EARLY STAGES OF DECOMPOSITION:
RIGOR MORTIS:
Muscular relaxation immediately after death is followed by the gradual onset of rigidity without shortening of the muscle. This is caused by the conversion of glycogen into lactic acid. The conversion of glycogen into lactic acid is attributed to metabolization of muscle for a short time after somatic death, or from products built up during the death event. As the pH decreases, there is a physical change in the muscle protoplasm. There is a cross-linking of actin and myosin by the presence
of excess lactic acid.
Perception of rigor is more rapid in the smaller muscles, however, all muscles are affected at a similar rate. The rigor is more evident in the short, smaller muscles earlier than in the longer, larger muscles.
Because this is a chemical process, heat accelerates and cold decelerated the process. Acidosis, uremia or other medical conditions promoting a lowered pH accelerate the process. Rigor is typically quantitated by “mild”, “early”, “moderate”, “and “complete” as a descriptive statement of degree of change. This is totally subjective and two observers may have different interpretations. Usually, perceived stiffness in motion of a joint is “mild”, difficulty requiring
force to move a joint is “moderate”, and having to use great force is “complete” rigor.
Once the physical change of the muscle is forced, that degree of change will not reoccur, so that if someone has broken the rigor, it will not reform to completion. If only partial rigor is present, some rigor will continue to form. Some conditions which affect rigor mortis include:
temperature
illness
activity before death
physical conditions where the body are found
MECHANISM ONSET MANIFESTED MAXIMUM DISAPPEARS
Physical change Immediate 1 - 6 hours 6 - 24 hours 12 - 36 hours
LIVOR MORTIS:
Livor mortis is the settling of blood to the dependant parts of the body. When cardiac activity stops, the hydrostatic pressure of the liquid blood causes it to settle to the lowest points within the body (depending on body position) and distend the dependant capillary bed. The color of the dependant part will depend on skin pigmentation and any additional compounds which may be present within the blood (i.e. carbon monoxide, etc.). The areas where the blood has settled will generally be
dark blue or purple in color. Livor begins at or very soon after death since it is a function of cardiac activity. However, stasis can occur to some extent in shock and some degree can be present even while the person is technically alive.
MECHANISM ONSET MANIFESTED MAXIMUM DISAPPEARS
Settling Immediate 2 - 4 hours 8 - 12 hours -----------------
Livor will not usually develop where there is pressure from clothing or objects. Therefore, important information regarding whether a victim was clothed for a period of time after death or if body position was changed can be gained from a careful inspection of the livor’s distribution.
Generally, time can best be supported from observation of livor and comparison with the accelerating or decelerating factors affecting that particular scene.
TARDEAU’S SPOTS/PETECHIAL HEMORRHAGES:
Accumulated blood which has settled in an area may cause capillaries in a small area to rupture so that circular or rounded areas of skin hemorrhage occur. These areas may range from pinpoint in size to 4 - 5 mm or larger in diameter. Tardeau spots usually refer to the larger petechia. Small pin point spots which are usually observed within the sclera (white portion) of the eyes and on the face may be suggestive of asphyxia.
ALGOR MORTIS:
Algor mortis refers to cooling of the body. Postmortem body temperature declines progressively until it reaches the ambient temperature. The metabolism of the body generates heat which is regulated to a narrow range. If the body cools at a uniform rate, then the rate of temperature decrease could be used to accurately determine the time of death. However, the body temperature is a narrow range, not a fixed temperature. Activity, illness, decomposition, infection and absorption of heat can
maintain or raise body temperature after death. The body cools by radiation (transfer of heat to the surrounding air by infrared rays), convection (transfer of heat through moving air currents) and conduction (transfer of heat by direct contact with another object). Therefore, many factors may influence the rate of heat loss. Careful consideration of the scene, clothing, victim size, activity and
physical factors must be considered in interpreting cooling rate. The Glaister equation is one formula used for determining the approximate time period since death based on body temperature. 98.4% - measured rectal temperature = approximate hours since death
1.5
Temperature has to be considered in light of all the scene data. For example, a deceased person who has been in a closed car all day with the sun shining on the car who is observed at night could not be expected to cool in a regular manner. In fact, an individual in this situation may well have a body temperature above “normal”. Several individuals who have studied the effects of body cooling suggest that the rate is not constant, but rather more heat is lost during the first few hours, then as the body begins to reach ambient temperature, the rate of heat loss slows.
