, runs slightly above the base line or the axis (where the axis represents the time lapsed after death in hour and the ordinate represents the body temperature or the body temperature in excess of the environmental temperature). For the purpose of estimation of time passed after death, the measurement of the inner core temperature is important and more reliable than the outer core temperature.
Site of the body used to record the inner core temperature —
1. Rectum -4″ above the anus
Methods of measurement of the inner core temperature — Chemical thermometer with graduation ranging from 0°C to 50°C is required. For measurement of the intra-rectal temperature, the bulb of the thermometer is introduced 4″ inside the rectum. For measurement of the intra-abdominal, subhepatic temperature, a small slit like incision is given on the right side of the abdominal wall in front and the bulb of the thermometer is inserted for 4” inside the abdomen through the incised opening. Hourly temperature is recorded without withdrawing the thermometer, so that, there will not be additional loss of temperature locally and thus there will not be wrong result.
Practical utility of the study of loss of the body heat for the purpose of estimation of time passed after death —
Hourly recording of the body temperature is of more value for the purpose of determination of the time of death in cold or temperate countries, where the difference between the body temperature at the time of death of the person and the atmospheric temperature at that instant is quite reasonable. For temperate countries, Marshall and Hore formula is applicable with reasonable satisfaction. The ideal conditions for the use of this formula are as follows:
(a) The atmospheric temperature should be around 60°F (15.5°C)
(b) The body should ideally be uncovered
(c) The limbs should be outstretched
(d) The formula gives different rates of fall of body temperature, for subjects of different body built.
In tropical countries, measurement of the body temperature is not a good criterion for the purpose of determination of the time of death, because, the difference between the body temperature during death and the atmospheric temperature is not very high. For this reason, Marshall and Hore formula is not applicable in our country except in some hilly regions and when the atmospheric temperature is low (nearing 60°F). For the rest of our country, the rate of fall of the body temperature is taken on an average to be about 0.4°C or 0.7°F, in summer, per hour.
Factors which influence the cooling of a dead body —
1. Atmospheric temperature — The more is the difference between the temperature of the dead body and the atmospheric temperature, the more is the rate of fall of the body temperature. Thus, other factors remaining constant, whatever may be this difference (i.e., whatever may be the atmospheric temperature) the total time taken for the dead body to come down to the atmospheric temperature will remain constant.
2. Media of disposal of the dead body — The rate of cooling of the dead body differs according to, whether it is in the atmospheric media or in the water media (as in cases of drowned dead bodies) or is under the ground (i.e. buried). Optimum cooling is earliest in water media and latest in buried dead bodies. The ratio of the rates of fall of the body temperature in the three media is, water: air: grave:: 4 :2:1. The rate is maximum in water because, there the loss of body heat is due to both conduction and convection, both being very efficient means of heat loss. The rate is moderate in air because, here the heat loss is due partly (not fully), to conduction (through the parts of the body which touches the ground or some other materials), partly by convection (i.e. evaporation of the body fluid), and partly by radiation (through the parts of the body which is not in contact with the ground or other substance. In a buried body, the only effective means of loss of body heat is by way of conduction.
3. Body built — A thinly built dead body loses heat rapidly. For an average built body, the rate of loss is moderate and for a fatty body the retention of the body heat is for the longest period. Roughly, for a thinly built body, the optimum loss occurs by about 20 hours, for an average built or moderately built body this time is about 30 hours and for a fatty body it is about 40 hours.
4. Sex — Female bodies retain body heat for a comparatively longer period. This is because of the preponderance of the subcutaneous fatty tissue in them which increases the insulating capacity of the subcutaneous tissue.
5. Age — Rate of loss of the body heat is comparatively more in cases of infants, young children and very old subjects, than in adults. This is so because, in these subjects, the surface area of the body is more in comparison to the body volume. So, heat loss in them occurs through a greater surface (compared to body volume), resulting in the higher rate of loss.
6. Clothings or coverings of the body — A body well covered with clothes retains the heat for a longer period. In this regard qualities of the clothings exert further influences.
7. Air movement — Better air movement over the surface of the dead body causes quick fall of the temperature, by way of increased evaporation of the body fluid.
8. Dry weather — Dry weather by itself promotes rapid heat loss, by way of promoting evaporation of the body fluid.
9. Position and posture of the body — In a body with outstretched limbs, the loss of the body heat is rapid because, in such a posture, a greater surface area of the body is exposed for the loss of the heat.
10. Post-mortem caloricity — There are certain factors which instead of promoting the process of cooling of the body, act in an way, so that, the body temperature is either high at the time of death or is. increased for some time after death, so that, at a particular time after death the body may appear disproportionately warmer than what it should have been. These conditions are —
(a) Post-mortem glycogenolysis — This is a compulsory phenomenon which occurs in all the dead bodies and which starts soon after death (actually continues from life to some time after death till glycogen for lysis is available). In an average adult, postmortem glycogenolysis produces upto 140 calories which can increase the body temperature at an instant time by 3.6°F or about 2°C Hence, so far the inner core temperature of the body is concerned, when the body is yet to lose heat due to the insulating subcutaneous tissue, there may be virtual rise of the temperature of the body.
(b) Causes of death —
(i) If death occurs due to infectious diseases or septicaemia, bacteremia then, there may be high temperature of the body at the time of death and there may even be postmortem production of heat by the action of the infective organisms.
(ii) When death is preceded by severe convulsion, that causes increase in the body temperature to a reasonable degree before death, as in case of death due to strychnine poisoning. In case of death due to tetanus, both infection and convulsion are responsible for the postmortem caloricity.
(iii) Death due to heat stroke — In case of death due to heat or sun stroke, there is hyperpyrexia at the time of death. Hence the temperature of the body may continue to be more than the usual normal, at and for some time after death.
(c) High atmospheric temperature — In tropical countries in summer, during the day hours, the atmospheric temperature may remain higher than the body temperature at death. In such a condition, during the peak hot hours of the day, the dead body may absorb some heat and the temperature of the body may even be more than the normal at death, if the body is laid exposed, under the sun particularly. However, when the day’s temperature falls and during the night hours, the body temperature also falls.
Medicolegal importances of cooling of dead body —
1. Cooling of the body is a sign of death
2. From cooling of the body, time of death of the dead can be roughly estimated.
However, as has already been pointed out, measurement of the body temperature for the purpose of estimation of the time of death is useful only in the cold or temperate countries, where the difference between the body and the atmospheric temperature is countable. This method of determination of time of death is not very useful in our country or in any tropical country. Further, during estimation of time passed after death, by this criterion, it must be remembered that, various factors influence, the rate of loss of body heat, after death. Even, a body left for 24 hours after death will be subjected to alteration of the atmospheric temperature during the day and night hours. This means that, if the body is not preserved at a particular temperature, then, it is subjected to the influence of even hourly fluctuation of the environmental temperature.
3. Early cooling of the dead body delays the processes of rigor mortis and decomposition. On the other hand, if the body heat is preserved well for a longer period then, both the processes of decomposition and rigor mortis start early.