OCULAR CHANGES:
DESCRIPTION EYES OPEN EYES CLOSED
Corneal film minutes several hours Scleral discoloration “tachy noir” minutes to several hours -------------------------- Corneal cloudiness 2 hours or less 12 - 24 hours Corneal opacity -------------------------- 3rd post-mortem day xophthalmos(Bulging) with gas formation with gas formation Endophthalmos(Retraction) with advanced decomposition with advanced decompositionn
FOOD IN STOMACH: (This information can be gained at autopsy)
SIZE OF MEAL TIME IN STOMACH (starts to empty within 10 minutes)
Light 1 _ - 2 hours
Medium 3 - 4 hours
Heavy 4 - 6 hours
Variations:
Liquid is digested faster than semi-solid food, which is digested fasted than solid food. Emotional state may also influence the rate of stomach emptying. Psychogenic pylorspasm prevents stomach emptying for several hours. Hyper motility may cause diarrhea.
VITREOUS POTASSIUM:
The body maintains an increased concentration of potassium in the intracellular fluid. This increase is 2- to 40 times the concentration of potassium within the plasma. This high concentration requires a balance between the electrical charges inside and outside the cell membrane and is maintained in this relatively high concentration be active metabolic forces that “pump” the electrolytes selectively across the membrane. A return to equilibrium occurs after death at a steady
rate because the pumping mechanism is no longer active and the cell wall becomes a semi-permeable membrane that allows the potassium to leak through the membrane to approach equilibrium. The leak is at a steady rate because of the mechanical limits of the membrane. This steady rate provides a built-in clock that allows a projection back to the time of death. An ideal sample, protected from most trauma is the vitreous fluid of the eye. Calculations are most accurate when samples are obtained
within 12 hours after death.
One formula developed for estimating the time of death based on a uniform potassium leak rate of 0.14 mEq/L/hr. is:
(7.14 x K+ concentration) - 39.1 = hours since death
Soon after this data was published the formula was found to be inapplicable for some locations and/or situations. It is suggested that your medical examiner determine the rate for your specific location.
Postmortem Tissue Changes:
Decomposition: Involves two major components. These components are:
Autolysis: The process by which digestive enzymes within the body cells break down
carbohydrates and proteins. Autolysis usually starts in the pancreas.
Putrefaction: The major component of decomposition which is due to bacterial activity.
Characteristics of putrefaction include:
1) Gas formation and bloating
2) Green discoloration of abdomen
3) Marbling along blood vessels-a brown black discoloration in blood vessels caused
by hydrogen sulfide gas
4) Blisters and skin slippage
5) Loss of hair and nails
Mummification: Drying of the body or its parts with “leather-like” changes. Mummification is characteristically seen on the tips of the fingers and nose. It can occur in as little as 1 - 2 days.
Skeletonization: Characterized by removal of soft tissue. Occurs largely as a result of insects and animals.
Adipocere: Formation of a waxy substance due to the hydrogenation of body fat. A moist, anaerobic environment is required for the formation of adipocere.
EXTENSIVELY DECOMPOSED/SKELETONIZED REMAINS:
Should be treated as any other scene involving careful examination and documentation of the scene, collection of evidence, etc.
The best approach is to plan ahead. Another day at this stage will probably not change the scene significantly, but could make the final conclusions better. Use the services of a forensic anthropologist if possible. The weathering of bones depends considerably on:
Buried or not buried
Climate
Moisture
Elevation
Terrain
Protection
Insect/animal/human intervention
Check weather bureaus for rainfall, temperatures, etc.
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